JP7573399B2 - Resist composition and method for forming resist pattern - Google Patents

Description

The present invention relates to a resist composition and a method for forming a resist pattern.

In lithography, for example, a process is performed in which a resist film made of a resist material is formed on a substrate, the resist film is selectively exposed, and a development process is performed to form a resist pattern of a predetermined shape on the resist film. A resist material in which the exposed portion of the resist film changes to a property that dissolves in a developer is called a positive type, and a resist material in which the exposed portion of the resist film changes to a property that does not dissolve in a developer is called a negative type.
In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, the advancement of lithography technology has led to rapid progress in miniaturization of patterns. In general, the miniaturization method involves shortening the wavelength (higher energy) of the exposure light source. Specifically, ultraviolet rays such as g-line and i-line have been used in the past, but currently mass production of semiconductor elements is being carried out using KrF excimer lasers and ArF excimer lasers. In addition, EUV (extreme ultraviolet), EB (electron beam), X-rays, and other light sources with shorter wavelengths (higher energy) than these excimer lasers are also being studied.

Resist materials are required to have lithography properties such as sensitivity to these exposure light sources and resolution capable of reproducing patterns with fine dimensions.
As a resist material that satisfies such requirements, a chemically amplified resist composition that contains a base component whose solubility in a developer changes due to the action of acid, and an acid generator component that generates acid upon exposure, has been used so far.
For example, when the developer is an alkaline developer (alkaline development process), a positive-type chemically amplified resist composition generally contains a resin component (base resin) whose solubility in an alkaline developer increases under the action of an acid, and an acid generator component. When a resist film formed using such a resist composition is selectively exposed during resist pattern formation, an acid is generated from the acid generator component in the exposed area, and the polarity of the base resin increases under the action of the acid, so that the exposed area of the resist film becomes soluble in an alkaline developer. Therefore, by performing alkaline development, a positive pattern is formed in which the unexposed area of the resist film remains as a pattern.
On the other hand, when such a chemically amplified resist composition is applied to a solvent development process using a developer containing an organic solvent (organic developer), the solubility in the organic developer decreases relatively as the polarity of the base resin increases, so that the unexposed parts of the resist film are dissolved and removed by the organic developer, and a negative resist pattern is formed in which the exposed parts of the resist film remain as a pattern. The solvent development process that forms a negative resist pattern in this way is sometimes called a negative development process.

Up until now, as the base resin of a chemically amplified resist composition, for example, polyhydroxystyrene (PHS) having high transparency to KrF excimer laser (248 nm) and resins in which the hydroxyl groups are protected with acid-dissociable dissolution inhibiting groups (PHS-based resins) have been used. Also, for example, for ArF excimer laser (193 nm), resins in which the hydroxyl groups in the carboxyl groups of (meth)acrylic acid are protected with acid-dissociable dissolution inhibiting groups ((meth)acrylic-based resins) have been used (see, for example, Patent Document 1).
Mainly used examples of the acid-dissociable, dissolution-inhibiting group include so-called acetal groups, such as chain ether groups typified by a 1-ethoxyethyl group or cyclic ether groups typified by a tetrahydropyranyl group, tertiary alkyl groups typified by a tert-butyl group, and tertiary alkoxycarbonyl groups typified by a tert-butoxycarbonyl group.

Furthermore, a wide variety of acid generator components have been proposed for use in chemically amplified resist compositions. Known examples of acid generators include onium salt-based acid generators such as iodonium salts and sulfonium salts, oxime sulfonate-based acid generators, diazomethane-based acid generators, nitrobenzylsulfonate-based acid generators, iminosulfonate-based acid generators, and disulfone-based acid generators.
Among these, onium salt acid generators are widely used, and those having an onium ion such as triphenylsulfonium in the cation moiety are mainly used. In the anion moiety of these onium salt acid generators, an alkylsulfonate ion or a fluorinated alkylsulfonate ion in which some or all of the hydrogen atoms in the alkyl group are substituted with fluorine atoms is generally used.

Incidentally, with the current trend toward higher integration of LSIs and faster communication speeds, there is a demand for increased memory capacity, and further miniaturization of patterns is rapidly progressing. However, while lithography using electron beams or EUV aims to form fine patterns of several tens of nanometers, there are still many issues, such as low productivity, and there are limitations to the technology of microfabrication.
In response to this, in addition to miniaturization, development is underway on three-dimensional structure devices that aim to increase memory capacity by stacking cells together.

JP 2003-241385 A

The manufacturing of the three-dimensional structure device includes a process of forming a thick resist film on the surface of the workpiece that is thicker than conventional resist films, for example, 5 μm or thicker, to form a resist pattern and then perform etching or the like. When a chemically amplified resist composition is used here, the thicker the resist film, the more difficult it is to maintain sensitivity during exposure, and the resolution in development decreases, making it difficult to obtain the desired resist pattern shape. Another problem is that the thicker the resist film, the more likely it is that cracks will occur in the resist pattern.

The present invention has been made in consideration of the above circumstances, and aims to provide a resist composition that can form a thick resist film, is less likely to crack, and has good sensitivity, as well as a method for forming a resist pattern using the resist composition.

In order to solve the above problems, the present invention employs the following configuration.
That is, a first aspect of the present invention is a resist composition that generates an acid upon exposure and whose solubility in a developer changes due to the action of the acid, the resist composition comprising: a base component (A) whose solubility in a developer changes due to the action of an acid; and an ionic liquid (Z), and the resist composition has a solids concentration of 25 mass % or more.

The second aspect of the present invention is a method for forming a resist pattern, comprising the steps of forming a resist film on a support using the resist composition according to the first aspect, exposing the resist film, and developing the exposed resist film to form a resist pattern.

The present invention provides a resist composition that can form a thick resist film, is less likely to crack, and has good sensitivity, as well as a method for forming a resist pattern using the resist composition.

In this specification and claims, the term "aliphatic" is a relative concept to aromaticity and is defined as meaning a group, compound, etc. that does not have aromaticity.
Unless otherwise specified, the term "alkyl group" includes linear, branched and cyclic monovalent saturated hydrocarbon groups. The same applies to the alkyl group in an alkoxy group.
Unless otherwise specified, the term "alkylene group" includes linear, branched and cyclic divalent saturated hydrocarbon groups.
The term "halogenated alkyl group" refers to an alkyl group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and examples of the halogen atoms include fluorine, chlorine, bromine and iodine atoms.
The term "fluorinated alkyl group" or "fluorinated alkylene group" refers to an alkyl group or alkylene group in which some or all of the hydrogen atoms have been substituted with fluorine atoms.
The term "structural unit" refers to a monomer unit that constitutes a polymeric compound (resin, polymer, copolymer).
The phrases "may have a substituent" or "may have a substituent" include both cases where a hydrogen atom (-H) is replaced with a monovalent group and cases where a methylene group (-CH ₂ -) is replaced with a divalent group.
The term "exposure" is intended to include any concept including irradiation with radiation.

The "base component" is an organic compound having a film-forming ability, and preferably has a molecular weight of 500 or more. When the molecular weight of the organic compound is 500 or more, the film-forming ability is improved, and in addition, it becomes easier to form a nano-level resist pattern. The organic compounds used as the base component are broadly classified into non-polymers and polymers. As the non-polymers, those having a molecular weight of 500 or more and less than 4000 are usually used. Hereinafter, the term "low molecular weight compound" refers to a non-polymer having a molecular weight of 500 or more and less than 4000. As the polymers, those having a molecular weight of 1000 or more are usually used. Hereinafter, the terms "resin", "polymer compound" and "polymer" refer to a polymer having a molecular weight of 1000 or more. The molecular weight of the polymer is the weight average molecular weight calculated in terms of polystyrene by GPC (gel permeation chromatography).

The term "structural unit derived from an acrylate ester" refers to a structural unit formed by cleavage of the ethylenic double bond of an acrylate ester.
An "acrylic acid ester" is a compound in which the hydrogen atom at the terminal carboxy group of acrylic acid (CH ₂ ═CH—COOH) is substituted with an organic group.
In the acrylic acid ester, the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. The substituent (R ^α0 ) substituting the hydrogen atom bonded to the carbon atom at the α-position is an atom or group other than a hydrogen atom, and examples thereof include an alkyl group having 1 to 5 carbon atoms and a halogenated alkyl group having 1 to 5 carbon atoms. In addition, it also includes an itaconic acid diester in which the substituent (R ^α0 ) is substituted with a substituent containing an ester bond, and an α-hydroxyacrylic ester in which the substituent (R ^α0 ) is substituted with a hydroxyalkyl group or a group in which the hydroxyl group of the hydroxyalkyl group is modified. The carbon atom at the α-position of an acrylic acid ester refers to the carbon atom to which the carbonyl group of acrylic acid is bonded, unless otherwise specified.
Hereinafter, an acrylic ester in which the hydrogen atom bonded to the carbon atom at the α-position is replaced with a substituent may be referred to as an α-substituted acrylic ester. In addition, acrylic esters and α-substituted acrylic esters may be collectively referred to as "(α-substituted) acrylic esters."

The term "structural unit derived from hydroxystyrene" refers to a structural unit formed by cleavage of the ethylenic double bond of hydroxystyrene. The term "structural unit derived from a hydroxystyrene derivative" refers to a structural unit formed by cleavage of the ethylenic double bond of a hydroxystyrene derivative.
The term "hydroxystyrene derivative" refers to a hydroxystyrene derivative in which the hydrogen atom at the α-position of the hydroxystyrene is replaced by another substituent such as an alkyl group or a halogenated alkyl group, and includes derivatives thereof. Examples of such derivatives include hydroxystyrene in which the hydrogen atom at the α-position may be replaced by a substituent, in which the hydrogen atom of the hydroxyl group is replaced by an organic group; and hydroxystyrene in which the hydrogen atom at the α-position may be replaced by a substituent, in which a substituent other than a hydroxyl group is bonded to the benzene ring. The α-position (carbon atom at the α-position) refers to the carbon atom to which the benzene ring is bonded, unless otherwise specified.
Examples of the substituent that substitutes the hydrogen atom at the α-position of the hydroxystyrene include the same as those exemplified as the substituent at the α-position in the above-mentioned α-substituted acrylic ester.

The term "structural unit derived from vinylbenzoic acid or a vinylbenzoic acid derivative" refers to a structural unit formed by cleavage of the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acid derivative.
The term "vinyl benzoic acid derivative" refers to a concept including vinyl benzoic acid in which the hydrogen atom at the α-position is replaced by other substituents such as an alkyl group or a halogenated alkyl group, as well as derivatives thereof. Examples of such derivatives include vinyl benzoic acid in which the hydrogen atom at the α-position may be replaced by a substituent, the hydrogen atom of the carboxyl group of the vinyl benzoic acid in which the hydrogen atom at the α-position may be replaced by a substituent, and ... a substituent other than a hydroxyl group or a carboxyl group is bonded to the benzene ring of the vinyl benzoic acid. The α-position (carbon atom at the α-position) refers to the carbon atom to which the benzene ring is bonded, unless otherwise specified.

The alkyl group as the substituent at the α-position is preferably a linear or branched alkyl group, and specific examples thereof include alkyl groups having 1 to 5 carbon atoms (such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group).
Specific examples of the halogenated alkyl group as the substituent at the α-position include groups in which some or all of the hydrogen atoms of the above-mentioned "alkyl group as the substituent at the α-position" are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferred.
Specific examples of the hydroxyalkyl group as the substituent at the α-position include the above-mentioned "alkyl group as the substituent at the α-position" in which some or all of the hydrogen atoms have been substituted with hydroxyl groups. The number of hydroxyl groups in the hydroxyalkyl group is preferably 1 to 5, and most preferably 1.

In this specification and claims, some structures represented by chemical formulas may have asymmetric carbons, and enantiomers or diastereomers may exist. In such cases, a single chemical formula represents all of the isomers. These isomers may be used alone or as a mixture.

(Resist Composition)
The resist composition according to the first aspect of the present invention generates an acid upon exposure and changes its solubility in a developer by the action of the acid, and contains a base component (A) (hereinafter also referred to as "component (A)") whose solubility in a developer changes by the action of the acid, and an ionic liquid (Z) (hereinafter also referred to as "component (Z)"). The solids concentration of the resist composition of this embodiment is 25 mass % or more.
When such a resist composition is used to form a resist film, a thick resist film (for example, a film thickness of 5 μm or more) can be formed.

When a resist film is formed using such a resist composition and selectively exposed to light, an acid is generated in the exposed areas of the resist film, and the solubility of component (A) in the developer changes due to the action of the acid, while the solubility of component (A) in the developer does not change in the unexposed areas of the resist film, resulting in a difference in solubility in the developer between the exposed and unexposed areas of the resist film. Therefore, when the resist film is developed, if the resist composition is a positive type, the exposed areas of the resist film are dissolved and removed to form a positive type resist pattern, and if the resist composition is a negative type, the unexposed areas of the resist film are dissolved and removed to form a negative type resist pattern.

In this specification, a resist composition in which an exposed portion of a resist film is dissolved and removed to form a positive resist pattern is referred to as a positive resist composition, and a resist composition in which an unexposed portion of a resist film is dissolved and removed to form a negative resist pattern is referred to as a negative resist composition. The resist composition of this embodiment may be a positive resist composition or a negative resist composition. The resist composition of this embodiment may be for an alkaline development process in which an alkaline developer is used for the development treatment when forming a resist pattern, or may be for a solvent development process in which a developer containing an organic solvent (organic developer) is used for the development treatment.

The resist composition of this embodiment has an acid generating ability to generate an acid upon exposure. The component (A) may generate an acid upon exposure, or an additive component that is formulated separately from the component (A) may generate an acid upon exposure.
Specifically, the resist composition of this embodiment may be (1) one that further contains an acid generator component (B) that generates an acid upon exposure (hereinafter referred to as “component (B)”); (2) one in which the component (A) is a component that generates an acid upon exposure; or (3) one in which the component (A) is a component that generates an acid upon exposure, and further contains a component (B).
That is, in the above cases (2) and (3), the component (A) is a "base component that generates an acid upon exposure and changes its solubility in a developer by the action of the acid". When the component (A) is a base component that generates an acid upon exposure and changes its solubility in a developer by the action of the acid, it is preferable that the component (A1) described below is a polymeric compound that generates an acid upon exposure and changes its solubility in a developer by the action of the acid. As such a polymeric compound, a resin having a structural unit that generates an acid upon exposure can be used. As the structural unit that generates an acid upon exposure, a known one can be used. Among them, the resist composition of this embodiment is preferably the above case (1).

<Component (A)>
In the resist composition of this embodiment, the component (A) preferably contains a resin component (A1) (hereinafter also referred to as "component (A1)") whose solubility in a developer changes under the action of an acid. By using the component (A1), the polarity of the base component changes before and after exposure, so that good development contrast can be obtained not only in an alkali development process but also in a solvent development process.
As the component (A), at least the component (A1) is used, and other polymeric compounds and/or low molecular weight compounds may be used in combination with the component (A1).

When an alkaline development process is applied, the base material component containing the component (A1) is poorly soluble in an alkaline developer before exposure, and when, for example, an acid is generated from the component (B) upon exposure, the polarity increases due to the action of the acid, and the solubility in an alkaline developer increases. Therefore, in forming a resist pattern, when a resist film obtained by applying the resist composition to a support is selectively exposed to light, the exposed parts of the resist film change from poorly soluble in an alkaline developer to soluble, while the unexposed parts of the resist film remain poorly soluble in alkaline developers, and a positive resist pattern is formed by alkaline development.

On the other hand, when a solvent development process is applied, the base material component containing the component (A1) is highly soluble in an organic developer before exposure, and when an acid is generated from the component (B) upon exposure, for example, the acid increases the polarity and reduces the solubility in an organic developer. Therefore, when the resist film obtained by applying the resist composition to a support is selectively exposed to light in the formation of a resist pattern, the exposed parts of the resist film change from soluble to poorly soluble in an organic developer, while the unexposed parts of the resist film remain soluble. Therefore, by developing with an organic developer, a contrast can be created between the exposed and unexposed parts, and a negative resist pattern is formed.

In the resist composition of this embodiment, the component (A) may be used alone or in combination of two or more types.

Regarding the Component (A1) The component (A1) is a resin component whose solubility in a developer changes due to the action of an acid.
The component (A1) preferably has a structural unit (a1) that contains an acid-decomposable group whose polarity increases when acted on by an acid.
The component (A1) may contain other structural units, in addition to the structural unit (a1), as necessary.

<Structural unit (a1)>
The structural unit (a1) is a structural unit that contains an acid-decomposable group whose polarity increases when acted upon by an acid.
The term "acid-decomposable group" refers to a group having acid decomposability in which at least a part of the bonds in the structure of the acid-decomposable group can be cleaved by the action of an acid.
Examples of acid-decomposable groups whose polarity increases under the action of an acid include groups that are decomposed by the action of an acid to generate a polar group.
Examples of the polar group include a carboxy group, a hydroxyl group, an amino group, a sulfo group (-SO ₃ H), etc. Among these, a polar group containing -OH in the structure (hereinafter sometimes referred to as an "OH-containing polar group") is preferred, a carboxy group or a hydroxyl group is more preferred, and a carboxy group is particularly preferred.
More specific examples of the acid-decomposable group include groups in which the polar group is protected with an acid-dissociable group (for example, a group in which the hydrogen atom of an OH-containing polar group is protected with an acid-dissociable group).

The term "acid dissociable group" as used herein refers to both (i) a group having acid dissociability in which the bond between the acid dissociable group and an atom adjacent to the acid dissociable group can be cleaved by the action of an acid, and (ii) a group in which a part of the bond is cleaved by the action of an acid and then a decarboxylation reaction occurs, thereby cleaving the bond between the acid dissociable group and an atom adjacent to the acid dissociable group.
The acid dissociable group constituting the acid decomposable group must be a group with lower polarity than the polar group generated by dissociation of the acid dissociable group, and thus, when the acid dissociable group is dissociated by the action of an acid, a polar group with higher polarity than the acid dissociable group is generated, and the polarity increases.As a result, the polarity of the entire (A1) component increases.By increasing the polarity, the solubility in the developer changes relatively, and when the developer is an alkaline developer, the solubility increases, and when the developer is an organic developer, the solubility decreases.

Examples of the acid-dissociable group include those that have been proposed as acid-dissociable groups in base resins for chemically amplified resist compositions.
Specific examples of the acid dissociable group that have been proposed for the base resin of the chemically amplified resist composition include the “acetal type acid dissociable group”, “tertiary alkyl ester type acid dissociable group”, and “tertiary alkyloxycarbonyl acid dissociable group”, which are explained below.

Acetal type acid dissociable group:
Among the polar groups, examples of the acid dissociable group that protects a carboxy group or a hydroxyl group include an acid dissociable group represented by the following general formula (a1-r-1) (hereinafter referred to as an "acetal-type acid dissociable group"). ) are some examples.

［式中、Ｒａ’^１、Ｒａ’^２は水素原子またはアルキル基である。Ｒａ’^３は炭化水素基であって、Ｒａ’^３は、Ｒａ’^１、Ｒａ’^２のいずれかと結合して環を形成してもよい。］

[In the formula, Ra' ¹ and Ra' ² are a hydrogen atom or an alkyl group. Ra' ³ is a hydrocarbon group, and Ra' ³ may be bonded to either Ra' ¹ or Ra' ² to form a ring.]

In formula (a1-r-1), at least one of ^Ra'1 and ^Ra'2 is preferably a hydrogen atom, and more preferably both are hydrogen atoms.
When ^Ra'1 or ^Ra'2 is an alkyl group, examples of the alkyl group include the same alkyl groups as those exemplified as the substituent that may be bonded to the carbon atom at the α-position in the description of the above α-substituted acrylic acid ester, and an alkyl group having 1 to 5 carbon atoms is preferred. Specifically, preferred examples are linear or branched alkyl groups. More specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group, and the like. A methyl group or an ethyl group is more preferred, and a methyl group is particularly preferred.

In formula (a1-r-1), the hydrocarbon group for ^Ra'3 includes a linear or branched alkyl group, or a cyclic hydrocarbon group.
The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably has 1 to 4 carbon atoms, and even more preferably has 1 or 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and more preferably has 3 to 5 carbon atoms. Specific examples include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group, and is preferably an isopropyl group.

When ^Ra'3 is a cyclic hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a polycyclic group or a monocyclic group.
The monocyclic aliphatic hydrocarbon group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.
As the aliphatic hydrocarbon group that is a polycyclic group, a group in which one hydrogen atom has been removed from a polycycloalkane is preferable, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

When the cyclic hydrocarbon group of ^Ra'3 is an aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.
The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, further preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms.
Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is replaced with a heteroatom. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring.
Specific examples of the aromatic hydrocarbon group in ^Ra'3 include a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl group or heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); and a group in which one hydrogen atom of the aromatic hydrocarbon ring or aromatic heterocycle has been substituted with an alkylene group (e.g., arylalkyl groups such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, etc.). The alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocycle preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably has 1 carbon atom.

The cyclic hydrocarbon group for Ra' ³ may have a substituent. Examples of the substituent include -R ^P1 , -R ^P2 -O-R ^P1 , -R ^P2 -CO-R ^P1 , -R ^P2 -CO-OR ^P1 , -R ^P2 -O-CO-R ^P1 , -R ^P2 -OH, -R ^P2 -CN or -R ^P2 -COOH (hereinafter these substituents are collectively referred to as "Ra ⁰⁵ ").
Here, R ^P1 is a monovalent linear saturated hydrocarbon group having 1 to 10 carbon atoms, a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms. R ^P2 is a single bond, a divalent linear saturated hydrocarbon group having 1 to 10 carbon atoms, a divalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms. However, some or all of the hydrogen atoms of the linear saturated hydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, and the aromatic hydrocarbon group of R ^P1 and R ^P2 may be substituted with fluorine atoms. The aliphatic cyclic hydrocarbon group may have one or more of the above-mentioned substituents alone, or may have one or more of each of the above-mentioned substituents.
Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.
Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo[3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.
Examples of the monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms include groups in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, biphenyl, fluorene, naphthalene, anthracene, or phenanthrene.

When ^Ra'3 is bonded to either ^Ra'1 or ^Ra'2 to form a ring, the cyclic group is preferably a 4- to 7-membered ring, more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group, a tetrahydrofuranyl group, etc.

Tertiary alkyl ester type acid-dissociable group:
Among the above polar groups, examples of the acid-dissociable group that protects the carboxy group include acid-dissociable groups represented by the following general formula (a1-r-2).
Among the acid-dissociable groups represented by the following formula (a1-r-2), those constituted by an alkyl group may be referred to as "tertiary alkyl ester-type acid-dissociable groups" hereinafter for the sake of convenience.

［式中、Ｒａ’^４～Ｒａ’^６はそれぞれ炭化水素基であって、Ｒａ’^５、Ｒａ’^６は互いに結合して環を形成してもよい。］

[In the formula, Ra' ⁴ to Ra' ⁶ are each a hydrocarbon group, and Ra' ⁵ and Ra' ⁶ may be bonded to each other to form a ring.]

Examples of the hydrocarbon group for ^Ra'4 include a linear or branched alkyl group, a linear or cyclic alkenyl group, or a cyclic hydrocarbon group.
Examples of the linear or branched alkyl group and cyclic hydrocarbon group (monocyclic aliphatic hydrocarbon group, polycyclic aliphatic hydrocarbon group, and aromatic hydrocarbon group) in ^Ra'4 are the same as those for ^Ra'3 .
The chain or cyclic alkenyl group for ^Ra'4 is preferably an alkenyl group having 2 to 10 carbon atoms.
Examples of the hydrocarbon group for ^Ra'5 and ^Ra'6 include the same as those for ^Ra'3 .

When ^Ra'5 and ^Ra'6 are bonded to each other to form a ring, suitable examples of such a ring include a group represented by the following general formula (a1-r2-1), a group represented by the following general formula (a1-r2-2), and a group represented by the following general formula (a1-r2-3).
On the other hand, when Ra' ⁴ to Ra' ⁶ are not bonded to one another and are independent hydrocarbon groups, suitable examples include groups represented by the following general formula (a1-r2-4).

［式（ａ１－ｒ２－１）中、Ｒａ’^１０は、炭素数１～１０のアルキル基、又は下記一般式（ａ１－ｒ２－ｒ１）で表される基を示す。Ｒａ’^１１はＲａ’^１０が結合した炭素原子と共に脂肪族環式基を形成する基を示す。式（ａ１－ｒ２－２）中、Ｙａは炭素原子である。Ｘａは、Ｙａと共に環状の炭化水素基を形成する基である。この環状の炭化水素基が有する水素原子の一部又は全部は置換されていてもよい。Ｒａ^０１～Ｒａ^０３は、それぞれ独立して、水素原子、炭素数１～１０の１価の鎖状飽和炭化水素基又は炭素数３～２０の１価の脂肪族環状飽和炭化水素基である。この鎖状飽和炭化水素基及び脂肪族環状飽和炭化水素基が有する水素原子の一部又は全部は置換されていてもよい。Ｒａ^０１～Ｒａ^０３の２つ以上が互いに結合して環状構造を形成していてもよい。式（ａ１－ｒ２－３）中、Ｙａａは炭素原子である。Ｘａａは、Ｙａａと共に脂肪族環式基を形成する基である。Ｒａ^０４は、置換基を有していてもよい芳香族炭化水素基である。式（ａ１－ｒ２－４）中、Ｒａ’^１２及びＲａ’^１３は、それぞれ独立に、炭素数１～１０の１価の鎖状飽和炭化水素基又は水素原子である。この鎖状飽和炭化水素基が有する水素原子の一部又は全部は置換されていてもよい。Ｒａ’^１４は、置換基を有していてもよい炭化水素基である。＊は結合手を示す。］

[In formula (a1-r2-1), Ra' ¹⁰ represents an alkyl group having 1 to 10 carbon atoms, or a group represented by the following general formula (a1-r2-r1). Ra' ¹¹ represents a group forming an aliphatic cyclic group together with the carbon atom to which Ra' ¹⁰ is bonded. In formula (a1-r2-2), Ya represents a carbon atom. Xa represents a group forming a cyclic hydrocarbon group together with Ya. Some or all of the hydrogen atoms in this cyclic hydrocarbon group may be substituted. Ra ⁰¹ to Ra ⁰³ are each independently a hydrogen atom, a monovalent linear saturated hydrocarbon group having 1 to 10 carbon atoms, or a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms. Some or all of the hydrogen atoms in this linear saturated hydrocarbon group and aliphatic cyclic saturated hydrocarbon group may be substituted. Two or more of Ra ⁰¹ to Ra ⁰³ may be bonded to each other to form a cyclic structure. In formula (a1-r2-3), Yaa is a carbon atom. Xaa is a group forming an aliphatic cyclic group together with Yaa. Ra ⁰⁴ is an aromatic hydrocarbon group which may have a substituent. In formula (a1-r2-4), Ra' ¹² and Ra' ¹³ are each independently a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom. Some or all of the hydrogen atoms in this chain saturated hydrocarbon group may be substituted. Ra' ¹⁴ is a hydrocarbon group which may have a substituent. * indicates a bond.]

［式中、Ｙａ^０は、第４級炭素原子である。Ｒａ^０３１、Ｒａ^０３２及びＲａ^０３３は、それぞれ独立に、置換基を有していてもよい炭化水素基である。但し、Ｒａ^０３１、Ｒａ^０３２及びＲａ^０３３のうちの１つ以上は、少なくとも一つの極性基を有する炭化水素基である。］

[In the formula, Ya ⁰ is a quaternary carbon atom. Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ are each independently a hydrocarbon group which may have a substituent. However, at least one of Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is a hydrocarbon group having at least one polar group.]

In the above formula (a1-r2-1), the alkyl group having 1 to 10 carbon atoms for ^Ra'10 is preferably the same as those exemplified as the linear or branched alkyl group for ^Ra'3 in formula (a1-r-1). ^Ra'10 is preferably an alkyl group having 1 to 5 carbon atoms.

In the above formula (a1-r2-r1), Ya ⁰ is a quaternary carbon atom, that is, there are four adjacent carbon atoms bonded to Ya ⁰ (carbon atom).

In the formula (a1-r2-r1), Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ each independently represent a hydrocarbon group which may have a substituent. The hydrocarbon group in Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ each independently includes a linear or branched alkyl group, a linear or cyclic alkenyl group, or a cyclic hydrocarbon group.

The linear alkyl group in Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group and the like. Of these, a methyl group, an ethyl group or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.
The branched alkyl group in Ra ⁰³¹ , Ra ⁰³² , and Ra ⁰³³ preferably has a carbon number of 3 to 10, and more preferably 3 to 5. Specific examples include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group, and is preferably an isopropyl group.
The chain or cyclic alkenyl group for Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is preferably an alkenyl group having 2 to 10 carbon atoms.

The cyclic hydrocarbon group for Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a polycyclic group or a monocyclic group.
The monocyclic aliphatic hydrocarbon group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.
As the aliphatic hydrocarbon group that is a polycyclic group, a group in which one hydrogen atom has been removed from a polycycloalkane is preferable, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group in Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is a hydrocarbon group having at least one aromatic ring. The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, further preferably 6 to 15, and particularly preferably 6 to 12. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene and phenanthrene; and aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring. Specific examples of the aromatic hydrocarbon group include a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl group or heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); a group in which one hydrogen atom of the aromatic hydrocarbon ring or aromatic heterocycle has been substituted with an alkylene group (e.g., arylalkyl groups such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, etc.). The number of carbon atoms in the alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocycle is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

When the hydrocarbon groups represented by the above Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ are substituted, examples of the substituent include a hydroxy group, a carboxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, etc.), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc.), an alkyloxycarbonyl group and the like.

Among the above, the optionally substituted hydrocarbon group in Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is preferably a linear or branched alkyl group which may have a substituent, more preferably a linear alkyl group which may have a substituent.

However, at least one of Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is a hydrocarbon group having at least a polar group.
The term "hydrocarbon group having a polar group" includes both a hydrocarbon group in which a methylene group (-CH ₂ -) constituting the hydrocarbon group is replaced with a polar group, and a hydrocarbon group in which at least one hydrogen atom constituting the hydrocarbon group is replaced with a polar group.
As such a "hydrocarbon group having a polar group", a functional group represented by the following general formula (a1-p1) is preferable.

［式中、Ｒａ^０７は、炭素数２～１２の２価の炭化水素基を表す。Ｒａ^０８は、ヘテロ原子を含む２価の連結基を表す。Ｒａ^０６は、炭素数１～１２の１価の炭化水素基を表す。ｎ_ｐ０は、１～６の整数である。］

[In the formula, Ra ⁰⁷ represents a divalent hydrocarbon group having 2 to 12 carbon atoms. Ra ⁰⁸ represents a divalent linking group containing a hetero atom. Ra ⁰⁶ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms. n _p0 is an integer of 1 to 6.]

In the above formula (a1-p1), Ra ⁰⁷ represents a divalent hydrocarbon group having 2 to 12 carbon atoms.
Ra ⁰⁷ has 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 2 carbon atoms.
The hydrocarbon group for Ra ⁰⁷ is preferably a chain or cyclic aliphatic hydrocarbon group, and more preferably a chain hydrocarbon group.
Examples of Ra ⁰⁷ include linear alkanediyl groups such as ethylene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, and dodecane-1,12-diyl; branched alkanediyl groups such as cyclobutane-1,3-diyl group, cyclopentane-1,3-diyl group, cyclohexane-1,4-diyl group, cyclooctane-1,5-diyl group, and the like; and polycyclic divalent alicyclic hydrocarbon groups such as norbornane-1,4-diyl group, norbornane-2,5-diyl group, adamantane-1,5-diyl group, and the like.
Among the above, an alkanediyl group is preferred, and a linear alkanediyl group is more preferred.

In the above formula (a1-p1), Ra ⁰⁸ represents a divalent linking group containing a hetero atom.
Examples of Ra ⁰⁸ include -O-, -C(=O)-O-, -C(=O)-, -O-C(=O)-O-, -C(=O)-NH-, -NH-, -NH-C(=NH)- (H may be substituted with a substituent such as an alkyl group or an acyl group), -S-, -S(=O) ₂ -, -S(=O) ₂ -O-, and the like.
Among these, from the viewpoint of solubility in a developer, -O-, -C(=O)-O-, -C(=O)- and -OC(=O)-O- are preferred, with -O- and -C(=O)- being particularly preferred.

In the above formula (a1-p1), Ra ⁰⁶ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms.
Ra ⁰⁶ has 1 to 12 carbon atoms, and from the viewpoint of solubility in a developer, preferably has 1 to 8 carbon atoms, more preferably has 1 to 5 carbon atoms, even more preferably has 1 to 3 carbon atoms, particularly preferably has 1 or 2 carbon atoms, and most preferably has 1 carbon atom.

The hydrocarbon group for Ra ⁰⁶ may be a chain hydrocarbon group, a cyclic hydrocarbon group, or a combination of a chain and a cyclic hydrocarbon group.
Examples of chain hydrocarbon groups include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, a 2-ethylhexyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, and an n-dodecyl group.

The cyclic hydrocarbon group may be an alicyclic hydrocarbon group or an aromatic hydrocarbon group.
The alicyclic hydrocarbon group may be either monocyclic or polycyclic, and examples of the monocyclic alicyclic hydrocarbon group include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl. Examples of the polycyclic alicyclic hydrocarbon group include decahydronaphthyl, adamantyl, 2-alkyladamantan-2-yl, 1-(adamantan-1-yl)alkane-1-yl, norbornyl, methylnorbornyl, and isobornyl.
Examples of aromatic hydrocarbon groups include a phenyl group, a naphthyl group, an anthryl group, a p-methylphenyl group, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, a biphenyl group, a phenanthryl group, a 2,6-diethylphenyl group, and a 2-methyl-6-ethylphenyl group.

From the viewpoint of solubility in a developer, Ra ⁰⁶ is preferably a chain hydrocarbon group, more preferably an alkyl group, and even more preferably a linear alkyl group.

In the formula (a1-p1), n _p0 represents an integer of 1 to 6, preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 1.

Specific examples of the hydrocarbon group having at least a polar group are shown below.
In the following formula, * represents a bond bonded to the quaternary carbon atom (Ya ⁰ ).

In the above formula (a1-r2-r1), the number of hydrocarbon groups having at least a polar group among Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ is one or more, but this may be appropriately determined in consideration of the solubility in a developer during resist pattern formation. For example, it is preferable that the number be one or two of Ra ⁰³¹ , Ra ⁰³² and Ra ⁰³³ , and particularly preferably one.

The hydrocarbon group having at least a polar group may have a substituent other than the polar group. Examples of the substituent include a halogen atom (such as a fluorine atom, a chlorine atom, or a bromine atom) and a halogenated alkyl group having 1 to 5 carbon atoms.

In formula (a1-r2-1), Ra' ¹¹ (the aliphatic cyclic group formed together with the carbon atom to which Ra' ¹⁰ is bonded) is preferably the same as the groups exemplified as the monocyclic or polycyclic aliphatic hydrocarbon group for Ra' ³ in formula (a1-r-1).

In formula (a1-r2-2), examples of the cyclic hydrocarbon group formed by Xa together with Ya include groups in which one or more hydrogen atoms have been further removed from the cyclic monovalent hydrocarbon group (aliphatic hydrocarbon group) in ^Ra'3 in formula (a1-r-1).
The cyclic hydrocarbon group formed by Xa together with Ya may have a substituent. Examples of the substituent include the same substituents as those which the cyclic hydrocarbon group in ^Ra'3 may have.
In formula (a1-r2-2), examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms for Ra ⁰¹ to Ra ⁰³ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.
Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms for Ra ⁰¹ to Ra ⁰³ include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo[3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.
From the viewpoint of ease of synthesis of the monomer compound from which the structural unit (a1) is derived, Ra ⁰¹ to Ra ⁰³ are preferably a hydrogen atom or a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, and of these, a hydrogen atom, a methyl group, or an ethyl group is more preferable, and a hydrogen atom is particularly preferable.

Examples of the substituent that the chain saturated hydrocarbon group or the alicyclic saturated hydrocarbon group represented by the above Ra ⁰¹ to Ra ⁰³ may have include the same groups as those represented by the above Ra ⁰⁵ .

Examples of groups containing a carbon-carbon double bond resulting from two or more of Ra ⁰¹ to Ra ⁰³ bonding together to form a cyclic structure include a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, a methylcyclohexenyl group, a cyclopentylidene ethenyl group, a cyclohexylidene ethenyl group, etc. Of these, from the viewpoint of ease of synthesis of the monomer compound from which the structural unit (a1) is derived, a cyclopentenyl group, a cyclohexenyl group, and a cyclopentylidene ethenyl group are preferred.

In formula (a1-r2-3), the aliphatic cyclic group formed by Xaa together with Yaa is preferably the same as those exemplified as the monocyclic or polycyclic aliphatic hydrocarbon group for ^Ra'3 in formula (a1-r-1).
In formula (a1-r2-3), examples of the aromatic hydrocarbon group for Ra ⁰⁴ include groups in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Among these, Ra ⁰⁴ is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene or phenanthrene, even more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from benzene or naphthalene, and most preferably a group in which one or more hydrogen atoms have been removed from benzene.

Examples of the substituent that Ra ⁰⁴ in formula (a1-r2-3) may have include a methyl group, an ethyl group, a propyl group, a hydroxyl group, a carboxyl group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, etc.), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc.), an alkyloxycarbonyl group, and the like.

In formula (a1-r2-4), Ra' ¹² and Ra' ¹³ are each independently a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom. Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms in Ra' ¹² and Ra' ¹³ include the same as the monovalent chain saturated hydrocarbon groups having 1 to 10 carbon atoms in the above Ra ⁰¹ to Ra ^03. Some or all of the hydrogen atoms in this chain saturated hydrocarbon group may be substituted.
Among them, Ra' ¹² and Ra' ¹³ are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.
When the chain saturated hydrocarbon groups represented by the above ^Ra'12 and ^Ra'13 are substituted, examples of the substituent include the same groups as those for the above ^Ra05 .

In formula (a1-r2-4), Ra' ¹⁴ is a hydrocarbon group which may have a substituent. Examples of the hydrocarbon group in Ra' ¹⁴ include a linear or branched alkyl group, and a cyclic hydrocarbon group.

The linear alkyl group for Ra' ¹⁴ preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Of these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group for Ra' ¹⁴ preferably has 3 to 10 carbon atoms, and more preferably has 3 to 5 carbon atoms. Specific examples include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group, and is preferably an isopropyl group.

When Ra' ¹⁴ is a cyclic hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a polycyclic group or a monocyclic group.
The monocyclic aliphatic hydrocarbon group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.
As the aliphatic hydrocarbon group that is a polycyclic group, a group in which one hydrogen atom has been removed from a polycycloalkane is preferable, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

Examples of the aromatic hydrocarbon group for Ra' ¹⁴ include the same as the aromatic hydrocarbon group for Ra ^04. Among them, Ra' ¹⁴ is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene or phenanthrene, still more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from naphthalene or anthracene, and most preferably a group in which one or more hydrogen atoms have been removed from naphthalene.
Examples of the substituent which ^Ra'14 may have include the same substituents as those which ^Ra04 may have.

When Ra' ¹⁴ in formula (a1-r2-4) is a naphthyl group, the position at which it bonds to the tertiary carbon atom in formula (a1-r2-4) may be either the 1st or 2nd position of the naphthyl group.
When Ra' ¹⁴ in formula (a1-r2-4) is an anthryl group, the position at which it bonds to the tertiary carbon atom in formula (a1-r2-4) may be any one of the 1-position, 2-position or 9-position of the anthryl group.

Specific examples of the group represented by formula (a1-r2-1) are given below.

Specific examples of the group represented by formula (a1-r2-2) are given below.

Specific examples of the group represented by formula (a1-r2-3) are given below.

Specific examples of the group represented by formula (a1-r2-4) are given below.

Tertiary alkyloxycarbonyl acid dissociating group:
Among the polar groups, examples of the acid dissociable group that protects the hydroxyl group include acid dissociable groups represented by the following general formula (a1-r-3) (hereinafter, for convenience, may be referred to as “tertiary alkyloxycarbonyl acid dissociable group”).

［式中、Ｒａ’^７～Ｒａ’^９はそれぞれアルキル基である。］

[In the formula, Ra' ⁷ to Ra' ⁹ each represent an alkyl group.]

In formula (a1-r-3), Ra' ⁷ to Ra' ⁹ are each preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms.
The total number of carbon atoms in each alkyl group is preferably 3 to 7, more preferably 3 to 5, and most preferably 3 or 4.

From the viewpoint of suppressing a decrease in light transmittance in a thick resist film, the structural unit (a1) is preferably one containing an acid dissociable group represented by the general formula (a1-r-2), and more preferably one containing an acid dissociable group represented by the general formula (a1-r2-4). In the general formula (a1-r2-4), Ra' ¹² and Ra' ¹³ are each independently preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. In the general formula (a1-r2-4), Ra' ¹⁴ is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

Examples of the structural unit (a1) include structural units derived from acrylic esters in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent, structural units derived from acrylamide, structural units in which at least some of the hydrogen atoms in the hydroxyl groups of a structural unit derived from hydroxystyrene or a hydroxystyrene derivative are protected with a substituent containing the acid-decomposable group, and structural units in which at least some of the hydrogen atoms in -C(=O)-OH of a structural unit derived from vinylbenzoic acid or a vinylbenzoic acid derivative are protected with a substituent containing the acid-decomposable group.

Of the above, the structural unit (a1) is preferably a structural unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent.
Preferred specific examples of the structural unit (a1) include structural units represented by general formula (a1-1) or (a1-2) shown below.

［式中、Ｒは、水素原子、炭素数１～５のアルキル基又は炭素数１～５のハロゲン化アルキル基である。Ｖａ^１は、エーテル結合を有していてもよい２価の炭化水素基である。ｎ_ａ１は、０～２の整数である。Ｒａ^１は、上記の一般式（ａ１－ｒ－１）又は（ａ１－ｒ－２）で表される酸解離性基である。Ｗａ^１はｎ_ａ２＋１価の炭化水素基であり、ｎ_ａ２は１～３の整数であり、Ｒａ^２は上記の一般式（ａ１－ｒ－１）又は（ａ１－ｒ－３）で表される酸解離性基である。］

[In the formula, R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ^{Va 1} is a divalent hydrocarbon group which may have an ether bond. _{n a1} is an integer of 0 to 2. Ra ¹ is an acid dissociable group represented by the above general formula (a1-r-1) or (a1-r-2). Wa ¹ is n _a2 +1 valent hydrocarbon group, n _a2 is an integer of 1 to 3, and Ra ² is an acid dissociable group represented by the above general formula (a1-r-1) or (a1-r-3).]

In the formula (a1-1), the alkyl group having 1 to 5 carbon atoms represented by R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. The halogenated alkyl group having 1 to 5 carbon atoms is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferred.
R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and from the viewpoint of industrial availability, a hydrogen atom or a methyl group is most preferred.

In the above formula (a1-1), the divalent hydrocarbon group for ^Va1 may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon group in ^Va1 may be saturated or unsaturated, and is usually preferably saturated.
More specifically, the aliphatic hydrocarbon group may be a straight-chain or branched-chain aliphatic hydrocarbon group, or an aliphatic hydrocarbon group containing a ring in the structure.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably has 1 to 6 carbon atoms, further preferably has 1 to 4 carbon atoms, and most preferably has 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight-chain alkylene group is preferable, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], a pentamethylene group [-(CH ₂ ) ₅ -], etc.
The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably has 3 to 6 carbon atoms, even more preferably has 3 or 4 carbon atoms, and most preferably has 3 carbon atoms.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C _{(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2- ; alkylethylene groups such as -CH ( CH3 ) CH2- ,} -CH( _{CH3 )} CH( _CH3 )-, -C _{( CH3} ) _{2CH2- ,} -CH( _{CH2CH3 ) CH2- , and -C} ( _CH2CH3 ) _{2 - CH2-} ; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , _-CH2CH ( _CH3 ) _CH2CH2- , etc.; and alkylalkylene groups such as alkyltetramethylene groups such as -CH( _CH3 ) _{CH2CH2CH2- , -CH2CH} (CH3) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

Examples of the aliphatic hydrocarbon group containing a ring in the structure include an alicyclic hydrocarbon group (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), a group in which an alicyclic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, a group in which an alicyclic hydrocarbon group is interposed in the middle of a linear or branched aliphatic hydrocarbon group, etc. Examples of the linear or branched aliphatic hydrocarbon group include the same as the linear aliphatic hydrocarbon group or the branched aliphatic hydrocarbon group.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be polycyclic or monocyclic. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon group in ^Va1 is a hydrocarbon group having an aromatic ring.
The aromatic hydrocarbon group preferably has a carbon number of 3 to 30, more preferably 5 to 30, even more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 12. However, this carbon number does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring contained in the aromatic hydrocarbon group include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom, etc. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the aromatic hydrocarbon ring (arylene group); a group in which one hydrogen atom of a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring (aryl group) has been substituted with an alkylene group (for example, a group in which one hydrogen atom has been further removed from the aryl group in an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The number of carbon atoms in the alkylene group (the alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

In the formula (a1-1), Ra ¹ is an acid-dissociable group represented by the formula (a1-r-1) or (a1-r-2).

In the formula (a1-1), n _a1 is an integer of 0 to 2. n _a1 is preferably 0 or 1, and more preferably 0.

In the formula (a1-2), the n _a2 +1 valent hydrocarbon group in Wa ¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group means a hydrocarbon group that does not have aromaticity, and may be saturated or unsaturated, and is usually preferably saturated. Examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, aliphatic hydrocarbon groups containing a ring in the structure, and groups that combine linear or branched aliphatic hydrocarbon groups with aliphatic hydrocarbon groups containing a ring in the structure.
The n _a2 +1 valency is preferably divalent to tetravalent, and more preferably divalent or trivalent.

In the formula (a1-2), ^Ra2 is an acid-dissociable group represented by the above general formula (a1-r-1) or (a1-r-3).

Specific examples of the structural unit represented by formula (a1-1) are shown below: In each of the following formulas, R ^α represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

Specific examples of the structural unit represented by formula (a1-2) are shown below.

The structural unit (a1) contained in the component (A1) may be of one type, or two or more types.
As the structural unit (a1), a structural unit represented by the above formula (a1-1) is more preferable, since it is easier to improve the characteristics (sensitivity, shape, etc.) in electron beam or EUV lithography.
Among these, as the structural unit (a1), it is particularly preferable that the structural unit (a1) includes a structural unit represented by general formula (a1-1-1) shown below.

［式中、Ｒａ^１”は、一般式（ａ１－ｒ２－１）、（ａ１－ｒ２－３）又は（ａ１－ｒ２－４）で表される酸解離性基である。］

[In the formula, Ra ¹ ″ is an acid-dissociable group represented by general formula (a1-r2-1), (a1-r2-3) or (a1-r2-4)]

In the formula (a1-1-1), R, ^Va1 and n _a1 are the same as R, ^Va1 and n _a1 in the formula (a1-1).
The acid dissociable group represented by general formula (a1-r2-1), (a1-r2-3) or (a1-r2-4) has been described above. From the viewpoint of maintaining the transparency of the thick resist film, Ra ¹ ″ is preferably an acid dissociable group represented by general formula (a1-r2-4). Preferred examples of Ra' ¹² _, Ra' ¹³ and Ra' ¹⁴ in general formula (a1-r2-4) are as described above.

The proportion of the structural unit (a1) in the component (A1) is preferably 5 to 80 mol %, more preferably 10 to 75 mol %, even more preferably 15 to 70 mol %, and particularly preferably 20 to 60 mol %, based on the total (100 mol %) of all structural units constituting the component (A1).
By ensuring that the proportion of the structural unit (a1) is at least as large as the lower limit of the aforementioned preferred range, lithography properties such as sensitivity, resolution, and roughness can be improved. On the other hand, when the proportion is at most the upper limit of the aforementioned preferred range, a balance with other structural units can be achieved, and various lithography properties become favorable.

Other structural units
The component (A1) may contain other structural units, in addition to the structural unit (a1) described above, as necessary.
Examples of other structural units include structural units (a2) containing a lactone-containing cyclic group, _{an -SO2-} containing cyclic group, or a carbonate-containing cyclic group; structural units (a3) containing a polar group-containing aliphatic hydrocarbon group; structural units (a4) containing an acid non-dissociable aliphatic cyclic group; structural units (a10) represented by the general formula (a10-1) described below; and structural units (st) derived from styrene or a derivative thereof.

Regarding the structural unit (a2):
The component (A1) may further contain, in addition to the structural unit (a1), a structural unit (a2) containing a lactone-containing cyclic group, an —SO ₂ —-containing cyclic group, or a carbonate-containing cyclic group (excluding those that correspond to the structural unit (a1)).
The lactone-containing cyclic group, -SO ₂ -containing cyclic group or carbonate-containing cyclic group of the structural unit (a2) is effective in improving the adhesion of the resist film to a substrate when the component (A1) is used to form a resist film. Furthermore, the presence of the structural unit (a2) provides effects such as appropriate adjustment of the acid diffusion length, improved adhesion of the resist film to a substrate, and appropriate adjustment of solubility during development, resulting in improved lithography properties.

A "lactone-containing cyclic group" refers to a cyclic group that contains a ring (lactone ring) that contains --O--C(=O)-- in its ring skeleton. The lactone ring is counted as the first ring, and when there is only a lactone ring, it is called a monocyclic group, and when there is further contained another ring structure, it is called a polycyclic group regardless of the structure. The lactone-containing cyclic group may be a monocyclic group or a polycyclic group.
The lactone-containing cyclic group in the structural unit (a2) is not particularly limited and any suitable group can be used. Specific examples include the groups represented by the following general formulae (a2-r-1) to (a2-r-7).

［式中、Ｒａ’^２１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、－ＣＯＯＲ”、－ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子、アルキル基、ラクトン含有環式基、カーボネート含有環式基、又は－ＳＯ_２－含有環式基であり；Ａ”は酸素原子（－Ｏ－）もしくは硫黄原子（－Ｓ－）を含んでいてもよい炭素数１～５のアルキレン基、酸素原子または硫黄原子であり、ｎ’は０～２の整数であり、ｍ’は０または１である。］

[In the formula, Ra' ²¹ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, -COOR", -OC(=O)R", a hydroxyalkyl group or a cyano group; R" is a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group or an -SO ₂ - containing cyclic group; A" is an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom (-O-) or a sulfur atom (-S-), an oxygen atom or a sulfur atom, n' is an integer of 0 to 2, and m' is 0 or 1.]

In the general formulae (a2-r-1) to (a2-r-7), the alkyl group in ^Ra'21 is preferably an alkyl group having 1 to 6 carbon atoms. The alkyl group is preferably linear or branched. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a hexyl group. Of these, a methyl group or an ethyl group is preferred, and a methyl group is particularly preferred.
The alkoxy group in Ra' ²¹ is preferably an alkoxy group having 1 to 6 carbon atoms. The alkoxy group is preferably linear or branched. Specific examples include groups in which the alkyl groups listed above as the alkyl groups in Ra' ²¹ are linked to an oxygen atom (-O-).
Examples of the halogen atom in ^Ra'21 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.
The halogenated alkyl group in Ra' ²¹ may be a group in which some or all of the hydrogen atoms in the alkyl group in Ra' ²¹ have been substituted with the halogen atoms. As the halogenated alkyl group, a fluorinated alkyl group is preferable, and a perfluoroalkyl group is particularly preferable.

In —COOR″ and —OC(═O)R″ in Ra′ ²¹ , R″ is either a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or an —SO ₂ —-containing cyclic group.
The alkyl group for R″ may be linear, branched, or cyclic, and preferably has 1 to 15 carbon atoms.
When R″ is a linear or branched alkyl group, it preferably has 1 to 10 carbon atoms, more preferably has 1 to 5 carbon atoms, and is particularly preferably a methyl group or an ethyl group.
When R" is a cyclic alkyl group, it preferably has 3 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane which may or may not be substituted with a fluorine atom or a fluorinated alkyl group; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as a bicycloalkane, tricycloalkane, or tetracycloalkane. More specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.
Examples of the lactone-containing cyclic group for R″ include the same groups as those represented by the general formulae (a2-r-1) to (a2-r-7).
The carbonate-containing cyclic group for R″ is the same as the carbonate-containing cyclic group described later, and specific examples thereof include groups represented by general formulas (ax3-r-1) to (ax3-r-3).
The —SO ₂ — containing cyclic group for R″ is the same as the —SO ₂ — containing cyclic group described later, and specific examples include the groups represented by the general formulae (a5-r-1) to (a5-r-4).
The hydroxyalkyl group in Ra' ²¹ preferably has 1 to 6 carbon atoms, and specific examples include the alkyl group in Ra' ²¹ in which at least one hydrogen atom has been substituted with a hydroxyl group.

In the general formulae (a2-r-2), (a2-r-3) and (a2-r-5), the alkylene group having 1 to 5 carbon atoms for A" is preferably a straight-chain or branched-chain alkylene group, such as a methylene group, an ethylene group, an n-propylene group or an isopropylene group. When the alkylene group contains an oxygen atom or a sulfur atom, specific examples thereof include groups in which -O- or -S- is present at the terminal or between the carbon atoms of the alkylene group, such as O-CH ₂ -, -CH ₂ -O-CH ₂ -, -S-CH ₂ - and -CH ₂ -S-CH ₂ -. A" is preferably an alkylene group having 1 to 5 carbon atoms or -O-, more preferably an alkylene group having 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups represented by general formulas (a2-r-1) to (a2-r-7) are listed below.

The term "-SO ₂ -containing cyclic group" refers to a cyclic group containing a ring containing -SO ₂ - in its ring skeleton, and specifically, it is a cyclic group in which the sulfur atom (S) in -SO ₂ - forms part of the ring skeleton of the cyclic group. The ring containing -SO ₂ - in the ring skeleton is counted as the first ring, and if there is only this ring, it is called a monocyclic group, and if there is further ring structure, it is called a polycyclic group regardless of the structure. The -SO ₂ -containing cyclic group may be a monocyclic group or a polycyclic group.
The —SO ₂ —-containing cyclic group is particularly preferably a cyclic group containing —O—SO ₂ — in its ring skeleton, that is, a cyclic group containing a sultone ring in which —O—S— in —O—SO ₂ — forms part of the ring skeleton.
More specific examples of the —SO ₂ —-containing cyclic group include groups represented by the following general formulae (a5-r-1) to (a5-r-4).

［式中、Ｒａ’^５１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、－ＣＯＯＲ”、－ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子、アルキル基、ラクトン含有環式基、カーボネート含有環式基、又は－ＳＯ_２－含有環式基であり；Ａ”は酸素原子もしくは硫黄原子を含んでいてもよい炭素数１～５のアルキレン基、酸素原子または硫黄原子であり、ｎ’は０～２の整数である。］

[In the formula, Ra' ⁵¹ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, -COOR", -OC(=O)R", a hydroxyalkyl group or a cyano group; R" is a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group or an -SO ₂ - containing cyclic group; A" is an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom, an oxygen atom or a sulfur atom, and n' is an integer of 0 to 2.]

In the general formulae (a5-r-1) and (a5-r-2), A" is the same as A" in the general formulae (a2-r-2), (a2-r-3) and (a2-r-5).
Examples of the alkyl group, alkoxy group, halogen atom, halogenated alkyl group, -COOR", -OC(=O)R", and hydroxyalkyl group in Ra' ⁵¹ include the same as those mentioned in the description of Ra' ²¹ in the general formulae (a2-r-1) to (a2-r-7).
Specific examples of the groups represented by general formulae (a5-r-1) to (a5-r-4) are shown below, in which "Ac" represents an acetyl group.

A "carbonate-containing cyclic group" refers to a cyclic group that contains a ring (carbonate ring) that contains --O--C(=O)--O- in its ring skeleton. The carbonate ring is counted as the first ring, and when there is only a carbonate ring, it is called a monocyclic group, and when there is further contained another ring structure, it is called a polycyclic group regardless of the structure. The carbonate-containing cyclic group may be a monocyclic group or a polycyclic group.
The carbonate ring-containing cyclic group is not particularly limited and any one can be used. Specific examples include groups represented by the following general formulae (ax3-r-1) to (ax3-r-3).

［式中、Ｒａ’^ｘ３１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、－ＣＯＯＲ”、－ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子、アルキル基、ラクトン含有環式基、カーボネート含有環式基、又は－ＳＯ_２－含有環式基であり；Ａ”は酸素原子もしくは硫黄原子を含んでいてもよい炭素数１～５のアルキレン基、酸素原子または硫黄原子であり、ｐ’は０～３の整数であり、ｑ’は０または１である。］

[In the formula, Ra' ^x31 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, -COOR", -OC(=O)R", a hydroxyalkyl group or a cyano group; R" represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group or an -SO ₂ - containing cyclic group; A" represents an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom, an oxygen atom or a sulfur atom, p' represents an integer of 0 to 3, and q' represents 0 or 1.]

In the general formulae (ax3-r-2) to (ax3-r-3), A" is the same as A" in the general formulae (a2-r-2), (a2-r-3) and (a2-r-5).
Examples of the alkyl group, alkoxy group, halogen atom, halogenated alkyl group, -COOR", -OC(=O)R", and hydroxyalkyl group in Ra' ³¹ include the same as those mentioned in the description of Ra' ²¹ in the general formulae (a2-r-1) to (a2-r-7).
Specific examples of the groups represented by the general formulae (ax3-r-1) to (ax3-r-3) are shown below.

Of the various possibilities, the structural unit (a2) is preferably a structural unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent.
The structural unit (a2) is preferably a structural unit represented by general formula (a2-1) shown below.

［式中、Ｒは水素原子、炭素数１～５のアルキル基又は炭素数１～５のハロゲン化アルキル基である。Ｙａ^２１は単結合または２価の連結基である。Ｌａ^２１は－Ｏ－、－ＣＯＯ－、－ＣＯＮ（Ｒ’）－、－ＯＣＯ－、－ＣＯＮＨＣＯ－又は－ＣＯＮＨＣＳ－であり、Ｒ’は水素原子またはメチル基を示す。ただしＬａ^２１が－Ｏ－の場合、Ｙａ^２１は－ＣＯ－にはならない。Ｒａ^２１はラクトン含有環式基、カーボネート含有環式基、又は－ＳＯ_２－含有環式基である。］

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ^{Ya 21} represents a single bond or a divalent linking group. La ²¹ represents -O-, -COO-, -CON(R')-, -OCO-, -CONHCO-, or -CONHCS-, and R' represents a hydrogen atom or a methyl group. However, when La ²¹ is -O-, Ya ²¹ does not represent -CO-. Ra ²¹ represents a lactone-containing cyclic group, a carbonate-containing cyclic group, or an -SO ₂ -containing cyclic group.]

In the formula (a2-1), R is the same as defined above. R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and is particularly preferably a hydrogen atom or a methyl group from the viewpoint of industrial availability.

In the formula (a2-1), the divalent linking group for Ya ²¹ is not particularly limited, but suitable examples include a divalent hydrocarbon group which may have a substituent, and a divalent linking group containing a hetero atom.

Optionally substituted divalent hydrocarbon group:
When Ya ²¹ is a divalent hydrocarbon group which may have a substituent, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group in Ya ²¹ The aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.
Examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, and aliphatic hydrocarbon groups containing a ring in the structure.

...Straight-chain or branched-chain aliphatic hydrocarbon group The straight-chain aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight-chain alkylene group is preferable, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], a pentamethylene group [-(CH ₂ ) ₅ -], etc.
The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably has 3 to 6 carbon atoms, even more preferably has 3 or 4 carbon atoms, and most preferably has 3 carbon atoms.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C _{(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2- ; alkylethylene groups such as -CH ( CH3 ) CH2- ,} -CH( _{CH3 )} CH( _CH3 )-, -C _{( CH3} ) _{2CH2- ,} -CH( _{CH2CH3 ) CH2- , and -C} ( _CH2CH3 ) _{2 - CH2-} ; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , _-CH2CH ( _CH3 ) _CH2CH2- , etc.; and alkylalkylene groups such as alkyltetramethylene groups such as -CH( _CH3 ) _{CH2CH2CH2- , -CH2CH} (CH3) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The linear or branched aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms and substituted with a fluorine atom, and a carbonyl group.

... Aliphatic hydrocarbon groups containing a ring in the structure Examples of the aliphatic hydrocarbon groups containing a ring in the structure include cyclic aliphatic hydrocarbon groups (groups in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring) which may contain a substituent containing a heteroatom in the ring structure, groups in which the cyclic aliphatic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, groups in which the cyclic aliphatic hydrocarbon group is interposed in the middle of a linear or branched aliphatic hydrocarbon group, etc. Examples of the linear or branched aliphatic hydrocarbon group include the same as those described above.
The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The cyclic aliphatic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have a substituent, such as an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, or a carbonyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and further preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.
Examples of the halogenated alkyl group as the substituent include the alkyl groups in which some or all of the hydrogen atoms of the alkyl groups are substituted with the halogen atoms.
In the cyclic aliphatic hydrocarbon group, some of the carbon atoms constituting the ring structure may be substituted with a substituent containing a hetero atom. Preferred examples of the substituent containing a hetero atom include -O-, -C(=O)-O-, -S-, -S(=O) ₂ - and -S(=O) ₂ -O-.

Aromatic Hydrocarbon Group in Ya ²¹ The aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.
The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, still more preferably 6 to 15, and particularly preferably 6 to 12. However, the number of carbon atoms does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is replaced with a heteroatom. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring.
Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the aromatic hydrocarbon ring or aromatic heterocycle (arylene group or heteroarylene group); a group in which two hydrogen atoms have been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); a group in which one hydrogen atom of a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl group or heteroaryl group) has been substituted with an alkylene group (e.g., a group in which one hydrogen atom has been further removed from the aryl group in an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The number of carbon atoms in the alkylene group bonded to the aryl group or heteroaryl group is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

The aromatic hydrocarbon group may have a hydrogen atom substituted with a substituent. For example, a hydrogen atom bonded to an aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
Examples of the alkoxy group, halogen atom and halogenated alkyl group as the substituent include those exemplified as the substituent substituting a hydrogen atom of the cyclic aliphatic hydrocarbon group.

Divalent linking groups containing heteroatoms:
When Ya ²¹ is a divalent linking group containing a hetero atom, preferred examples of the linking group include -O-, -C(=O)-O-, -O-C(=O)-, -C(=O)-, -O-C(=O)-O-, -C(=O)-NH-, -NH-, -NH-C(=NH)- (H may be substituted by a substituent such as an alkyl group or an acyl group), -S-, -S(=O) ₂ -, -S(=O) ₂ -O-, and the general formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(=O)-O-, -C(=O)-O-Y ²¹ -, -[Y ²¹ -C(=O)-O] _{m "} -Y ²² -, -Y ²¹ -O-C(=O)-Y ²² - or a group represented by -Y ²¹ -S(═O) ₂ -O-Y ²² - [wherein Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent, O is an oxygen atom, and m″ is an integer of 0 to 3].
When the divalent linking group containing a hetero atom is -C(=O)-NH-, -C(=O)-NH-C(=O)-, -NH-, or -NH-C(=NH)-, the H may be substituted with a substituent such as an alkyl group, an acyl group, etc. The substituent (alkyl group, acyl group, etc.) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
In the general formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(═O)-O-, -C(═O)-O-Y ²¹ -, -[Y ²¹ -C(═O)-O] _m" -Y ²² -, -Y ²¹ -O-C(═O)-Y ²² - or -Y ²¹ -S(═O) ₂ -O-Y ²² -, Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include the same as those (divalent hydrocarbon group which may have a substituent) listed above in the description of the divalent linking group for Ya ²¹ .
Y ²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or ethylene group.
Y ²² is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.
In the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, m" is an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 1. That is, as the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, a group represented by the formula -Y ²¹ -C(═O)-O-Y ²² - is particularly preferred. Of these, a group represented by the formula -(CH ₂ ) _a' -C(═O)-O-(CH ₂ ) _b' - is preferred. In the formula, a' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1. b' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1.

Among the above, Ya ²¹ is preferably a single bond, an ester bond [-C(=O)-O-], an ether bond (-O-), a linear or branched alkylene group, or a combination thereof.

In the above formula (a2-1), Ra ²¹ represents a lactone-containing cyclic group, an —SO ₂ —-containing cyclic group, or a carbonate-containing cyclic group.
Suitable examples of the lactone-containing cyclic group, the —SO ₂ —-containing cyclic group, and the carbonate-containing cyclic group for Ra ²¹ include the groups represented by the above-mentioned general formulae (a2-r-1) to (a2-r-7), (a5-r-1) to (a5-r-4), and (ax3-r-1) to (ax3-r-3).
Among them, lactone-containing cyclic groups or -SO ₂ -containing cyclic groups are preferred, and the groups represented by the above general formulae (a2-r-1), (a2-r-2), (a2-r-6) and (a5-r-1) are more preferred. Specifically, any of the groups represented by the above chemical formulae (r-lc-1-1) to (r-lc-1-7), (r-lc-2-1) to (r-lc-2-18), (r-lc-6-1), (r-sl-1-1) and (r-sl-1-18) are more preferred.

The structural unit (a2) contained in the component (A1) may be of one type, or two or more types.
When the component (A1) contains the structural unit (a2), the proportion of the structural unit (a2) relative to the total (100 mol%) of all structural units constituting the component (A1) is preferably 5 to 60 mol%, more preferably 10 to 60 mol%, even more preferably 20 to 55 mol%, and particularly preferably 30 to 50 mol%.
When the proportion of the structural unit (a2) is at least as large as the preferable lower limit, the effects achieved by including the structural unit (a2) can be fully obtained due to the effects described above. When the proportion of the structural unit (a2) is no more than the upper limit, a balance with other structural units can be achieved, and various lithography properties become favorable.

Regarding the structural unit (a3):
In addition to the structural unit (a1), the component (A1) may further include a structural unit (a3) (excluding those corresponding to the structural unit (a1) or the structural unit (a2)) that includes a polar group-containing aliphatic hydrocarbon group. When the component (A1) includes the structural unit (a3), the hydrophilicity of the component (A) is increased, which contributes to improving the resolution. In addition, the acid diffusion length can be appropriately adjusted.

Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which some of the hydrogen atoms of an alkyl group are substituted with fluorine atoms, with a hydroxyl group being particularly preferred.
Examples of the aliphatic hydrocarbon group include linear or branched hydrocarbon groups having 1 to 10 carbon atoms (preferably alkylene groups) and cyclic aliphatic hydrocarbon groups (cyclic groups). The cyclic group may be a monocyclic group or a polycyclic group, and can be appropriately selected from the multitude of groups proposed for use in resins for ArF excimer laser resist compositions.

When the cyclic group is a monocyclic group, it is more preferable that the number of carbon atoms is 3 to 10. Among them, structural units derived from acrylic esters containing an aliphatic monocyclic group containing a hydroxyl group, a cyano group, a carboxy group, or a hydroxyalkyl group in which some of the hydrogen atoms of the alkyl group are substituted with fluorine atoms are more preferable. Examples of the monocyclic group include groups in which two or more hydrogen atoms have been removed from a monocycloalkane. Specific examples include groups in which two or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane, cyclohexane, and cyclooctane. Among these monocyclic groups, groups in which two or more hydrogen atoms have been removed from cyclopentane and groups in which two or more hydrogen atoms have been removed from cyclohexane are industrially preferable.

When the cyclic group is a polycyclic group, the number of carbon atoms in the polycyclic group is more preferably 7 to 30. Among them, structural units derived from acrylic esters containing an aliphatic polycyclic group containing a hydroxyl group, a cyano group, a carboxy group, or a hydroxyalkyl group in which some of the hydrogen atoms of the alkyl group are substituted with fluorine atoms are more preferred. Examples of the polycyclic group include groups in which two or more hydrogen atoms have been removed from bicycloalkanes, tricycloalkanes, tetracycloalkanes, etc. Specific examples include groups in which two or more hydrogen atoms have been removed from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among these polycyclic groups, groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane are industrially preferred.

There are no particular limitations on the structural unit (a3), and any structural unit can be used as long as it contains a polar group-containing aliphatic hydrocarbon group.
The structural unit (a3) is preferably a structural unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent, and which contains a polar group-containing aliphatic hydrocarbon group.
When the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a straight-chain or branched-chain hydrocarbon group having 1 to 10 carbon atoms, the structural unit (a3) is preferably a structural unit derived from a hydroxyethyl ester of acrylic acid.
Furthermore, when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a polycyclic group, preferred examples of the structural unit (a3) include structural units represented by the following formulas (a3-1), (a3-2), and (a3-3); when the hydrocarbon group is a monocyclic group, preferred examples of the structural unit (a3) include structural units represented by formula (a3-4).

［式中、Ｒは前記と同じであり、ｊは１～３の整数であり、ｋは１～３の整数であり、ｔ’は１～３の整数であり、ｌは０～５の整数であり、ｓは１～３の整数である。］

[In the formula, R is the same as above, j is an integer of 1 to 3, k is an integer of 1 to 3, t' is an integer of 1 to 3, l is an integer of 0 to 5, and s is an integer of 1 to 3.]

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that hydroxyl groups are bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that hydroxyl groups are bonded to the 3rd position of the adamantyl group.
It is preferable that j is 1, and it is particularly preferable that the hydroxyl group is bonded to the 3-position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t' is preferably 1. l is preferably 1. s is preferably 1. In these, a 2-norbornyl group or a 3-norbornyl group is preferably bonded to the end of the carboxyl group of the acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5- or 6-position of the norbornyl group.

In formula (a3-4), t' is preferably 1 or 2. l is preferably 0 or 1. s is preferably 1. The fluorinated alkyl alcohol is preferably bonded to the 3- or 5-position of the cyclohexyl group.

The structural unit (a3) contained in the component (A1) may be of one type, or two or more types.
When the component (A1) contains the structural unit (a3), the proportion of the structural unit (a3) is preferably 1 to 30 mol %, more preferably 2 to 25 mol %, and even more preferably 5 to 20 mol %, based on the total (100 mol %) of all structural units constituting the component (A1).
By ensuring that the proportion of the structural unit (a3) is at least as great as the preferred lower limit, the effects achieved by including the structural unit (a3) can be fully obtained due to the effects described above. By ensuring that the proportion of the structural unit (a3) is at most the preferred upper limit, a balance with other structural units can be achieved, and various lithography properties become favorable.

Regarding the structural unit (a4):
The component (A1) may further contain, in addition to the structural unit (a1), a structural unit (a4) that contains an acid non-dissociable aliphatic cyclic group.
By including the structural unit (a4) in the component (A1), the dry etching resistance of the formed resist pattern is improved. In addition, the hydrophobicity of the component (A) is enhanced. Improved hydrophobicity contributes to improvements in the resolution, resist pattern shape, etc., particularly in the case of a solvent development process.
The “acid non-dissociable cyclic group” within the structural unit (a4) is a cyclic group that, when acid is generated in the resist composition upon exposure (for example, when acid is generated from a structural unit that generates acid upon exposure or from the component (B)), does not dissociate even when acted upon by the acid, and remains as such within the structural unit.

The structural unit (a4) is preferably, for example, a structural unit derived from an acrylate ester that contains an acid non-dissociable aliphatic cyclic group. As the cyclic group, many of those conventionally known to be used as resin components in resist compositions for use with ArF excimer lasers, KrF excimer lasers (preferably KrF excimer lasers), and the like can be used.
The cyclic group is preferably at least one selected from a tricyclodecyl group, an adamantyl group, a tetracyclododecyl group, an isobornyl group, and a norbornyl group, in view of industrial availability, etc. These polycyclic groups may have a linear or branched alkyl group having 1 to 5 carbon atoms as a substituent.
Specific examples of the structural unit (a4) include structural units represented by general formulas (a4-1) to (a4-7) shown below.

［式中、Ｒ^αは前記と同じである。］

[In the formula, R ^α is the same as above.]

The structural unit (a4) contained in the component (A1) may be of one type, or two or more types.
When the component (A1) contains the structural unit (a4), the proportion of the structural unit (a4) is preferably 1 to 40 mol %, and more preferably 5 to 20 mol %, based on the total (100 mol %) of all structural units constituting the component (A1).
By ensuring that the proportion of the structural unit (a4) is at least as large as the preferred lower limit, the effects of including the structural unit (a4) can be fully obtained, while by ensuring that the proportion is no more than the preferred upper limit, it becomes easier to achieve a balance with other structural units.

Regarding the structural unit (a10):
The structural unit (a10) is a structural unit represented by general formula (a10-1) shown below.

［式中、Ｒは、水素原子、炭素数１～５のアルキル基又は炭素数１～５のハロゲン化アルキル基である。Ｙａ^ｘ１は、単結合又は２価の連結基である。Ｗａ^ｘ１は、（ｎ_ａｘ１＋１）価の芳香族炭化水素基である。ｎ_ａｘ１は、１以上の整数である。］

[In the formula, R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ^{Ya x1} is a single bond or a divalent linking group. ^{Wa x1} is an aromatic hydrocarbon group having a valence of (n _ax1 +1). n _ax1 is an integer of 1 or more.]

In the above formula (a10-1), R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.
The alkyl group having 1 to 5 carbon atoms for R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.
The halogenated alkyl group having 1 to 5 carbon atoms for R is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms have been substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferred.
R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and from the viewpoint of industrial availability, is more preferably a hydrogen atom, a methyl group, or a trifluoromethyl group, is further preferably a hydrogen atom or a methyl group, and is particularly preferably a methyl group.

In the above formula (a10-1), Ya ^x1 represents a single bond or a divalent linking group.
In the above chemical formula, the divalent linking group for Ya ^x1 is not particularly limited, but suitable examples include a divalent hydrocarbon group which may have a substituent, and a divalent linking group containing a hetero atom.

Optionally substituted divalent hydrocarbon group:
When Ya ^x1 is a divalent hydrocarbon group which may have a substituent, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group in Ya ^x1 The aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.
Examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, and aliphatic hydrocarbon groups containing a ring in the structure.

...Straight-chain or branched-chain aliphatic hydrocarbon group The straight-chain aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, even more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight-chain alkylene group is preferable, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], a pentamethylene group [-(CH ₂ ) ₅ -], etc.
The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably has 3 to 6 carbon atoms, even more preferably has 3 or 4 carbon atoms, and most preferably has 3 carbon atoms.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C _{(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2- ; alkylethylene groups such as -CH ( CH3 ) CH2- ,} -CH( _{CH3 )} CH( _CH3 )-, -C _{( CH3} ) _{2CH2- ,} -CH( _{CH2CH3 ) CH2- , and -C} ( _CH2CH3 ) _{2 - CH2-} ; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , _-CH2CH ( _CH3 ) _CH2CH2- , etc.; and alkylalkylene groups such as alkyltetramethylene groups such as -CH( _CH3 ) _{CH2CH2CH2- , -CH2CH} (CH3) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The linear or branched aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms and substituted with a fluorine atom, and a carbonyl group.

... Aliphatic hydrocarbon groups containing a ring in the structure Examples of the aliphatic hydrocarbon groups containing a ring in the structure include cyclic aliphatic hydrocarbon groups (groups in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring) which may contain a substituent containing a heteroatom in the ring structure, groups in which the cyclic aliphatic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, groups in which the cyclic aliphatic hydrocarbon group is interposed in the middle of a linear or branched aliphatic hydrocarbon group, etc. Examples of the linear or branched aliphatic hydrocarbon group include the same as those described above.
The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The cyclic aliphatic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have a substituent, such as an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, or a carbonyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and further preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.
Examples of the halogenated alkyl group as the substituent include the alkyl groups in which some or all of the hydrogen atoms of the alkyl groups are substituted with the halogen atoms.
In the cyclic aliphatic hydrocarbon group, some of the carbon atoms constituting the ring structure may be substituted with a substituent containing a hetero atom. Preferred examples of the substituent containing a hetero atom include -O-, -C(=O)-O-, -S-, -S(=O) ₂ - and -S(=O) ₂ -O-.

Aromatic Hydrocarbon Group in Ya ^x1 The aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.
The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, still more preferably 6 to 15, and particularly preferably 6 to 12. However, the number of carbon atoms does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is replaced with a heteroatom. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring.
Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the aromatic hydrocarbon ring or aromatic heterocycle (arylene group or heteroarylene group); a group in which two hydrogen atoms have been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); a group in which one hydrogen atom of a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (aryl group or heteroaryl group) has been substituted with an alkylene group (e.g., a group in which one hydrogen atom has been further removed from the aryl group in an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The number of carbon atoms in the alkylene group bonded to the aryl group or heteroaryl group is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

The aromatic hydrocarbon group may have a hydrogen atom substituted with a substituent. For example, a hydrogen atom bonded to an aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
Examples of the alkoxy group, halogen atom and halogenated alkyl group as the substituent include those exemplified as the substituent substituting a hydrogen atom of the cyclic aliphatic hydrocarbon group.

Divalent linking groups containing heteroatoms:
When Ya ^x1 is a divalent linking group containing a hetero atom, preferred examples of the linking group include -O-, -C(=O)-O-, -O-C(=O)-, -C(=O)-, -O-C(=O)-O-, -C(=O)-NH-, -NH-, -NH-C(=NH)- (H may be substituted by a substituent such as an alkyl group or an acyl group), -S-, -S(=O) ₂ -, -S(=O) ₂ -O-, the general formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(=O)-O-, -C(=O)-O-Y ²¹ -, -[Y ²¹ -C(=O)-O] _{m "} -Y ²² -, -Y ²¹ -O-C(=O)-Y ²² - or a group represented by -Y ²¹ -S(═O) ₂ -O-Y ²² - [wherein Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent, O is an oxygen atom, and m″ is an integer of 0 to 3].
When the divalent linking group containing a hetero atom is -C(=O)-NH-, -C(=O)-NH-C(=O)-, -NH-, or -NH-C(=NH)-, the H may be substituted with a substituent such as an alkyl group, acyl, etc. The substituent (alkyl group, acyl group, etc.) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
In the general formula -Y ²¹ -O-Y ²² -, -Y ²¹ -O-, -Y ²¹ -C(=O)-O-, -C(=O)-O-Y ²¹ -, -[Y ²¹ -C(=O)-O] _m" -Y ²² -, -Y ²¹ -O-C(=O)-Y ²² - or -Y ²¹ -S(=O) ₂ -O-Y ²² -, Y ²¹ and Y ²² each independently represent a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include the same as those (divalent hydrocarbon group which may have a substituent) listed in the description of the divalent linking group for Ya ^x1 above.
Y ²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or ethylene group.
Y ²² is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.
In the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, m" is an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 1. That is, as the group represented by the formula -[Y ²¹ -C(═O)-O] _m" -Y ²² -, a group represented by the formula -Y ²¹ -C(═O)-O-Y ²² - is particularly preferred. Of these, a group represented by the formula -(CH ₂ ) _a' -C(═O)-O-(CH ₂ ) _b' - is preferred. In the formula, a' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1. b' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1.

Among the above, Ya ^x1 is preferably a single bond, an ester bond [-C(=O)-O-, -O-C(=O)-], an ether bond (-O-), a linear or branched alkylene group, or a combination thereof, more preferably a single bond or an ester bond [-C(=O)-O-, -O-C(=O)-], and still more preferably a single bond.

In the above formula (a10-1), Wa ^x1 is an aromatic hydrocarbon group having a valence of (n _ax1 +1).
The aromatic hydrocarbon group in Wa ^x1 may be a group in which (n _ax1 +1) hydrogen atoms have been removed from an aromatic ring. The aromatic ring here is not particularly limited as long as it is a cyclic conjugated system having 4n+2 π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, even more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom. Examples of heteroatoms in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocycle include a pyridine ring and a thiophene ring.
Further, examples of the aromatic hydrocarbon group in Wa ^x1 include groups in which (n _ax1 +1) hydrogen atoms have been removed from an aromatic compound containing two or more aromatic rings (such as biphenyl and fluorene).
Among the above, Wa ^x1 is preferably a group in which (n _ax1 +1) hydrogen atoms have been removed from benzene, naphthalene, anthracene or biphenyl, more preferably a group in which (n _ax1 +1) hydrogen atoms have been removed from benzene or naphthalene, and even more preferably a group in which (n _ax1 +1) hydrogen atoms have been removed from benzene.

The aromatic hydrocarbon group in Wa ^x1 may or may not have a substituent, but preferably does not have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, and a halogenated alkyl group. Examples of the alkyl group, alkoxy group, halogen atom, and halogenated alkyl group as the substituent include the same as those exemplified as the substituent of the cyclic aliphatic hydrocarbon group in Ya ^x1 . When Wa ^x1 is a group in which (n _ax1 +1) hydrogen atoms have been removed from an aromatic ring, the substituent is a group that replaces a hydrogen atom in the group in which (n _ax1 +1) hydrogen atoms have been removed from the aromatic ring. The substituent is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, more preferably a linear or branched alkyl group having 1 to 3 carbon atoms, still more preferably an ethyl group or a methyl group, and particularly preferably a methyl group.

In the formula (a10-1), n _ax1 is an integer of 1 or more, preferably an integer of 1 to 10, more preferably an integer of 1 to 5, still more preferably 1, 2 or 3, and particularly preferably 1 or 2. Of these, n _ax1 is preferably 1.

Specific examples of the structural unit (a10) represented by the aforementioned formula (a10-1) are shown below.
In each of the following formulas, R ^α represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The structural unit (a10) contained in the component (A1) may be of one type, or two or more types.
When the component (A1) contains the structural unit (a10), the proportion of the structural unit (a10) in the component (A1) is preferably 5 to 80 mol %, more preferably 5 to 75 mol %, and even more preferably 10 to 70 mol %, based on the total (100 mol %) of all structural units constituting the component (A1).
By ensuring that the proportion of the structural unit (a10) is at least as large as the lower limit of the above range, sensitivity can be further improved, whereas by ensuring that the proportion is at most the upper limit of the above range, it becomes easier to achieve a balance with other structural units.

Regarding the structural unit (st):
The structural unit (st) is a structural unit derived from styrene or a styrene derivative. A "structural unit derived from styrene" refers to a structural unit formed by cleavage of the ethylenic double bond of styrene. A "structural unit derived from a styrene derivative" refers to a structural unit formed by cleavage of the ethylenic double bond of a styrene derivative.

"Styrene derivative" refers to a compound in which at least some of the hydrogen atoms of styrene are replaced with a substituent. Examples of styrene derivatives include those in which the hydrogen atom at the α-position of styrene is replaced with a substituent, those in which one or more hydrogen atoms on the benzene ring of styrene are replaced with a substituent, and those in which the hydrogen atom at the α-position of styrene and one or more hydrogen atoms on the benzene ring are replaced with a substituent.

Examples of the substituent that substitutes the hydrogen atom at the α-position of styrene include an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.
The alkyl group having 1 to 5 carbon atoms is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.
The halogenated alkyl group having 1 to 5 carbon atoms is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
The substituent substituting the hydrogen atom at the α-position of styrene is preferably an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group having 1 to 3 carbon atoms, and from the viewpoint of industrial availability, a methyl group is further preferable.

Examples of the substituent that substitutes the hydrogen atom on the benzene ring of styrene include an alkyl group, an alkoxy group, a halogen atom, and a halogenated alkyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and further preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being preferred.
Examples of the halogenated alkyl group as the substituent include the alkyl groups in which some or all of the hydrogen atoms of the alkyl groups are substituted with the halogen atoms.
The substituent for substituting the hydrogen atom on the benzene ring of styrene is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

As the structural unit (st), a structural unit derived from styrene or a structural unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms is preferred, a structural unit derived from styrene or a structural unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with a methyl group is more preferred, and a structural unit derived from styrene is even more preferred.

The structural unit (st) contained in the component (A1) may be of one type, or two or more types.
When the component (A1) contains a structural unit (st), the proportion of the structural unit (st) is preferably 1 to 30 mol %, and more preferably 3 to 20 mol %, based on the total (100 mol %) of all structural units constituting the component (A1).

The component (A1) contained in the resist composition may use either a single type of compound, or a combination of two or more types of compounds.
In the resist composition of this embodiment, the component (A1) can be a polymeric compound that has a repeating structure of the structural unit (a1).
Preferred examples of the component (A1) include polymeric compounds having a repeating structure of the structural unit (a1) and other structural units. Examples of the other structural units include the structural unit (a10) or the structural unit (st).
In addition to the combination of the two structural units described above, the structural units described above may be combined as a third or more structural units according to the desired effect. Examples of combinations of three or more structural units include the combination of the structural unit (a1), the structural unit (a10), and the structural unit (st).
Preferred examples of the component (A1) include polymeric compounds having a repeating structure of the structural unit (a1) and the structural unit (a10); polymeric compounds having a repeating structure of the structural unit (a1) and the structural unit (st); and polymeric compounds having a repeating structure of the structural unit (a1), the structural unit (a10) and the structural unit (st).

The component (A1) can be produced by dissolving monomers from which each structural unit is derived in a polymerization solvent, and then adding a radical polymerization initiator such as azobisisobutyronitrile (AIBN) or dimethyl azobisisobutyrate (e.g., V-601), and polymerizing the resulting mixture.
Alternatively, the component (A1) can be produced by dissolving a monomer that derives the structural unit (a1) and, if necessary, a monomer that derives a structural unit other than the structural unit (a1) in a polymerization solvent, adding the above-mentioned radical polymerization initiator to the resulting solution to polymerize, and then carrying out a deprotection reaction.
During polymerization, a chain transfer agent such as HS-CH ₂ -CH ₂ -CH ₂ -C(CF ₃ ) ₂ -OH may be used in combination to introduce a -C(CF ₃ ) ₂ -OH group to the end. A copolymer having a hydroxyalkyl group in which some of the hydrogen atoms of the alkyl group are substituted with fluorine atoms in this way is effective in reducing development defects and LER (line edge roughness: non-uniform unevenness of the line sidewalls).

The weight average molecular weight (Mw) of the component (A1) (based on polystyrene equivalent by gel permeation chromatography (GPC)) is not particularly limited, but is preferably 1,000 to 50,000, more preferably 2,000 to 30,000, and even more preferably 3,000 to 20,000.
When the Mw of the component (A1) is no more than the preferred upper limit of this range, the compound has sufficient solubility in a resist solvent for use as a resist, and when it is no less than the preferred lower limit of this range, the compound has good dry etching resistance and good cross-sectional shape of the resist pattern.
The dispersity (Mw/Mn) of the component (A1) is not particularly limited, but is preferably from 1.0 to 4.0, more preferably from 1.0 to 3.0, and particularly preferably from 1.0 to 2.0, where Mn represents the number average molecular weight.

- Regarding base components other than component (A1) The resist composition of this embodiment may use, as the component (A), a base component other than the component (A1) whose solubility in a developer changes due to the action of an acid. The base component other than the component (A1) is not particularly limited and may be arbitrarily selected from a large number of base components conventionally known for use in chemically amplified resist compositions, and may be a single polymeric compound or a low molecular compound, or a combination of two or more polymeric compounds or low molecular compounds.

The proportion of component (A1) in component (A) is preferably 25% by mass or more, more preferably 50% by mass or more, and even more preferably 75% by mass or more, and may be 100% by mass, based on the total mass of component (A). When the proportion is 25% by mass or more, a resist pattern having excellent lithography properties is easily formed.

In the resist composition of this embodiment, the content of component (A) is preferably 20% by mass or more relative to the total mass (100% by mass) of the resist composition. By making the content of component (A) 20% by mass or more, a thick resist film (for example, a film thickness of 5 μm or more) is easily formed. The upper limit of the content of component (A) is not particularly limited as long as it is a concentration that allows the formation of a resist film, but can be, for example, 50% by mass or less. The content of component (A) is preferably 20 to 50% by mass, more preferably 22 to 50% by mass, and even more preferably 25 to 50% by mass.

<Component (Z)>
The component (Z) is an ionic liquid.
An ionic liquid is a salt that exists in liquid form. An ionic liquid is a salt that is composed of a cation portion and an anion portion, and the electrostatic interaction between these ions is weak, making it difficult to crystallize. An ionic liquid has a melting point of 100°C or less, and further has the following characteristics 1) to 5).
Feature 1) Extremely low vapor pressure. Feature 2) Non-flammable over a wide temperature range. Feature 3) Remains liquid over a wide temperature range. Feature 4) Density can be changed significantly. Feature 5) Polarity can be controlled.
In this embodiment, the ionic liquid is preferably non-polymerizable.
The mass average molecular weight (Mw) of the ionic liquid is preferably 1,000 or less, more preferably 750 or less, and even more preferably 500 or less.

Cationic Moiety of Component (Z) The cationic moiety of component (Z) is not particularly limited, but because this makes it easier to obtain an improved phase separation performance effect, the dipole moment of the cationic moiety is preferably 3 debye or more, more preferably 3.2 to 15 debye, and even more preferably 3.4 to 12 debye.
The "dipole moment of the cationic moiety" refers to a parameter that quantitatively indicates the polarity (bias of charge) of the cationic moiety. 1 debye is defined as 1×10 ⁻¹⁸ esu·cm. In this specification, the dipole moment of the cationic moiety refers to a simulation value by CAChe. For example, it is measured by performing structural optimization using MM geometry (MM2) and PM3 geometry by CAChe Work System Pro Version 6.1.12.33.

Suitable examples of the cation having a dipole moment of 3 debye or more include an imidazolium ion, a pyrrolidinium ion, a piperidinium ion, an ammonium ion, a sulfonium ion, and a phosphonium ion.
That is, preferred (Z) components include, for example, imidazolium salts, pyrrolidinium salts, piperidinium salts, ammonium salts, sulfonium salts, and phosphonium salts. Among these salts, the cationic portion is preferably a cation having a substituent, since the phase separation performance is more easily improved. Among them, a cation containing an alkyl group having 1 or more carbon atoms which may have a substituent, or a cation containing a polar group is preferred. The alkyl group having 1 or more carbon atoms contained in the cation preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group. Examples of the substituent that the alkyl group having 2 or more carbon atoms may have include a hydroxy group, a vinyl group, and an allyl group. It is preferable that the alkyl group having 1 or more carbon atoms does not have a substituent. Examples of the polar group contained in the cation include a carboxy group, a hydroxy group, an amino group, and a sulfo group.
More preferred examples of the cation moiety of the component (Z) include cations represented by the following general formulas (z-ca-1) to (z-ca-5).

［式中、Ｒｚ^ｃ１～Ｒｚ^ｃ６は、それぞれ独立に、炭素数１～１２のアルキル基である。Ｒｚ^ｃ７～Ｒｚ^ｃ９は、それぞれ独立に、置換基を有してもよいアリール基である。Ｒｚ^ｃ１０～Ｒｚ^ｃ１３は、それぞれ独立に、炭素数１～２０の直鎖状のアルキル基である。］

[In the formula, Rz ^c1 to Rz ^c6 are each independently an alkyl group having 1 to 12 carbon atoms. Rz ^c7 to Rz ^c9 are each independently an aryl group which may have a substituent. Rz ^c10 to Rz ^c13 are each independently a linear alkyl group having 1 to 20 carbon atoms.]

In the formula (z-ca-1), Rz ^c1 and Rz ^c2 each independently represent an alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, and even more preferably a linear alkyl group having 1 to 6 carbon atoms. Of these, it is particularly preferable that Rz ^c1 is a methyl group or an ethyl group, and Rz ^c2 is a linear alkyl group having 1 to 4 carbon atoms.

In the formula (z-ca-2), Rz ^c3 and Rz ^c4 each independently represent an alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, and even more preferably a linear alkyl group having 1 to 6 carbon atoms. Of these, it is particularly preferable that Rz ^c3 is a methyl group or an ethyl group, and Rz ^c4 is a linear alkyl group having 1 to 4 carbon atoms.

In the formula (z-ca-3), Rz ^c5 and Rz ^c6 are each independently an alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, and even more preferably a linear alkyl group having 1 to 6 carbon atoms. Of these, it is particularly preferable that Rz ^c5 is a linear alkyl group having 1 to 6 carbon atoms, and Rz ^c6 is a linear alkyl group having 1 to 4 carbon atoms.

In the above formula (z-ca-4), Rz ^c7 to Rz ^c9 each independently represent an aryl group which may have a substituent, and are preferably a phenyl group or a naphthyl group, more preferably a phenyl group.
Examples of the substituent that the aryl group in Rz ^c7 to Rz ^c9 may have include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an aryl group, and groups represented by general formulas (ca-r-1) to (ca-r-7) described later, respectively.

In the formula (z-ca-5), Rz ^c10 to Rz ^c13 each independently represent a linear alkyl group having 1 to 20 carbon atoms, preferably a linear alkyl group having 3 to 18 carbon atoms, more preferably a linear alkyl group having 4 to 16 carbon atoms, and still more preferably a linear alkyl group having 5 to 15 carbon atoms.

Anion Moiety of Component (Z) The anion moiety of the component (Z) is not particularly limited, but examples thereof include anions represented by any of the following general formulas (z-an-1) to (z-an-5).

［式（ｚ－ａｎ－１）中、Ｒｚ^ａ１は置換基を有していてもよい芳香族炭化水素基、置換基を有していてもよい脂肪族環式基、又は置換基を有していてもよい鎖状の炭化水素基を表す。式（ｚ－ａｎ－２）中、Ｒｚ^ａ２はフッ素原子で置換されていてもよい炭素数１～５のアルキル基を表す。ｋは１～４の整数であり、ｌは０～３の整数であり、かつ、ｋ＋ｌ＝４である。式（ｚ－ａｎ－３）中、Ｒｚ^ａ３は、フッ素原子で置換されていてもよい炭素数１～５のアルキル基を表す。ｍは１～６の整数であり、ｎは０～５の整数であり、かつ、ｍ＋ｎ＝６である。］

[In formula (z-an-1), Rz ^a1 represents an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain-like hydrocarbon group which may have a substituent. In formula (z-an-2), Rz ^a2 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom. k is an integer of 1 to 4, l is an integer of 0 to 3, and k+l=4. In formula (z-an-3), Rz ^a3 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom. m is an integer of 1 to 6, n is an integer of 0 to 5, and m+n=6.]

［式（ｚ－ａｎ－４）中、Ｘ”は、少なくとも１つの水素原子がフッ素原子で置換された炭素数２～６のアルキレン基を表す。式（ｚ－ａｎ－５）中、Ｙ”及びＺ”は、それぞれ独立に、少なくとも１つの水素原子がフッ素原子で置換された炭素数１～１０のアルキル基を表す。］

[In formula (z-an-4), X" represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. In formula (z-an-5), Y" and Z" each independently represent an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.]

In the above formula (z-an-1), Rz ^a1 represents an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain hydrocarbon group which may have a substituent.

In the formula (z-an-1), when Rz ^a1 is an aromatic hydrocarbon group which may have a substituent, specific examples of the aromatic ring contained in R include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; aromatic heterocycles in which a portion of the carbon atoms constituting the aromatic hydrocarbon ring is substituted with a heteroatom; etc. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group include a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring (aryl group); a group in which one hydrogen atom of the aryl group has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group); and the like. The number of carbon atoms in the alkylene group (the alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.
The aromatic hydrocarbon group for R is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.

In the formula (z-an-1), when Rz ^a1 is an aliphatic cyclic group which may have a substituent, it may be polycyclic or monocyclic. As the monocyclic aliphatic cyclic group, a group in which one hydrogen atom has been removed from a monocycloalkane is preferable. As the monocycloalkane, one having 3 to 8 carbon atoms is preferable, and specific examples thereof include cyclopentane, cyclohexane, and cyclooctane. As the polycyclic aliphatic cyclic group, a group in which one hydrogen atom has been removed from a polycycloalkane is preferable, and as the polycycloalkane, one having 7 to 12 carbon atoms is preferable, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Among these, the aliphatic cyclic group is more preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.

In the formula (z-an-1), the chain-like hydrocarbon group of Rz ^a1 is preferably a chain-like alkyl group. The chain-like alkyl group preferably has 1 to 10 carbon atoms, and specific examples thereof include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups; and branched alkyl groups such as 1-methylethyl, 1-methylpropyl, 2-methylpropyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, and 4-methylpentyl groups. The chain-like alkyl group more preferably has 1 to 6 carbon atoms, and even more preferably has 1 to 3 carbon atoms. In addition, a linear alkyl group is preferable.

In the above formula (z-an-1), examples of the substituent that the aromatic hydrocarbon group, aliphatic cyclic group or chain hydrocarbon group of Rz ^a1 may have include a hydroxyl group, an alkyl group, a fluorine atom or a fluorinated alkyl group, and a triphenylphosphonium group.

In the above formula (z-an-1), Rz ^a1 is preferably a methyl group, a trifluoromethyl group, a p-tolyl group or a propyltriphenylphosphonium group.

In the above formula (z-an-2), Rz ^a2 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom.
k is an integer of 1 to 4, preferably an integer of 3 to 4, and most preferably 4.
l is an integer of 0 to 3, preferably an integer of 0 to 2, and most preferably 0. When l is 2 or more, multiple Rz ^a2 may be the same or different from each other, but are preferably the same as each other.

In the above formula (z-an-3), Rz ^a3 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom.
m is an integer of 1 to 6, preferably an integer of 3 to 6, and most preferably 6.
n is an integer of 0 to 5, preferably an integer of 0 to 3, and most preferably 0. When n is 2 or more, multiple Rz ^a3 may be the same or different from each other, but are preferably the same from each other.

In the formula (z-an-4), X" represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. The alkylene group here may be linear or branched, and has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and most preferably 3 carbon atoms.

In the formula (z-an-5), Y" and Z" each independently represent an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom. The alkyl group here may be linear or branched, and has 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms, and more preferably 1 to 3 carbon atoms. Of these, it is particularly preferable that both Y" and Z" in (z-an-5) are trifluoromethyl groups.
The number of carbon atoms in the alkylene group of X" or the number of carbon atoms in each of the alkyl groups of Y" and Z" is preferably as small as possible within the above carbon number range, for reasons such as good solubility in organic solvent components.

In addition, in the alkylene group of X" or each of the alkyl groups of Y" and Z", the more hydrogen atoms are replaced with fluorine atoms, the more preferable for reasons such as increased acid strength. The fluorination rate of the alkylene group or alkyl group is preferably 70 to 100%, more preferably 90 to 100%, and most preferably a perfluoroalkylene group or perfluoroalkyl group in which all hydrogen atoms are replaced with fluorine atoms.

As the anion moiety of the (Z) component, among the anion moieties represented by any of the above formulae (z-an-1) to (z-an-5), the anion moiety represented by the general formula (z-an-1), (z-an-2), (z-an-3) or (z-an-5) is preferred.

Among these, the (Z) component is preferably a compound represented by any one of the following general formulas (z-1) to (z-5).

［式中、Ｒｚ^ｃ１～Ｒｚ^ｃ６は、それぞれ独立に、炭素数１～１２のアルキル基である。Ｘｚ１^－～Ｘｚ５^－は、それぞれ独立に、前記一般式（ｚ－ａｎ－１）～（ｚ－ａｎ－５）のいずれかで表されるアニオンである。］

[In the formula, Rz ^c1 to Rz ^c6 each independently represent an alkyl group having 1 to 12 carbon atoms. Xz1 ^- to Xz5 ^- each independently represent an anion represented by any one of the general formulae (z-an-1) to (z-an-5) above.]

In the formulas (z-1) to (z-3), Rz ^c1 to Rz ^c6 are the same as Rz ^c1 to Rz ^c6 in the formulas (z-ca-1) to (z-ca-3).
In the formula (z-1), ^Xz1- is preferably an anion represented by the formula (z-an-5).
In the formula (z-2), ^Xz2- is preferably an anion represented by the formula (z-an-5).
In the formula (z-3), ^Xz3- is preferably an anion represented by the formula (z-an-2).
In the formula (z-4), ^Xz4- is preferably an anion represented by the formula (z-an-5).
In the formula (z-5), ^Xz5- is preferably an anion represented by the formula (z-an-5).

Specific examples of compound (IL) are given below, but are not limited to these.

In the resist composition of this embodiment, the component (Z) may use either a single type, or a combination of two or more types.
In the resist composition of this embodiment, the content of the component (Z) relative to 100 parts by mass of the component (A) is preferably more than 0 and less than 25 parts by mass, more preferably 0.1 to 20 parts by mass, even more preferably 0.5 to 15 parts by mass, and particularly preferably 3 to 12 parts by mass.
By adjusting the content of the (Z) component to at least the lower limit of the above range, it is possible to increase the sensitivity and also to suppress the occurrence of cracks during the formation of a resist pattern, whereas by adjusting the content of the (Z) component to at most the upper limit of the above range, it is possible to obtain a resist pattern with a good shape.

<Other ingredients>
The resist composition of this embodiment may further contain other components in addition to the above-mentioned components (A) and (Z). Examples of other components include the following components (B), (D), (E), (F), and (S).

<Acid generator component (B)>
The resist composition of this embodiment may further contain, in addition to the components (A) and (Z), an acid generator component (B) (hereafter referred to as “component (B)”) that generates acid upon exposure.
There are no particular limitations on the component (B), and any of the acid generators that have been proposed so far for use in chemically amplified resist compositions can be used.
Examples of such acid generators include onium salt-based acid generators such as iodonium salts and sulfonium salts, oxime sulfonate-based acid generators, diazomethane-based acid generators such as bisalkyl- or bisarylsulfonyl diazomethanes and poly(bissulfonyl) diazomethanes, nitrobenzylsulfonate-based acid generators, iminosulfonate-based acid generators, and disulfone-based acid generators.
The component (B) preferably contains a compound (B1) consisting of an onium salt (hereinafter referred to as "component (B1)").

Regarding the component (B1): Examples of the component (B1) include a compound represented by the following general formula (b-1) (hereinafter also referred to as "component (b-1)"), a compound represented by general formula (b-2) (hereinafter also referred to as "component (b-2)"), or a compound represented by general formula (b-3) (hereinafter also referred to as "component (b-3)").

［式中、Ｒ^１０１及びＲ^１０４～Ｒ^１０８は、それぞれ独立に、置換基を有していてもよい環式基、置換基を有していてもよい鎖状のアルキル基、又は置換基を有していてもよい鎖状のアルケニル基である。Ｒ^１０４とＲ^１０５とは相互に結合して環構造を形成していてもよい。Ｒ^１０２は、炭素数１～５のフッ素化アルキル基又はフッ素原子である。Ｙ^１０１は、酸素原子を含む２価の連結基又は単結合である。Ｖ^１０１～Ｖ^１０３は、それぞれ独立に、単結合、アルキレン基又はフッ素化アルキレン基である。Ｌ^１０１～Ｌ^１０２は、それぞれ独立に、単結合又は酸素原子である。Ｌ^１０３～Ｌ^１０５は、それぞれ独立に、単結合、－ＣＯ－又は－ＳＯ_２－である。ｍは１以上の整数であって、Ｍ’^ｍ＋はｍ価のオニウムカチオンである。］

[In the formula, R ¹⁰¹ and R ¹⁰⁴ to R ¹⁰⁸ are each independently a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent. R ¹⁰⁴ and R ¹⁰⁵ may be bonded to each other to form a ring structure. R ¹⁰² is a fluorinated alkyl group having 1 to 5 carbon atoms or a fluorine atom. Y ¹⁰¹ is a divalent linking group containing an oxygen atom or a single bond. ^{V 101} to V ¹⁰³ are each independently a single bond, an alkylene group, or a fluorinated alkylene group. L ¹⁰¹ to L ¹⁰² are each independently a single bond or an oxygen atom. L ¹⁰³ to L ¹⁰⁵ are each independently a single bond, -CO-, or -SO ₂ -. m is an integer of 1 or more, and M' ^m+ is an m-valent onium cation.]

{anion portion}
Anion in Component (b-1) In formula (b-1), R ¹⁰¹ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent.

Optionally substituted cyclic group:
The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group means a hydrocarbon group that does not have aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.

The aromatic hydrocarbon group for R ¹⁰¹ is a hydrocarbon group having an aromatic ring. The number of carbon atoms in the aromatic hydrocarbon group is preferably 3 to 30, more preferably 5 to 30, even more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 10. However, the number of carbon atoms does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring contained in the aromatic hydrocarbon group in R ¹⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, and aromatic heterocycles in which a part of the carbon atoms constituting these aromatic rings are substituted with heteroatoms, etc. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group for R ¹⁰¹ include a group in which one hydrogen atom has been removed from the aromatic ring (aryl group: for example, a phenyl group, a naphthyl group, etc.), a group in which one hydrogen atom of the aromatic ring has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, a 2-naphthylethyl group, etc.). The number of carbon atoms in the alkylene group (the alkyl chain in the arylalkyl group) is preferably 1 to 4, more preferably 1 to 2, and particularly preferably 1.

The cyclic aliphatic hydrocarbon group for R ¹⁰¹ includes an aliphatic hydrocarbon group containing a ring in the structure.
Examples of the aliphatic hydrocarbon group containing a ring in its structure include alicyclic hydrocarbon groups (groups in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), groups in which an alicyclic hydrocarbon group is bonded to the end of a straight-chain or branched-chain aliphatic hydrocarbon group, and groups in which an alicyclic hydrocarbon group is present in the middle of a straight-chain or branched-chain aliphatic hydrocarbon group.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among them, the polycycloalkane is more preferably a polycycloalkane having a polycyclic skeleton of a bridged ring system such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a polycyclic skeleton of a condensed ring system such as a cyclic group having a steroid skeleton.

Among these, the cyclic aliphatic hydrocarbon group for R ¹⁰¹ is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has a carbon number of 1 to 10, more preferably 1 to 6, even more preferably 1 to 4, and most preferably 1 to 3. As the linear aliphatic hydrocarbon group, linear alkylene groups are preferable, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], a pentamethylene group [-(CH ₂ ) ₅ -], and the like.
The branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, even more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms. As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C _{(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2- ; alkylethylene groups such as -CH ( CH3 ) CH2- ,} -CH( _{CH3 )} CH( _CH3 )-, -C _{( CH3} ) _{2CH2- ,} -CH( _{CH2CH3 ) CH2- , and -C} ( _CH2CH3 ) _{2 - CH2-} ; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , _-CH2CH ( _CH3 ) _CH2CH2- , etc.; and alkylalkylene groups such as alkyltetramethylene groups such as -CH( _CH3 ) _{CH2CH2CH2- , -CH2CH} (CH3) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The cyclic hydrocarbon group in R ¹⁰¹ may contain a heteroatom, such as a heterocycle. Specific examples include the lactone-containing cyclic groups represented by the general formulae (a2-r-1) to (a2-r-7) above, the —SO ₂ —-containing cyclic groups represented by the general formulae (a5-r-1) to (a5-r-4) above, and the heterocyclic groups represented by the following chemical formulae (r-hr-1) to (r-hr-16).

Examples of the substituent in the cyclic group of R ¹⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitro group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group or a tert-butyl group.
The alkoxy group as a substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as a substituent include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom being preferred.
Examples of the halogenated alkyl group as a substituent include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, n-butyl, and tert-butyl groups, in which some or all of the hydrogen atoms have been substituted with the above-mentioned halogen atoms.
The carbonyl group as a substituent is a group that substitutes a methylene group (-CH ₂ -) that constitutes a cyclic hydrocarbon group.

A chain alkyl group which may have a substituent:
The chain alkyl group for R ¹⁰¹ may be either a straight chain or a branched chain.
The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decanyl group, an undecyl group, a dodecyl group, a tridecyl group, an isotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, and a docosyl group.
The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specific examples include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

A chain alkenyl group which may have a substituent:
The chain alkenyl group for R ¹⁰¹ may be either linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 5, even more preferably 2 to 4, and particularly preferably 3. Examples of linear alkenyl groups include vinyl groups, propenyl groups (allyl groups), and butynyl groups. Examples of branched alkenyl groups include 1-methylvinyl groups, 2-methylvinyl groups, 1-methylpropenyl groups, and 2-methylpropenyl groups.
Of the above chain alkenyl groups, linear alkenyl groups are preferred, vinyl groups and propenyl groups are more preferred, and vinyl groups are particularly preferred.

Examples of the substituent in the chain alkyl or alkenyl group of R ¹⁰¹ include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, and the cyclic groups in R ¹⁰¹ above.

Among the above, R ¹⁰¹ is preferably a cyclic group which may have a substituent, and more preferably a cyclic hydrocarbon group which may have a substituent. More specifically, preferred are a phenyl group, a naphthyl group, a group in which one or more hydrogen atoms have been removed from a polycycloalkane, a lactone-containing cyclic group represented by each of the general formulae (a2-r-1) to (a2-r-7), and an —SO ₂ —-containing cyclic group represented by each of the general formulae (a5-r-1) to (a5-r-4).

In formula (b-1), Y ¹⁰¹ is a single bond or a divalent linking group containing an oxygen atom.
When Y ¹⁰¹ is a divalent linking group containing an oxygen atom, Y ¹⁰¹ may contain an atom other than an oxygen atom. Examples of the atom other than an oxygen atom include a carbon atom, a hydrogen atom, a sulfur atom, and a nitrogen atom.
Examples of the divalent linking group containing an oxygen atom include non-hydrocarbon oxygen-atom-containing linking groups such as an oxygen atom (ether bond: -O-), an ester bond (-C(=O)-O-), an oxycarbonyl group (-O-C(=O)-), an amide bond (-C(=O)-NH-), a carbonyl group (-C(=O)-), and a carbonate bond (-O-C(=O)-O-); and combinations of such non-hydrocarbon oxygen-atom-containing linking groups with alkylene groups. This combination may further be linked to a sulfonyl group (-SO ₂ -). Examples of such divalent linking groups containing an oxygen atom include the linking groups represented by the following general formulae (y-al-1) to (y-al-7):

［式中、Ｖ’^１０１は単結合または炭素数１～５のアルキレン基であり、Ｖ’^１０２は炭素数１～３０の２価の飽和炭化水素基である。］

[In the formula, V' ¹⁰¹ is a single bond or an alkylene group having 1 to 5 carbon atoms, and V' ¹⁰² is a divalent saturated hydrocarbon group having 1 to 30 carbon atoms.]

The divalent saturated hydrocarbon group for V' ¹⁰² is preferably an alkylene group having 1 to 30 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, and even more preferably an alkylene group having 1 to 5 carbon atoms.

The alkylene group in ^V'101 and ^V'102 may be a straight-chain alkylene group or a branched-chain alkylene group, with a straight-chain alkylene group being preferred.
Specific examples of the alkylene group in V' ¹⁰¹ and V' ¹⁰² include a methylene group [-CH ₂ -]; alkylmethylene groups such as -CH(CH ₃ )-, -CH(CH ₂ CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CH ₃ )(CH ₂ CH ₃ )-, -C(CH ₃ )(CH ₂ CH ₂ CH ₃ )-, and -C(CH ₂ CH ₃ ) ₂ -; an ethylene group [-CH ₂ CH ₂ -]; alkylethylene groups such as -CH(CH ₃ )CH ₂ -, -CH(CH ₃ )CH(CH ₃ )-, -C(CH ₃ ) ₂ CH ₂ -, and -CH(CH ₂ CH ₃ )CH ₂ -; a trimethylene group (n-propylene group) [-CH ₂ CH _2CH2- ]; alkyl trimethylene groups such as _-CH ( _CH3 ) _CH2CH2- and _-CH2CH ( _{CH3 ) CH2-} ; tetramethylene group _{[ -CH2CH2CH2CH2- ]} ; alkyl tetramethylene groups _such as -CH _{( CH3 ) CH2CH2CH2- and -CH2CH ( CH3 ) CH2CH2-} ; _{pentamethylene} group [ _{-CH2CH2CH2CH2CH2CH2-} ] _.
In addition, some of the methylene groups in the alkylene group in ^V'101 or ^V'102 may be substituted with a divalent aliphatic cyclic group having 5 to 10 carbon atoms. The aliphatic cyclic group is preferably a divalent group obtained by further removing one hydrogen atom from the cyclic aliphatic hydrocarbon group (monocyclic aliphatic hydrocarbon group, polycyclic aliphatic hydrocarbon group) of ^Ra'3 in formula (a1-r-1), and more preferably a cyclohexylene group, a 1,5-adamantylene group or a 2,6-adamantylene group.

Y ¹⁰¹ is preferably a divalent linking group containing an ester bond or a divalent linking group containing an ether bond, and more preferably a linking group represented by each of the above formulas (y-al-1) to (y-al-5).

In formula (b-1), V ¹⁰¹ is a single bond, an alkylene group, or a fluorinated alkylene group. The alkylene group or fluorinated alkylene group in V ¹⁰¹ preferably has 1 to 4 carbon atoms. Examples of the fluorinated alkylene group in V ¹⁰¹ include groups in which some or all of the hydrogen atoms of the alkylene group in V ¹⁰¹ have been substituted with fluorine atoms. Of these, V ¹⁰¹ is preferably a single bond, or a fluorinated alkylene group having 1 to 4 carbon atoms.

In formula (b-1), R ¹⁰² is a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. R ¹⁰² is preferably a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, and more preferably a fluorine atom.

Specific examples of the anion moiety represented by formula (b-1) include, for example, when Y ¹⁰¹ is a single bond, fluorinated alkylsulfonate anions such as trifluoromethanesulfonate anion and perfluorobutanesulfonate anion; and, when Y ¹⁰¹ is a divalent linking group containing an oxygen atom, anions represented by any of the following formulas (an-1) to (an-3) are included.

［式中、Ｒ”^１０１は、置換基を有してもよい脂肪族環式基、上記の化学式（ｒ－ｈｒ－１）～（ｒ－ｈｒ－６）でそれぞれ表される１価の複素環式基、又は置換基を有してもよい鎖状のアルキル基である。Ｒ”^１０２は、置換基を有してもよい脂肪族環式基、前記一般式（ａ２－ｒ－１）、（ａ２－ｒ－３）～（ａ２－ｒ－７）でそれぞれ表されるラクトン含有環式基、又は前記一般式（ａ５－ｒ－１）～（ａ５－ｒ－４）でそれぞれ表される－ＳＯ_２－含有環式基である。Ｒ”^１０３は、置換基を有してもよい芳香族環式基、置換基を有してもよい脂肪族環式基、又は置換基を有してもよい鎖状のアルケニル基である。Ｖ”^１０１は、単結合、炭素数１～４のアルキレン基、又は炭素数１～４のフッ素化アルキレン基である。Ｒ^１０２は、フッ素原子又は炭素数１～５のフッ素化アルキル基である。ｖ”はそれぞれ独立に０～３の整数であり、ｑ”はそれぞれ独立に０～２０の整数であり、ｎ”は０または１である。］

[In the formula, R" ¹⁰¹ is an aliphatic cyclic group which may have a substituent, a monovalent heterocyclic group represented by each of the above chemical formulas (r-hr-1) to (r-hr-6), or a chain alkyl group which may have a substituent. R" ¹⁰² is an aliphatic cyclic group which may have a substituent, a lactone-containing cyclic group represented by each of the above general formulas (a2-r-1), (a2-r-3) to (a2-r-7), or an -SO ₂ - containing cyclic group represented by each of the above general formulas (a5-r-1) to (a5-r-4). R" ¹⁰³ is an aromatic cyclic group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain alkenyl group which may have a substituent. V" ¹⁰¹ is a single bond, an alkylene group having 1 to 4 carbon atoms, or a fluorinated alkylene group having 1 to 4 carbon atoms. R ¹⁰² is a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. Each v" is independently an integer of 0 to 3, each q" is independently an integer of 0 to 20, and n" is 0 or 1.

The aliphatic cyclic groups which may have a substituent of R" ¹⁰¹ , R" ¹⁰² and R" ¹⁰³ are preferably the groups exemplified as the cyclic aliphatic hydrocarbon group in R ¹⁰¹ in formula (b-1) above. Examples of the substituent include the same as the substituents which may substitute the cyclic aliphatic hydrocarbon group in R ¹⁰¹ in formula (b-1) above.

The aromatic cyclic group in R″ ¹⁰³ which may have a substituent is preferably a group exemplified as the aromatic hydrocarbon group in the cyclic hydrocarbon group in R ¹⁰¹ in the above formula (b-1). Examples of the substituent include the same as the substituent which may substitute the aromatic hydrocarbon group in R ¹⁰¹ in the above formula (b-1).

The chain alkyl group which may have a substituent in R″ ¹⁰¹ is preferably a group exemplified as the chain alkyl group in R ¹⁰¹ in the above formula (b-1).
The chain alkenyl group which may have a substituent in R″ ¹⁰³ is preferably a group exemplified as the chain alkenyl group in R ¹⁰¹ in the above formula (b-1).

Anion in Component (b-2) In formula (b-2), R ¹⁰⁴ and R ¹⁰⁵ each independently represent a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples of these include the same as R ¹⁰¹ in formula (b-1). However, R ¹⁰⁴ and R ¹⁰⁵ may be bonded to each other to form a ring.
R ¹⁰⁴ and R ¹⁰⁵ are preferably a chain alkyl group which may have a substituent, and more preferably a linear or branched alkyl group, or a linear or branched fluorinated alkyl group.
The number of carbon atoms in the chain-like alkyl group is preferably 1 to 10, more preferably 1 to 7, and even more preferably 1 to 3. The number of carbon atoms in the chain-like alkyl group of ^{R 104} and R ¹⁰⁵ is preferably as small as possible within the above-mentioned range of carbon numbers, for reasons such as good solubility in a resist solvent. In addition, in the chain-like alkyl group of R ¹⁰⁴ and R ¹⁰⁵ , the more hydrogen atoms substituted with fluorine atoms, the stronger the acid strength becomes, and the more the transparency to high-energy light and electron beams of 250 nm or less is improved, which is preferable. The ratio of fluorine atoms in the chain-like alkyl group, i.e., the fluorination rate, is preferably 70 to 100%, more preferably 90 to 100%, and most preferably a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms.
In formula (b-2), V ¹⁰² and V ¹⁰³ each independently represent a single bond, an alkylene group, or a fluorinated alkylene group, and examples of V ¹⁰¹ in formula (b-1) include the same as those described above.
In formula (b-2), L ¹⁰¹ and L ¹⁰² each independently represent a single bond or an oxygen atom.

Anion in Component (b-3) In formula (b-3), R to ^R each independently represent a cyclic group which may have a ^substituent , a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples of these include the same as R ¹⁰¹ in formula (b-1).
In formula (b-3), L ¹⁰³ to L ¹⁰⁵ each independently represent a single bond, —CO— or —SO ₂ —.

Among the above, the anion portion of component (B) is preferably the anion in component (b-1). Among these, a fluorinated alkylsulfonate anion or an anion represented by any of the above general formulas (an-1) to (an-3) is more preferred, and a fluorinated alkylsulfonate anion or an anion represented by any of general formulas (an-1) and (an-2) is even more preferred.

{Cation part}
In the above formulae (b-1), (b-2) and (b-3), ^M'm+ represents an m-valent onium cation, of which sulfonium cation and iodonium cation are preferred.
m is an integer of 1 or more.

Preferred cationic moieties (( ^M'm+ ) _1/m ) include organic cations represented by the following general formulas (ca-1) to (ca-4).

［式中、Ｒ^２０１～Ｒ^２０７、およびＲ^２１１～Ｒ^２１２は、それぞれ独立に置換基を有していてもよいアリール基、アルキル基またはアルケニル基を表す。Ｒ^２０１～Ｒ^２０３、Ｒ^２０６～Ｒ^２０７、Ｒ^２１１～Ｒ^２１２は、相互に結合して式中のイオウ原子と共に環を形成してもよい。Ｒ^２０８～Ｒ^２０９は、それぞれ独立に水素原子または炭素数１～５のアルキル基を表す。Ｒ^２１０は、置換基を有していてもよいアリール基、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、又は置換基を有していてもよい－ＳＯ_２－含有環式基である。Ｌ^２０１は、－Ｃ（＝Ｏ）－または－Ｃ（＝Ｏ）－Ｏ－を表す。Ｙ^２０１は、それぞれ独立に、アリーレン基、アルキレン基またはアルケニレン基を表す。ｘは１または２である。Ｗ^２０１は（ｘ＋１）価の連結基を表す。］

[In the formula, R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² each independently represent an aryl group, an alkyl group, or an alkenyl group which may have a substituent. R ²⁰¹ to R ²⁰³ , R ²⁰⁶ to R ²⁰⁷ , and R ²¹¹ to R ²¹² may be bonded to each other to form a ring together with the sulfur atom in the formula. R ²⁰⁸ to R ²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ²¹⁰ is an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an -SO ₂ - containing cyclic group which may have a substituent. L ²⁰¹ represents -C(=O)- or -C(=O)-O-. Y ²⁰¹ each independently represent an arylene group, an alkylene group, or an alkenylene group. x is 1 or 2. W ²⁰¹ represents a (x+1)-valent linking group.

In the above general formulae (ca-1) to (ca-4), the aryl group for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² can be an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferable.
The alkyl group for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² is preferably a chain or cyclic alkyl group having 1 to 30 carbon atoms.
The alkenyl group for R ²⁰¹ to R ²⁰⁷ and R ²¹¹ to R ²¹² preferably has 2 to 10 carbon atoms.
Examples of the substituent that R ²⁰¹ to R ²⁰⁷ and R ²¹⁰ to R ²¹² may have include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an aryl group, and groups represented by the following general formulas (ca-r-1) to (ca-r-7), respectively.

［式中、Ｒ’^２０１は、それぞれ独立に、水素原子、置換基を有してもよい環式基、置換基を有してもよい鎖状のアルキル基、又は置換基を有してもよい鎖状のアルケニル基である。］

[In the formula, ^R'201 each independently represents a hydrogen atom, a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent.]

Optionally substituted cyclic group:
The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group means a hydrocarbon group that does not have aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.

The aromatic hydrocarbon group in ^R'201 is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, even more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbon atoms. However, this carbon number does not include the number of carbon atoms in the substituent.
Specific examples of the aromatic ring contained in the aromatic hydrocarbon group in ^R'201 include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, and aromatic heterocycles in which some of the carbon atoms constituting these aromatic rings are substituted with heteroatoms. Examples of the heteroatom in the aromatic heterocycle include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group for ^R'201 include a group in which one hydrogen atom has been removed from the aromatic ring (aryl group: for example, a phenyl group, a naphthyl group, etc.), a group in which one hydrogen atom of the aromatic ring has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, a 2-naphthylethyl group, etc.). The alkylene group (the alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.

The cyclic aliphatic hydrocarbon group for ^R'201 includes an aliphatic hydrocarbon group containing a ring in the structure.
Examples of the aliphatic hydrocarbon group containing a ring in its structure include alicyclic hydrocarbon groups (groups in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), groups in which an alicyclic hydrocarbon group is bonded to the end of a straight-chain or branched-chain aliphatic hydrocarbon group, and groups in which an alicyclic hydrocarbon group is present in the middle of a straight-chain or branched-chain aliphatic hydrocarbon group.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing one or more hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among them, the polycycloalkane is more preferably a polycycloalkane having a polycyclic skeleton of a bridged ring system such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a polycyclic skeleton of a condensed ring system such as a cyclic group having a steroid skeleton.

Among these, the cyclic aliphatic hydrocarbon group for ^R'201 is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear or branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.
As the straight-chain aliphatic hydrocarbon group, a straight-chain alkylene group is preferable, and specific examples thereof include a methylene group [-CH ₂ -], an ethylene group [-(CH ₂ ) ₂ -], a trimethylene group [-(CH ₂ ) ₃ -], a tetramethylene group [-(CH ₂ ) ₄ -], a pentamethylene group [-(CH ₂ ) ₅ -], etc.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples thereof include alkylmethylene groups such as -CH( _CH3 )-, -CH( _CH2CH3 )-, -C( _CH3 ) _2- , -C _{(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, and -C(CH2CH3)2- ; alkylethylene groups such as -CH ( CH3 ) CH2- ,} -CH( _{CH3 )} CH( _CH3 )-, -C _{( CH3} ) _{2CH2- ,} -CH( _{CH2CH3 ) CH2- , and -C} ( _CH2CH3 ) _{2 - CH2-} ; alkyltrimethylene groups such as -CH( _CH3 ) _CH2CH2CH2- , _-CH2CH ( _CH3 ) _CH2CH2- , etc.; and alkylalkylene groups such as alkyltetramethylene groups such as -CH( _CH3 ) _{CH2CH2CH2- , -CH2CH} (CH3) _CH2CH2- , etc. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

Furthermore, the cyclic hydrocarbon group in ^R'201 may contain a heteroatom, such as a heterocycle. Specific examples include the lactone-containing cyclic groups represented by the general formulae (a2-r-1) to (a2-r-7) above, the -SO ₂ -containing cyclic groups represented by the general formulae (a5-r-1) to (a5-r-4) above, and the heterocyclic groups represented by the chemical formulae (r-hr-1) to (r-hr-16) above.

Examples of the substituent in the cyclic group of ^R'201 include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitro group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group or a tert-butyl group.
The alkoxy group as a substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.
Examples of the halogen atom as a substituent include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, with a fluorine atom being preferred.
Examples of halogenated alkyl groups as substituents include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, n-butyl and tert-butyl groups, in which some or all of the hydrogen atoms have been substituted with the above-mentioned halogen atoms.
The carbonyl group as a substituent is a group that substitutes a methylene group (-CH ₂ -) that constitutes a cyclic hydrocarbon group.

A chain alkyl group which may have a substituent:
The chain alkyl group of ^R'201 may be either linear or branched.
The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably has 1 to 15 carbon atoms, and most preferably has 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decanyl group, an undecyl group, a dodecyl group, a tridecyl group, an isotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, and a docosyl group.
The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably has 3 to 15 carbon atoms, and most preferably has 3 to 10 carbon atoms. Specific examples include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

A chain alkenyl group which may have a substituent:
The chain alkenyl group for ^R'201 may be either linear or branched, and preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, further preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Examples of linear alkenyl groups include vinyl groups, propenyl groups (allyl groups), and butynyl groups. Examples of branched alkenyl groups include 1-methylvinyl groups, 2-methylvinyl groups, 1-methylpropenyl groups, and 2-methylpropenyl groups.
Of the above chain alkenyl groups, linear alkenyl groups are preferred, vinyl groups and propenyl groups are more preferred, and vinyl groups are particularly preferred.

Examples of the substituent in the chain alkyl or alkenyl group of ^R'201 include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, and the cyclic groups in ^R'201 described above.

In addition to those mentioned above, the optionally substituted cyclic group, optionally substituted chain alkyl group, or optionally substituted chain alkenyl group for ^R'201 also includes the same as the acid dissociable group represented by formula (a1-r-2) above as the optionally substituted cyclic group or optionally substituted chain alkyl group.

Among them, ^R'201 is preferably a cyclic group which may have a substituent, and more preferably a cyclic hydrocarbon group which may have a substituent. More specifically, for example, a phenyl group, a naphthyl group, a group in which one or more hydrogen atoms have been removed from a polycycloalkane, a lactone-containing cyclic group represented by each of the general formulae (a2-r-1) to (a2-r-7), an -SO ₂ --containing cyclic group represented by each of the general formulae (a5-r-1) to (a5-r-4), etc. are preferred.

In the above general formulae (ca-1) to (ca-4), when R ²⁰¹ to R ²⁰³ , R ²⁰⁶ to R ²⁰⁷ , and R ²¹¹ to R ²¹² are bonded to each other to form a ring together with the sulfur atom in the formula, they may be bonded via a heteroatom such as a sulfur atom, an oxygen atom, or a nitrogen atom, or a functional group such as a carbonyl group, -SO-, -SO ₂ -, -SO ₃ -, -COO-, -CONH-, or -N(R _N )- (wherein R _N is an alkyl group having 1 to 5 carbon atoms). As for the ring formed, it is preferable that one ring containing the sulfur atom in the ring skeleton in the formula is a 3- to 10-membered ring including the sulfur atom, and particularly preferably a 5- to 7-membered ring. Specific examples of the ring formed include a thiophene ring, a thiazole ring, a benzothiophene ring, a thianthrene ring, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, a thianthrene ring, a phenoxathiin ring, a tetrahydrothiophenium ring, and a tetrahydrothiopyranium ring.

R ²⁰⁸ to R ²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and when they represent an alkyl group, they may be bonded to each other to form a ring.

R ²¹⁰ is an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an --SO ₂ -- containing cyclic group which may have a substituent.
The aryl group for R ²¹⁰ includes unsubstituted aryl groups having 6 to 20 carbon atoms, and is preferably a phenyl group or a naphthyl group.
The alkyl group for R ²¹⁰ is preferably a chain or cyclic alkyl group having 1 to 30 carbon atoms.
The alkenyl group for R ²¹⁰ preferably has 2 to 10 carbon atoms.
As the optionally substituted —SO ₂ — containing cyclic group for R ²¹⁰ , a “—SO ₂ — containing polycyclic group” is preferable, and a group represented by the above general formula (a5-r-1) is more preferable.

Each Y ²⁰¹ independently represents an arylene group, an alkylene group, or an alkenylene group.
Examples of the arylene group for Y ²⁰¹ include groups in which one hydrogen atom has been removed from the aryl groups exemplified as the aromatic hydrocarbon group for R ¹⁰¹ in the above formula (b-1).
Examples of the alkylene group and alkenylene group for Y ²⁰¹ include groups in which one hydrogen atom has been removed from the groups exemplified as the chain alkyl group and chain alkenyl group for R ¹⁰¹ in the above formula (b-1).

In the above formula (ca-4), x is 1 or 2.
W ²⁰¹ is a (x+1)-valent linking group, that is, a divalent or trivalent linking group.
The divalent linking group in W ²⁰¹ is preferably a divalent hydrocarbon group which may have a substituent, and examples thereof include the same divalent hydrocarbon groups which may have a substituent as Ya ²¹ in the above general formula (a2-1). The divalent linking group in W ²⁰¹ may be linear, branched, or cyclic, and is preferably cyclic. Among these, a group in which two carbonyl groups are combined at both ends of an arylene group is preferred. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferred.
Examples of the trivalent linking group in W ²⁰¹ include a group in which one hydrogen atom has been removed from the divalent linking group in W ²⁰¹ , a group in which the divalent linking group is further bonded to the divalent linking group, etc. As the trivalent linking group in ^{W 201} , a group in which two carbonyl groups are bonded to an arylene group is preferable.

Specific examples of suitable cations represented by the formula (ca-1) include the cations represented by the following chemical formulas (ca-1-1) to (ca-1-70).

［式中、ｇ１、ｇ２、ｇ３は繰返し数を示し、ｇ１は１～５の整数であり、ｇ２は０～２０の整数であり、ｇ３は０～２０の整数である。］

[In the formula, g1, g2, and g3 represent the number of repetitions, where g1 is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is an integer of 0 to 20.]

［式中、Ｒ”^２０１は水素原子又は置換基であって、該置換基としては前記Ｒ^２０１～Ｒ^２０７、およびＲ^２１０～Ｒ^２１２が有していてもよい置換基として挙げたものと同様である。］

[In the formula, R″ ²⁰¹ is a hydrogen atom or a substituent, and the substituent is the same as those exemplified as the substituent that may be possessed by the above-mentioned R ²⁰¹ to R ²⁰⁷ and R ²¹⁰ to R ^212. ]

Specific examples of suitable cations represented by the formula (ca-2) include diphenyliodonium cation, bis(4-tert-butylphenyl)iodonium cation, etc.

Specific examples of suitable cations represented by the formula (ca-3) include the cations represented by the following formulas (ca-3-1) to (ca-3-6).

Specific examples of suitable cations represented by the formula (ca-4) include the cations represented by the following formulas (ca-4-1) to (ca-4-2).

Among the above, the cationic portion ((M' ^m+ ) _1/m ) is preferably a cation represented by general formula (ca-1). From the viewpoint of maintaining transparency in the thick resist film, in general formula (ca-1), at least one of R ²⁰² to R ²⁰³ is preferably an alkyl group or an alkenyl group, more preferably two or more of R ²⁰² to R ²⁰³ are alkyl groups or alkenyl groups, and even more preferably two or more of R ²⁰² to R ²⁰³ are alkyl groups. When two or more of R ²⁰² to R ²⁰³ are alkyl groups or alkenyl groups, the two of them may be mutually bonded to form a ring together with the sulfur atom in the formula. As the cation represented by general formula (ca-1), a cation represented by any one of the above formulas (ca-1-55) to (ca-1-68) is preferable, and a cation represented by any one of the above formulas (ca-1-63) to (ca-1-68) is more preferable.

Among these, the compound represented by the following general formula (b1-1) is particularly preferred as component (B1).

［式中、Ｒｂ^２０１は置換基を有してもよいアリール基である。Ｒｂ^２０２及びＲｂ^２０３は、それぞれ独立に、置換基を有していてもよいアルキル基または置換基を有してもよいアルケニル基である。Ｒｂ^２０２及びＲｂ^２０３は、相互に結合して式中のイオウ原子と共に環を形成してもよい。Ｒ^１０１は、置換基を有していてもよい環式基、置換基を有していてもよい鎖状のアルキル基、又は置換基を有していてもよい鎖状のアルケニル基である。Ｒ^１０２は、炭素数１～５のフッ素化アルキル基又はフッ素原子である。Ｙ^１０１は、酸素原子を含む２価の連結基又は単結合である。Ｖ^１０１は、単結合、アルキレン基又はフッ素化アルキレン基である。］

[In the formula, Rb ²⁰¹ is an aryl group which may have a substituent. Rb ²⁰² and Rb ²⁰³ are each independently an alkyl group which may have a substituent or an alkenyl group which may have a substituent. Rb ²⁰² and Rb ²⁰³ may be bonded to each other to form a ring together with the sulfur atom in the formula. R ¹⁰¹ is a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent. R ¹⁰² is a fluorinated alkyl group having 1 to 5 carbon atoms or a fluorine atom. Y ¹⁰¹ is a divalent linking group containing an oxygen atom or a single bond. V ¹⁰¹ is a single bond, an alkylene group, or a fluorinated alkylene group.]

In the formula (b1-1), the aryl group which may have a substituent in Rb ²⁰¹ is the same as the aryl group which may have a substituent in R ²⁰¹ in the formula (ca-1). Among them, Rb ²⁰¹ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
In the formula (b1-1), the alkyl group which may have a substituent or the alkenyl group which may have a substituent in Rb ²⁰² and Rb ²⁰³ are the same as the alkyl group which may have a substituent or the alkenyl group which may have a substituent in R ²⁰² and R ²⁰³ in the formula (ca-1). Among them, Rb ²⁰² and Rb ²⁰³ are preferably linear alkyl groups having 1 to 5 carbon atoms, and it is more preferable that Rb ²⁰² and Rb ²⁰³ are mutually bonded to form a 5-membered or 6-membered ring together with the sulfur atom in the formula.
In the formula (b1-1), R ¹⁰¹ , R ¹⁰² , Y ¹⁰¹ and V ¹⁰¹ are the same as R ¹⁰¹ , R ¹⁰² , Y ¹⁰¹ and V ¹⁰¹ in the formula (b-1).

Regarding the (B2) component: The (B) component may contain an acid generator component (hereinafter referred to as "(B2) component") that does not fall under the category of the above-mentioned (B1) component. The (B2) component is not particularly limited as long as it generates an acid upon exposure and does not fall under the category of the above-mentioned (B1) component, and may be arbitrarily selected from known components. Examples of the (B2) component include various types such as oxime sulfonate-based acid generators; diazomethane-based acid generators such as bisalkyl or bisaryl sulfonyl diazomethanes and poly(bissulfonyl) diazomethanes; nitrobenzyl sulfonate-based acid generators, iminosulfonate-based acid generators, and disulfone-based acid generators.

In the resist composition of this embodiment, the component (B) may use either a single type, or a combination of two or more types.
When the resist composition contains the component (B), the amount of the component (B) in the resist composition is preferably less than 50 parts by mass, more preferably 0.1 to 40 parts by mass, and even more preferably 0.3 to 25 parts by mass, relative to 100 parts by mass of the component (A).
By setting the content of the component (B) within the above-mentioned preferred range, sufficient pattern formation can be achieved. Furthermore, when the components of the resist composition are dissolved in an organic solvent, a homogeneous solution is easily obtained, and the storage stability of the resist composition is also favorable.

<<Base component (D)>>
The resist composition of this embodiment may further contain, in addition to the components (A) and (Z), a base component (component (D)) that traps acid generated upon exposure (i.e., controls the diffusion of acid). The component (D) acts as a quencher (acid diffusion controller) that traps acid generated in the resist composition upon exposure.
Examples of the component (D) include a photodegradable base (D1) (hereinafter referred to as "component (D1)") that decomposes upon exposure to light and loses its acid diffusion controllability, and a nitrogen-containing organic compound (D2) (hereinafter referred to as "component (D2)") that does not fall under the category of component (D1). Of these, the nitrogen-containing organic compound (D2) (component (D2)) is preferred from the viewpoint of maintaining sensitivity in the thick resist film. Of the component (D2), a chain alkylamine is more preferred from the viewpoint of maintaining transparency in the thick resist film.

- Component (D1) By using a resist composition that contains the component (D1), the contrast between exposed and unexposed areas of the resist film can be further improved when forming a resist pattern.
The component (D1) is not particularly limited as long as it decomposes upon exposure to light and loses its acid diffusion controllability, and is preferably one or more compounds selected from the group consisting of a compound represented by the following general formula (d1-1) (hereinafter referred to as "component (d1-1)"), a compound represented by the following general formula (d1-2) (hereinafter referred to as "component (d1-2)"), and a compound represented by the following general formula (d1-3) (hereinafter referred to as "component (d1-3)"):
The components (d1-1) to (d1-3) do not act as quenchers in the exposed areas of the resist film because they decompose and lose their acid diffusion control ability (basicity), but act as quenchers in the unexposed areas of the resist film.

［式中、Ｒｄ^１～Ｒｄ^４は置換基を有していてもよい環式基、置換基を有していてもよい鎖状のアルキル基、又は置換基を有していてもよい鎖状のアルケニル基である。但し、式（ｄ１－２）中のＲｄ^２における、Ｓ原子に隣接する炭素原子にはフッ素原子は結合していないものとする。Ｙｄ^１は単結合又は２価の連結基である。ｍは１以上の整数であって、Ｍ^ｍ＋はそれぞれ独立にｍ価の有機カチオンである。］

[In the formula, Rd ¹ to Rd ⁴ are a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent. However, in Rd ² in formula (d1-2), a fluorine atom is not bonded to the carbon atom adjacent to the S atom. ^{Yd 1} is a single bond or a divalent linking group. m is an integer of 1 or more, and each M ^m+ is independently an m-valent organic cation.]

{(d1-1) component}
In formula (d1-1), Rd ¹ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples of these groups include the same as those for R' ²⁰¹ described above.
Among these, Rd ¹ is preferably an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain-like alkyl group which may have a substituent. Examples of the substituent which these groups may have include a hydroxyl group, an oxo group, an alkyl group, an aryl group, a fluorine atom, a fluorinated alkyl group, a lactone-containing cyclic group represented by each of the above general formulas (a2-r-1) to (a2-r-7), an ether bond, an ester bond, or a combination thereof. When an ether bond or an ester bond is contained as a substituent, it may be via an alkylene group, and in this case, the substituent is preferably a linking group represented by each of the above formulas (y-al-1) to (y-al-5).
Suitable examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, and a polycyclic structure containing a bicyclooctane skeleton (a polycyclic structure consisting of a bicyclooctane skeleton and another ring structure).
The aliphatic cyclic group is more preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.
The chain alkyl group preferably has 1 to 10 carbon atoms. Specific examples of the chain alkyl group include linear alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group; and branched alkyl groups such as a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

When the chain-like alkyl group is a fluorinated alkyl group having a fluorine atom or a fluorinated alkyl group as a substituent, the number of carbon atoms in the fluorinated alkyl group is preferably 1 to 11, more preferably 1 to 8, and further preferably 1 to 4. The fluorinated alkyl group may contain an atom other than a fluorine atom. Examples of the atom other than a fluorine atom include an oxygen atom, a sulfur atom, and a nitrogen atom.
^Rd1 is preferably a fluorinated alkyl group in which some or all of the hydrogen atoms constituting a linear alkyl group have been substituted with fluorine atoms, and particularly preferably a fluorinated alkyl group in which all of the hydrogen atoms constituting a linear alkyl group have been substituted with fluorine atoms (linear perfluoroalkyl group).

Specific examples of preferred anion moieties of component (d1-1) are shown below.

In formula (d1-1), M ^m+ represents an m-valent organic cation.
Suitable examples of the organic cation of M ^m+ include the same cations as those represented by the general formulas (ca-1) to (ca-4), respectively, more preferably the cation represented by the general formula (ca-1), and even more preferably the cations represented by the general formulas (ca-1-1) to (ca-1-70).
The component (d1-1) may be used alone or in combination of two or more.

{(d1-2) component}
In formula (d1-2), ^Rd2 represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples of R'201 include the same as those described above for ^R'201 .
However, in ^Rd2 , the carbon atom adjacent to the S atom does not have a fluorine atom bonded thereto (is not substituted with fluorine), whereby the anion of the component (d1-2) becomes an appropriately weak acid anion, and the quenching ability of the component (D) is improved.
^Rd2 is preferably a chain alkyl group which may have a substituent, or an aliphatic cyclic group which may have a substituent. The chain alkyl group preferably has 1 to 10 carbon atoms, and more preferably has 3 to 10 carbon atoms. The aliphatic cyclic group is more preferably a group (which may have a substituent) in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like; or a group in which one or more hydrogen atoms have been removed from camphor, or the like.
The hydrocarbon group of ^Rd2 may have a substituent, and examples of the substituent include the same substituents as those that may be possessed by the hydrocarbon group (aromatic hydrocarbon group, aliphatic cyclic group, chain alkyl group) in ^Rd1 of the above formula (d1-1).

Preferred specific examples of the anion portion of component (d1-2) are shown below.

Cation Moiety In formula (d1-2), M ^m+ represents an m-valent organic cation and is the same as M ^m+ in formula (d1-1).
The component (d1-2) may be used alone or in combination of two or more.

{(d1-3) component}
In formula (d1-3), Rd ³ is a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples thereof include the same as those of R' ²⁰¹ , and is preferably a cyclic group, chain alkyl group, or chain alkenyl group containing a fluorine atom. Among them, a fluorinated alkyl group is preferable, and the same as the fluorinated alkyl group of Rd ¹ is more preferable.

In formula (d1-3), ^Rd4 represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent, and examples of ^R'201 include the same as those described above.
Among these, an alkyl group, an alkoxy group, an alkenyl group, or a cyclic group, each of which may have a substituent, is preferable.
The alkyl group in Rd ⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, etc. A part of the hydrogen atoms of the alkyl group in Rd ⁴ may be substituted with a hydroxyl group, a cyano group, etc.
The alkoxy group in Rd ⁴ is preferably an alkoxy group having 1 to 5 carbon atoms, and specific examples of the alkoxy group having 1 to 5 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, and a tert-butoxy group. Of these, a methoxy group and an ethoxy group are preferable.

The alkenyl group in ^Rd4 may be the same as the alkenyl group in ^R'201 , and preferably a vinyl group, a propenyl group (allyl group), a 1-methylpropenyl group, or a 2-methylpropenyl group. These groups may further have an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms as a substituent.

Examples of the cyclic group in Rd ⁴ include the same as the cyclic group in R' ²⁰¹ , and are preferably an alicyclic group obtained by removing one or more hydrogen atoms from a cycloalkane such as cyclopentane, cyclohexane, adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane, or an aromatic group such as a phenyl group or naphthyl group. When Rd ⁴ is an alicyclic group, the resist composition dissolves well in an organic solvent, thereby improving the lithography properties. In addition, when Rd ⁴ is an aromatic group, in lithography using EUV or the like as an exposure light source, the resist composition has excellent light absorption efficiency, and the sensitivity and lithography properties are improved.

In formula (d1-3), ^Yd1 represents a single bond or a divalent linking group.
The divalent linking group in Yd ¹ is not particularly limited, and examples thereof include a divalent hydrocarbon group which may have a substituent (an aliphatic hydrocarbon group, an aromatic hydrocarbon group), a divalent linking group containing a hetero atom, etc. These include the same as the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom mentioned in the description of the divalent linking group in Ya ²¹ in the above formula (a2-1).
^Yd1 is preferably a carbonyl group, an ester bond, an amide bond, an alkylene group, or a combination thereof. The alkylene group is more preferably a linear or branched alkylene group, and further preferably a methylene group or an ethylene group.

Specific examples of preferred anion moieties of component (d1-3) are shown below.

Cation Moiety In formula (d1-3), M ^m+ represents an m-valent organic cation and is the same as M ^m+ in formula (d1-1).
The component (d1-3) may be used alone or in combination of two or more.

The component (D1) may be any one of the above components (d1-1) to (d1-3), or a combination of two or more of them.
When the resist composition contains the component (D1), the amount of the component (D1) in the resist composition is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 5 to 10 parts by mass, relative to 100 parts by mass of the component (A).
When the content of the component (D1) is at least the preferred lower limit, particularly good lithography properties and resist pattern shape are likely to be obtained, while when it is no more than the upper limit, good sensitivity can be maintained and throughput is also excellent.

Production method of component (D1):
The method for producing the components (d1-1) and (d1-2) is not particularly limited, and they can be produced by known methods.
The method for producing the component (d1-3) is not particularly limited, and it can be produced, for example, in the same manner as the method described in US 2012-0149916.

Regarding the component (D2): The component (D) preferably contains a nitrogen-containing organic compound component (hereinafter referred to as "component (D2)") that does not fall under the category of the above-mentioned component (D1).
The component (D2) is not particularly limited as long as it acts as an acid diffusion controller and does not fall under the category of component (D1), and any known component may be used. Among these, aliphatic amines are preferred, and among these, secondary aliphatic amines and tertiary aliphatic amines are more preferred.
An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 12 carbon atoms.
Examples of aliphatic amines include amines in which at least one hydrogen atom of ammonia _NH3 is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms (alkylamines or alkyl alcohol amines), or cyclic amines.
Specific examples of alkylamines and alkyl alcohol amines include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, and n-decylamine; dialkylamines such as diethylamine, di-n-propylamine, di-n-heptylamine, di-n-octylamine, and dicyclohexylamine; trialkylamines such as trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkyl alcohol amines such as diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n-octanolamine, and tri-n-octanolamine. Among these, trialkylamines having 5 to 10 carbon atoms are more preferred, and tri-n-pentylamine or tri-n-octylamine is particularly preferred.

Examples of cyclic amines include heterocyclic compounds containing a nitrogen atom as a heteroatom. The heterocyclic compounds may be monocyclic (aliphatic monocyclic amines) or polycyclic (aliphatic polycyclic amines).
Specific examples of the aliphatic monocyclic amine include piperidine and piperazine.
The aliphatic polycyclic amine is preferably one having 6 to 10 carbon atoms, and specific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and 1,4-diazabicyclo[2.2.2]octane.

Other aliphatic amines include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, triethanolamine triacetate, etc., with triethanolamine triacetate being preferred.

Furthermore, an aromatic amine may be used as the component (D2).
Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole or derivatives thereof, tribenzylamine, 2,6-diisopropylaniline, and N-tert-butoxycarbonylpyrrolidine.

From the viewpoint of maintaining transparency in the thick-film resist, the (D2) component is preferably an aliphatic amine, more preferably a chain aliphatic amine, and even more preferably a chain alkylamine. The chain alkyl group of the chain alkylamine preferably has 5 to 10 carbon atoms. Among these, dialkylamines or trialkylamines having a linear alkyl group with 5 to 10 carbon atoms are preferred, and trialkylamines are more preferred.

The component (D2) may be used alone or in combination of two or more types.
When the resist composition contains the component (D2), the amount of the component (D2) in the resist composition is typically within the range from 0.005 to 5 parts by mass relative to 100 parts by mass of the component (A). By ensuring that the amount is within this range, the resist pattern shape, the storage stability over time, and the like are improved.

<At least one compound (E) selected from the group consisting of organic carboxylic acids, phosphorus oxoacids and derivatives thereof>
For the purposes of preventing deterioration of sensitivity and improving the resist pattern shape and storage stability, etc., the resist composition of this embodiment may contain, as an optional component, at least one compound (E) selected from the group consisting of organic carboxylic acids, and phosphorus oxoacids and derivatives thereof (hereafter referred to as "component (E)").
Suitable organic carboxylic acids include, for example, acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.
Examples of phosphorus oxoacids include phosphoric acid, phosphonic acid, and phosphinic acid, with phosphonic acid being particularly preferred.
Examples of derivatives of phosphorus oxoacids include esters in which the hydrogen atoms of the above oxoacids are substituted with hydrocarbon groups. Examples of the hydrocarbon groups include alkyl groups having 1 to 5 carbon atoms and aryl groups having 6 to 15 carbon atoms.
Examples of the derivatives of phosphoric acid include phosphoric acid esters such as di-n-butyl phosphoric acid ester and diphenyl phosphoric acid ester.
Examples of the derivatives of phosphonic acid include phosphonic acid esters such as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid, diphenyl phosphonate, and dibenzyl phosphonate.
Derivatives of phosphinic acid include phosphinic acid esters and phenylphosphinic acid.
In the resist composition of this embodiment, the component (E) may use either a single type, or a combination of two or more types.
When the resist composition contains the component (E), the amount of the component (E) is typically within a range from 0.01 to 5 parts by mass per 100 parts by mass of the component (A).

<Fluorine additive component (F)>
The resist composition of this embodiment may contain a fluorine additive component (hereafter referred to as “component (F)”) in order to impart water repellency to the resist film or to improve lithography properties.
As the component (F), for example, the fluorine-containing polymeric compounds described in JP-A-2010-002870, JP-A-2010-032994, JP-A-2010-277043, JP-A-2011-13569, and JP-A-2011-128226 can be used.
More specifically, the component (F) may be a polymer having a structural unit (f1) represented by the following general formula (f1-1). This polymer is preferably a polymer (homopolymer) consisting only of the structural unit (f1) represented by the following formula (f1-1); a copolymer of the structural unit (f1) and the structural unit (a1); or a copolymer of the structural unit (f1), a structural unit derived from acrylic acid or methacrylic acid, and the structural unit (a1). Here, the structural unit (a1) copolymerized with the structural unit (f1) is preferably a structural unit derived from 1-ethyl-1-cyclooctyl (meth)acrylate or a structural unit derived from 1-methyl-1-adamantyl (meth)acrylate.

［式中、Ｒは前記と同様であり、Ｒｆ^１０２およびＲｆ^１０３はそれぞれ独立して水素原子、ハロゲン原子、炭素数１～５のアルキル基又は炭素数１～５のハロゲン化アルキル基を表し、Ｒｆ^１０２およびＲｆ^１０３は同じであっても異なっていてもよい。ｎｆ^１は１～５の整数であり、Ｒｆ^１０１はフッ素原子を含む有機基である。］

[In the formula, R is the same as above, Rf ¹⁰² and Rf ¹⁰³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, and Rf ¹⁰² and Rf ¹⁰³ may be the same or different. nf ¹ is an integer of 1 to 5, and Rf ¹⁰¹ is an organic group containing a fluorine atom.]

In formula (f1-1), R bonded to the carbon atom at the α-position is the same as defined above. R is preferably a hydrogen atom or a methyl group.
In formula (f1-1), examples of halogen atoms of Rf ¹⁰² and Rf ¹⁰³ include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc., with fluorine atoms being particularly preferred. Examples of alkyl groups having 1 to 5 carbon atoms of Rf ¹⁰² and Rf ¹⁰³ include the same as the alkyl groups having 1 to 5 carbon atoms of R above, with methyl groups or ethyl groups being preferred. Specific examples of halogenated alkyl groups having 1 to 5 carbon atoms of Rf ¹⁰² and Rf ¹⁰³ include groups in which some or all of the hydrogen atoms of an alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc., with fluorine atoms being particularly preferred. Among these, examples of Rf ¹⁰² and Rf ¹⁰³ include hydrogen atoms, fluorine atoms, or alkyl groups having 1 to 5 carbon atoms, with hydrogen atoms, fluorine atoms, methyl groups, or ethyl groups being preferred.
In formula (f1-1), nf ¹ represents an integer of 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf ¹⁰¹ is an organic group containing a fluorine atom, and is preferably a hydrocarbon group containing a fluorine atom.
The fluorine atom-containing hydrocarbon group may be linear, branched or cyclic and preferably has 1 to 20 carbon atoms, more preferably has 1 to 15 carbon atoms, and particularly preferably has 1 to 10 carbon atoms.
In addition, in the hydrocarbon group containing fluorine atoms, preferably 25% or more of the hydrogen atoms in the hydrocarbon group are fluorinated, more preferably 50% or more, and particularly preferably 60% or more are fluorinated, as this enhances the hydrophobicity of the resist film during immersion exposure.
Of these, Rf ¹⁰¹ is more preferably a fluorinated hydrocarbon group having 1 to 6 carbon atoms, with a trifluoromethyl group, -CH ₂ -CF ₃ , -CH ₂ -CF ₂ -CF ₃ , -CH(CF ₃ ) ₂ , -CH ₂ -CH ₂ -CF ₃ , and -CH ₂ -CH ₂ -CF ₂ -CF ₂ -CF ₂ -CF ₃ being particularly preferred.

The weight average molecular weight (Mw) of component (F) (based on polystyrene equivalent measured by gel permeation chromatography) is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and most preferably 10,000 to 30,000. When it is below the upper limit of this range, the compound has sufficient solubility in a resist solvent for use as a resist, and when it is above the lower limit of this range, the resist film has good water repellency.
The dispersity (Mw/Mn) of the component (F) is preferably from 1.0 to 5.0, more preferably from 1.0 to 3.0, and most preferably from 1.0 to 2.5.

In the resist composition of this embodiment, the component (F) may use either a single type, or a combination of two or more types.
When the resist composition contains the component (F), the component (F) is typically used in an amount of 0.5 to 10 parts by mass per 100 parts by mass of the component (A).

<Organic solvent component (S)>
The resist composition of this embodiment can be produced by dissolving the resist materials in an organic solvent component (hereafter referred to as “component (S)”).
The component (S) can be any solvent that is capable of dissolving the individual components used and forming a homogeneous solution, and any solvent can be appropriately selected from those that are conventionally known as solvents for chemically amplified resist compositions.
Examples of the component (S) include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol; compounds having an ester bond such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; and compounds having an ether bond such as monoalkyl ethers, monoethyl ethers, monopropyl ethers, and monobutyl ethers of the polyhydric alcohols or compounds having an ester bond, or monophenyl ethers. and derivatives of polyhydric alcohols such as those listed above (among which, propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferred)]; cyclic ethers such as dioxane, esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; aromatic organic solvents such as anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, dibenzyl ether, phenetole, butyl phenyl ether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene, and mesitylene, and dimethyl sulfoxide (DMSO).
In the resist composition of this embodiment, the component (S) may be used alone or as a mixed solvent of two or more kinds. Among them, at least one selected from the group consisting of PGMEA, PGME, γ-butyrolactone, EL, butyl acetate, and cyclohexanone is preferable, and at least one selected from the group consisting of PGMEA, PGME, and butyl acetate is more preferable.

As the component (S), a mixed solvent of PGMEA and a polar solvent is also preferred. The blending ratio (mass ratio) may be appropriately determined taking into consideration the compatibility between PGMEA and the polar solvent, and is preferably within the range of 1:9 to 9:1, and more preferably 2:8 to 8:2.
More specifically, when EL, butyl acetate or cyclohexanone is blended as the polar solvent, the mass ratio of PGMEA:EL, butyl acetate or cyclohexanone is preferably 1:9 to 9:1, more preferably 2:8 to 8:2. When PGME is blended as the polar solvent, the mass ratio of PGMEA:PGME is preferably 1:9 to 9:1, more preferably 2:8 to 8:2, and even more preferably 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME and butyl acetate is also preferred.
As the component (S), a mixed solvent of at least one selected from PGMEA and EL with γ-butyrolactone is also preferred. In this case, the mixing ratio of the former to the latter is preferably 70:30 to 95:5 by mass.

The amount of component (S) used is set so that the solids concentration of the resist composition is 25 mass % or more. In this specification, the solids content of the resist composition refers to the components other than component (S). The solids concentration of the resist composition is calculated according to the following formula.
Solid content concentration (mass %)=total mass of components other than component (S)/total mass of resist composition×100

For example, when the resist composition is composed of the (A) component, the (Z) component, the (B) component, the (D) component, and the (S) component, the solids concentration (mass %) = [((A) component + (Z) component + (B) component + (D) component) / ((A) component + (Z) component + (B) component + (D) component) + (S) component] x 100.

By making the solid content concentration of the resist composition 25 mass% or more, when the resist composition is applied to a substrate to form a resist film, a thick resist film (for example, a film thickness of 5 μm or more, preferably 7 μm or more) can be formed. The solid content concentration of the resist composition is not particularly limited as long as it is 25 mass% or more, and can be appropriately determined according to the desired film thickness of the resist film. In general, the higher the solid content concentration, the thicker the film thickness of the resist film.
The upper limit of the solid content concentration of the resist composition is not particularly limited as long as the solid content is soluble in the resist composition. The solid content concentration of the resist composition is, for example, 60% by mass or less, preferably 55% by mass or less, and more preferably 50% by mass or less.
The solid content of the resist composition may be in the range of, for example, 25 to 60% by mass, 25 to 55% by mass, or 25 to 50% by mass.

The resist composition of this embodiment may further contain compatible additives, such as additional resins for improving the performance of the resist film, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, dyes, etc., as desired.

After dissolving the resist material in the (S) component, the resist composition of this embodiment may be subjected to removal of impurities using a polyimide porous film, a polyamideimide porous film, or the like. For example, the resist composition may be filtered using a filter made of a polyimide porous film, a filter made of a polyamideimide porous film, or a filter made of a polyimide porous film and a polyamideimide porous film. Examples of the polyimide porous film and the polyamideimide porous film include those described in JP 2016-155121 A.

The resist composition of this embodiment described above has a solids concentration of 25 mass % or more and contains the ionic liquid (Z).
The resist composition of this embodiment has a solid content concentration of 25% by mass or more, so when it is applied to a substrate to form a resist film, a thick resist film (for example, a film thickness of 5 μm or more) is formed. In such a thick resist film, cracks are likely to occur in the resist pattern. In addition, since light does not easily reach the bottom, it is difficult to maintain sensitivity during exposure, and it is difficult to form a resist pattern with a good shape.
The resist composition of the present embodiment can achieve both crack resistance and high sensitivity by containing the ionic liquid (Z). This is presumably because the stress of the resist film is alleviated by the presence of the ionic liquid (Z) in the resist film formed using the resist composition.

(Method of forming a resist pattern)
A method for forming a resist pattern according to a second aspect of the present invention is a method comprising the steps of forming a resist film on a support using the resist composition of the above-described embodiment, exposing the resist film to light, and developing the exposed resist film to form a resist pattern.
One embodiment of the resist pattern forming method is, for example, a resist pattern forming method carried out as follows.

First, the resist composition of the above-described embodiment is applied onto a support using a spinner or the like, and then baked (post-applied bake (PAB)) at a temperature of, for example, 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.
Next, the resist film is selectively exposed using an exposure apparatus such as an electron beam lithography apparatus or an EUV exposure apparatus, either through a mask (mask pattern) having a predetermined pattern formed thereon, or by lithography using direct irradiation with an electron beam without using a mask pattern, and then baked (post-exposure bake (PEB)) at a temperature of, for example, 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds.
Next, the resist film is developed using an alkaline developer in the case of an alkaline development process, or a developer containing an organic solvent (organic developer) in the case of a solvent development process.

After the development process, a rinse process is preferably carried out. In the case of an alkaline development process, the rinse process is preferably a water rinse using pure water, and in the case of a solvent development process, a rinse liquid containing an organic solvent is preferably used.
In the case of a solvent development process, after the development treatment or rinsing treatment, a treatment may be carried out in which the developer or rinsing liquid adhering to the pattern is removed by using a supercritical fluid.
After the development treatment or rinsing treatment, drying is performed. In some cases, a baking treatment (post-baking) may be performed after the development treatment.
In this manner, a resist pattern can be formed.

The support is not particularly limited, and may be a conventionally known support, such as a substrate for electronic components or a substrate on which a predetermined wiring pattern is formed. More specifically, it may be a silicon wafer, a substrate made of metal such as copper, chromium, iron, or aluminum, or a glass substrate. As the material for the wiring pattern, for example, copper, aluminum, nickel, or gold may be used.
The support may be a substrate as described above on which an inorganic and/or organic film is provided. Examples of inorganic films include inorganic anti-reflective coatings (inorganic BARC). Examples of organic films include organic anti-reflective coatings (organic BARC) and organic films such as lower organic films in a multi-layer resist method.
Here, the multi-layer resist method is a method in which at least one organic film (lower organic film) and at least one resist film (upper resist film) are provided on a substrate, and the lower organic film is patterned using the resist pattern formed on the upper resist film as a mask, and it is said that a pattern with a high aspect ratio can be formed. That is, according to the multi-layer resist method, the required thickness can be secured by the lower organic film, so that the resist film can be made thin, and a fine pattern with a high aspect ratio can be formed.
Multilayer resist methods are basically divided into a method in which a two-layer structure consisting of an upper resist film and a lower organic film is formed (two-layer resist method), and a method in which a multilayer structure consisting of three or more layers is formed by providing one or more intermediate layers (such as a thin metal film) between an upper resist film and a lower organic film (three-layer resist method).

In the resist pattern forming method of this embodiment, since the resist composition of the above-mentioned embodiment is used, a thick resist film is formed in step (i). The thickness of the resist film is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 8 μm or more. The upper limit of the thickness of the resist film is, for example, 30 μm or less. The range of the thickness of the resist film formed in step (i) is, for example, 5 to 30 μm, preferably 7 to 20 μm, more preferably 7 to 15 μm, and even more preferably 8 to 12 μm. The thickness of the resist film can be adjusted by the solid content concentration of the resist composition used in step (i). That is, the higher the solid content concentration of the resist composition, the thicker the resist film can be formed.

The wavelength used for exposure is not particularly limited, and radiation such as ArF excimer laser, KrF excimer laser, _F2 excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. The resist composition is highly useful for KrF excimer laser, ArF excimer laser, EB or EUV, more useful for KrF excimer laser or ArF excimer laser, and particularly useful for KrF excimer laser. That is, the resist pattern forming method of this embodiment is a particularly useful method when the step of exposing the resist film includes an operation of exposing the resist film to KrF excimer laser light.

The exposure method for the resist film may be a normal exposure method (dry exposure) performed in air or an inert gas such as nitrogen, or may be liquid immersion exposure (liquid immersion lithography).
Immersion exposure is an exposure method in which the space between the resist film and the lowest lens of the exposure tool is filled with a solvent (immersion medium) that has a refractive index greater than that of air, and exposure (immersion exposure) is then performed in that state.
The immersion medium is preferably a solvent having a refractive index larger than that of air and smaller than that of the resist film to be exposed. The refractive index of the solvent is not particularly limited as long as it is within the above range.
Examples of the solvent having a refractive index larger than that of air and smaller than that of the resist film include water, a fluorine-based inert liquid, a silicon-based solvent, and a hydrocarbon-based solvent.
Specific examples of the fluorine-based inert liquid include liquids _{mainly composed of fluorine-based compounds such as C3HCl2F5, C4F9OCH3, C4F9OC2H5 , and C5H3F7 , and preferably have a} boiling point of 70 to ₁₈₀ ° C., more preferably 80 to 160 _{° C.} If the fluorine-based inert liquid has a boiling point in the above range, _it is preferable because the medium used for immersion can be removed in a simple manner after exposure is completed.
As the fluorine-based inert liquid, a perfluoroalkyl compound in which all hydrogen atoms of the alkyl group are replaced with fluorine atoms is particularly preferred. Specific examples of the perfluoroalkyl compound include perfluoroalkyl ether compounds and perfluoroalkylamine compounds.
More specifically, the perfluoroalkyl ether compound may be perfluoro(2-butyl-tetrahydrofuran) (boiling point: 102° C.), and the perfluoroalkylamine compound may be perfluorotributylamine (boiling point: 174° C.).
As the liquid immersion medium, water is preferably used from the viewpoints of cost, safety, environmental issues, versatility, and the like.

The alkaline developer used in the development treatment in the alkaline development process may be, for example, a 0.1 to 10% by weight aqueous solution of tetramethylammonium hydroxide (TMAH).
The organic solvent contained in the organic developer used in the development treatment in the solvent development process may be any organic solvent capable of dissolving the component (A) (the component (A) before exposure), and may be appropriately selected from known organic solvents. Specific examples of the organic solvent include polar solvents such as ketone solvents, ester solvents, alcohol solvents, nitrile solvents, amide solvents, and ether solvents, and hydrocarbon solvents.
Ketone-based solvents are organic solvents that contain C-C(=O)-C in their structure. Ester-based solvents are organic solvents that contain C-C(=O)-O-C in their structure. Alcohol-based solvents are organic solvents that contain an alcoholic hydroxyl group in their structure. "Alcoholic hydroxyl group" means a hydroxyl group bonded to a carbon atom of an aliphatic hydrocarbon group. Nitrile-based solvents are organic solvents that contain a nitrile group in their structure. Amide-based solvents are organic solvents that contain an amide group in their structure. Ether-based solvents are organic solvents that contain C-O-C in their structure.
Some organic solvents contain multiple types of functional groups that characterize the above-mentioned solvents in their structures, and in such cases, the organic solvent is considered to fall under any of the solvent types that contain the functional groups possessed by the organic solvent. For example, diethylene glycol monomethyl ether is considered to fall under both the alcohol-based solvents and the ether-based solvents in the above classification.
The hydrocarbon solvent is a hydrocarbon solvent that is composed of a hydrocarbon that may be halogenated and has no substituents other than halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferred.
Of the above, the organic solvent contained in the organic developer is preferably a polar solvent, and more preferably a ketone solvent, an ester solvent, a nitrile solvent, or the like.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, propylene carbonate, γ-butyrolactone, and methyl amyl ketone (2-heptanone). Of these, methyl amyl ketone (2-heptanone) is preferred as a ketone solvent.

Examples of ester solvents include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, methoxyethyl acetate, ethoxyethyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, propylene glycol monoethyl ether acetate, propylene glycol monoethyl ether acetate, 2-ethoxybutyl ... dibutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, proline lactate Examples of the ester-based solvent include pyrulic acid, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, and propyl 3-methoxypropionate. Among these, butyl acetate is preferred as the ester-based solvent.

Examples of nitrile solvents include acetonitrile, propionitrile, valeronitrile, butyronitrile, etc.

The organic developer may contain known additives as necessary. Examples of such additives include surfactants. The surfactant is not particularly limited, but may be, for example, an ionic or nonionic fluorine-based and/or silicon-based surfactant. The surfactant is preferably a nonionic surfactant, more preferably a nonionic fluorine-based surfactant or a nonionic silicon-based surfactant.
When a surfactant is added, the amount of the surfactant added is usually from 0.001 to 5% by mass, preferably from 0.005 to 2% by mass, and more preferably from 0.01 to 0.5% by mass, based on the total amount of the organic developer.

The development process can be carried out by a known development method, such as a method of immersing the support in a developer for a certain period of time (dip method), a method of piling up the developer on the support surface by surface tension and leaving it still for a certain period of time (paddle method), a method of spraying the developer on the support surface (spray method), or a method of continuously applying developer while scanning a developer application nozzle at a constant speed onto a support rotating at a constant speed (dynamic dispense method).

The organic solvent contained in the rinse solution used in the rinse treatment after the development treatment in the solvent development process can be selected appropriately from the organic solvents listed as the organic solvents used in the organic developer, and can be used if it is difficult to dissolve the resist pattern.Usually, at least one solvent selected from a hydrocarbon solvent, a ketone solvent, an ester solvent, an alcohol solvent, an amide solvent, and an ether solvent is used.Among these, at least one solvent selected from a hydrocarbon solvent, a ketone solvent, an ester solvent, an alcohol solvent, and an amide solvent is preferred, at least one solvent selected from an alcohol solvent and an ester solvent is more preferred, and an alcohol solvent is particularly preferred.
The alcohol-based solvent used in the rinse liquid is preferably a monohydric alcohol having 6 to 8 carbon atoms, and the monohydric alcohol may be any of linear, branched, and cyclic. Specific examples include 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, and benzyl alcohol. Among these, 1-hexanol, 2-heptanol, and 2-hexanol are preferred, and 1-hexanol and 2-hexanol are more preferred.
These organic solvents may be used alone or in combination of two or more. They may also be used in combination with other organic solvents or water. However, in consideration of development characteristics, the amount of water in the rinse solution is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, based on the total amount of the rinse solution.
The rinse solution may contain known additives as necessary. Examples of such additives include surfactants. The surfactants include those similar to those described above, and nonionic surfactants are preferred, and nonionic fluorine-based surfactants or nonionic silicon-based surfactants are more preferred.
When a surfactant is added, the amount of the surfactant added is usually 0.001 to 5 mass %, preferably 0.005 to 2 mass %, and more preferably 0.01 to 0.5 mass %, based on the total amount of the rinse solution.

The rinse treatment (cleaning treatment) using a rinse solution can be carried out by a known rinse method. Examples of the rinse treatment method include a method in which the rinse solution is continuously applied onto a support rotating at a constant speed (spin coating method), a method in which the support is immersed in the rinse solution for a certain period of time (dip method), and a method in which the rinse solution is sprayed onto the surface of the support (spray method).

According to the resist pattern forming method of this embodiment described above, since the resist composition according to the first aspect described above is used, it is possible to achieve high sensitivity and form a resist pattern with fewer cracks.

This resist pattern formation method is useful for manufacturing three-dimensional structure devices.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of Resist Composition>
(Examples 1 to 12, Comparative Examples 1 and 2)
The components shown in Table 1 were mixed and dissolved to prepare resist compositions of each example.

In Table 1, the abbreviations have the following meanings. The numbers in brackets [ ] are the amounts used (parts by mass). The solids concentration was calculated by Solids Concentration (mass%) = [(Component (A) + Component (B) + Component (D) + Component (Z))/(Component (A) + Component (B) + Component (D) + Component (Z) + Component (S))] x 100.

(A)-1: Polymer compound represented by the following chemical formula (A-1). Standard polystyrene-equivalent weight average molecular weight (Mw) determined by GPC measurement is 10,000, and polydispersity (Mw/Mn) is 1.4. Copolymer composition ratio (proportion (molar ratio) of each structural unit in the structural formula) determined by ^13C -NMR is l/m/n=60/15/25.

(B)-1: An acid generator comprising a compound represented by the following chemical formula (B-1).
(D)-1: A nitrogen-containing organic compound represented by the following chemical formula (D-1).

(Z)-1: A compound represented by the following formula (IL)-1.
(Z)-2: A compound represented by the following formula (IL)-3.
(Z)-3: A compound represented by the following formula (IL)-14.
(Z)-4: A compound represented by the following formula (IL)-15.
(Z)-5: A compound represented by the following formula (IL)-16.
(Z)-6: A compound represented by the following formula (IL)-17.
(Z)-7: A compound represented by the following formula (IL)-18.
(Z)-8: A compound represented by the following formula (IL)-19.
(Z)-9: A compound represented by the following formula (IL)-20.

(S)-1: Propylene glycol monomethyl ether (S)-2: Propylene glycol monomethyl ether acetate (S)-3: Butyl acetate

<Formation of Resist Pattern>
Step (i):
Each resist composition of each example was applied using a spinner onto an 8-inch silicon wafer that had been treated with hexamethyldisilazane (HMDS) at 110° C. for 60 seconds. The wafer was then prebaked (PAB) on a hot plate at 140° C. for 90 seconds and dried to form a resist film with a thickness of 15 μm.
Step (ii):
Next, the resist film was selectively irradiated with a KrF excimer laser (248 nm) through a mask pattern (binary mask) using a KrF exposure system NSR-S203B (Nikon Corporation; NA (numerical aperture) = 0.68, σ = 0.40).
This was followed by a post-exposure bake (PEB) treatment at 110° C. for 90 seconds.
Step (iii):
Next, alkaline development was carried out using a 2.38% by mass tetramethylammonium hydroxide (TMAH) aqueous solution "NMD-3" (product name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) as a developer at 23° C. for 60 seconds.
Then, post-baking was performed at 100° C. for 60 seconds.
As a result, an isolated space pattern (hereinafter referred to as an "IS pattern") with a space width of 5 μm and a pitch of 30 μm was formed.

[Crack resistance evaluation]
The silicon wafer on which the IS pattern was formed by the above <Formation of Resist Pattern> was placed in the chamber of a scanning electron microscope S-9380 (manufactured by Hitachi High-Technologies Corporation) and subjected to a vacuum treatment under a pressure of 0.0001 Pa for 60 seconds. The silicon wafer after the vacuum treatment was observed using an optical microscope, and the number of cracks was counted. The number of cracks was evaluated based on the following evaluation criteria. The results are shown in Table 2 as "Cracks".
Evaluation criteria: ◎: 0 cracks; ◯: 1 to 5 cracks; ×: 6 or more cracks

[Sensitivity evaluation]
In the above <Formation of Resist Pattern>, the optimum exposure dose Eop (mJ/cm ^{2 ) for forming an IS pattern with a space width of 5 μm and a pitch of 30 μm was determined. This is shown in Table 2 as "Eop (mJ/cm 2 )} ".

The results shown in Table 2 confirm that the resist compositions of Examples 1 to 12 have good crack resistance and sensitivity.

Claims (5)

A resist composition which generates an acid upon exposure and changes its solubility in a developer by the action of the acid,
a base component (A) whose solubility in a developer changes under the action of an acid;
An ionic liquid (Z);
Contains
The content of the ionic liquid (Z) is 3 parts by mass or more and less than 25 parts by mass relative to 100 parts by mass of the base component (A) ,
A resist composition having a solids concentration of 25% by mass or more. The base component (A) comprises a structural unit (a1) represented by the following general formula (a1-1) or (a1-2):
A structural unit (a10) represented by general formula (a10-1) below,
The resist composition of claim 1 , having the formula:

[In the formula, R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ¹ is a divalent hydrocarbon group which may have an ether bond. _a1 is an integer from 0 to 2. ¹ is an acid dissociable group represented by the following general formula (a1-r-1) or (a1-r-2): ¹ is _a2 is a monovalent hydrocarbon group, n _a2 is an integer from 1 to 3, and Ra ² is an acid dissociable group represented by the following general formula (a1-r-1) or (a1-r-3).

[Wherein, Ra' ¹ , Ra' ² is a hydrogen atom or an alkyl group. ³ is a hydrocarbon group, ³ is Ra' ¹ , Ra' ² Ra' may be bonded to any one of the groups to form a ring. ⁴ ~Ra' ⁶ Each of Ra' is a hydrocarbon group, ⁵ , Ra' ⁶ may be bonded to each other to form a ring. ⁷ ~Ra' ⁹ Each of the groups is an alkyl group.

[In the formula, R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ^x1 is a single bond or a divalent linking group. ^x1 is (n _ax1 +1) valent aromatic hydrocarbon group. _ax1 is an integer of 1 or more. 2. The resist composition according to claim 1, wherein the cationic moiety of the ionic liquid (Z) is a cation represented by any one of the following general formulas (z-ca-1) to (z-ca-5):

[Wherein, Rz ^c1 ~Rz ^c6 are each independently an alkyl group having 1 to 12 carbon atoms. ^c7 ~Rz ^c9 Rz each independently represents an aryl group which may have a substituent. ^c10 ~Rz ^c13 are each independently a linear alkyl group having 1 to 20 carbon atoms. 2. The resist composition according to claim 1, wherein the anion moiety of the ionic liquid (Z) is an anion represented by any one of the following general formulas (z-an-1) to (z-an-5):

[In formula (z-an-1), Rz ^a1 represents an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain hydrocarbon group which may have a substituent. ^a2 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom, k is an integer of 1 to 4, l is an integer of 0 to 3, and k+l=4. ^a3 represents an alkyl group having 1 to 5 carbon atoms which may be substituted with a fluorine atom. m is an integer of 1 to 6, n is an integer of 0 to 5, and m+n=6. In formula (z-an-4), X" represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. In formula (z-an-5), Y" and Z" each independently represent an alkyl group having 1 to 10 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.] A method for forming a resist pattern, comprising the steps of forming a resist film on a support using the resist composition according to claim 1, exposing the resist film to light, and developing the exposed resist film to form a resist pattern.