TW202438487A - Sulfonium salt and acid generator containing said sulfonium salt - Google Patents

Abstract

The present invention provides a novel compound having the photosensitive property of rapidly decomposing to generate an acid when irradiated with light having a wavelength of less than 20 nm. The thiocyanate salt of the present invention is represented by the following formula (1). In the following formula, ^Rf1 and ^Rf2 are the same or different and represent a fluorine atom or a fluoroalkyl group. L is a group selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a carbonate bond, and a divalent group formed by linking at least one group selected from the above groups to a alkyl group. n1, n2, and n3 are the same or different and represent an integer of 1 to 5. ^X- represents a monovalent relative anion.

Description

Copper salt, and acid generator containing the above-mentioned copper salt

The present invention relates to a novel coronary art salt, an acid generator containing the coronary art salt, a photoresist containing the coronary art salt, and a method for manufacturing an electronic device using the photoresist.

Electronic devices are required to have larger capacity and smaller size. To achieve this, semiconductor integrated circuits must be made denser and more integrated.

As a method for making semiconductor integrated circuits high-density and high-integrated, photolithography is known. If photolithography is used, a fine pattern can be formed on a semiconductor. In photolithography, a chemically amplified resist including a photoacid generator and a resist is exposed, and the photoacid generator generates an acid. The generated acid changes the solubility of the resist in an alkaline developer, thereby forming a pattern. In addition, by shortening the wavelength of the exposure light, the pattern can be miniaturized.

Patent document 1 discloses that a resist containing triphenyl saponin as the above-mentioned photoacid generator can be processed with good precision by exposure using a KrF excimer laser or an ArF excimer laser. However, the above-mentioned resist has low sensitivity to light with a wavelength of less than 20 nm, such as EUV (extreme ultraviolet), EB (electron beam), and X-ray, and is difficult to be used in photolithography using the above-mentioned light.

Patent document 2 discloses that bis(3,5-difluorophenyl)phenylarsinium trifluoromethanesulfonate has high photosensitivity to EUV, EB, X-rays, etc. [Prior art document] [Patent document]

Patent document 1: Japanese Patent Publication No. 2011-191741 Patent document 2: Japanese Patent Publication No. 2017-8014

[The problem that the invention wants to solve]

However, the photosensitivity of bis(3,5-difluorophenyl)phenylarsinium trifluoromethanesulfonate to EUV, EB, X-rays, etc. is still insufficient, and an acid generator having further improved photosensitivity is desired.

Therefore, the object of the present invention is to provide a novel compound having photosensitivity of rapidly decomposing and generating acid when irradiated with light having a wavelength of less than 20 nm. Another object of the present invention is to provide a novel compound having the above-mentioned photosensitivity and excellent solvent solubility. Another object of the present invention is to provide an acid generator that efficiently generates acid by irradiation with light having a wavelength of less than 20 nm. Another object of the present invention is to provide a photoresist that can produce fine patterns with good precision by photolithography using light having a wavelength of less than 20 nm. Another object of the present invention is to provide a method for manufacturing an electronic device using the above-mentioned photoresist. [Technical means for solving the problem]

The inventors of the present invention have conducted in-depth research to solve the above problems and found that the cobalt salt represented by the following formula (1) has excellent sensitivity to light with a wavelength of less than 20 nm, and is easily decomposed to produce acid (H ⁺ X ^- ) (i.e., has excellent photosensitivity) when irradiated with light of the above wavelength, and has excellent solvent solubility. The present invention was completed based on these findings.

That is, the present invention provides a cobalt salt represented by the following formula (1). (In the formula, ^Rf1 and ^Rf2 are the same or different and represent a fluorine atom or a fluoroalkyl group. L is a group selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a carbonate bond, and a divalent group formed by linking at least one of the above groups to a alkyl group. n1, n2, and n3 are the same or different and represent an integer of 1 to 5. ^X- represents a monovalent relative anion)

Furthermore, the present invention provides the above-mentioned cobalt salt, wherein the above-mentioned monovalent relative anion is a sulfonate anion, a sulfonyl imide anion, or a halogen ion.

Furthermore, the present invention provides an acid generator comprising the above-mentioned cobalt salt.

Furthermore, the present invention provides the above-mentioned acid generator, which is an acid generator for extreme ultraviolet rays or an acid generator for electron beams.

Furthermore, the present invention provides a photoresist comprising the above-mentioned cobalt salt and an acid-reactive compound.

Furthermore, the present invention provides a method for manufacturing an electronic device, which includes the step of using the above-mentioned photoresist and forming a pattern by photolithography. [Effect of the invention]

The cobalt salt represented by the above formula (1) (hereinafter, sometimes referred to as "cobalt salt (1)") has excellent sensitivity to light with a wavelength of 20 nm or less, and can be easily decomposed to generate acid (H ⁺ X ^- ) by irradiation with light of the above wavelength. In addition, the above cobalt salt (1) has excellent solvent solubility, and when added to a photoresist, it can be evenly dispersed, giving the photoresist good fine pattern forming properties. Furthermore, when a photoresist containing the above cobalt salt (1) having the above characteristics is used to perform photolithography using light with a wavelength of 20 nm or less, a fine pattern can be formed with good precision, which can achieve further capacity expansion and further miniaturization of electronic devices.

[Copper Salt] The copper salt (1) of the present invention is a compound represented by the following formula (1) having a structure in which copper (H ₃ S ⁺ ) is substituted by two aromatic groups having a fluorine atom-containing group (fluorine atom or fluoroalkyl group) and one aromatic group having an iodinated aromatic group. (In the formula, ^Rf1 and ^Rf2 are the same or different and represent a fluorine atom or a fluoroalkyl group. L represents a linking group. The linking group is a group selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a carbonate bond, and a divalent group formed by linking at least one group selected from the above groups and a alkyl group. n1, n2, and n3 are the same or different and represent an integer of 1 to 5. ^X- represents a monovalent relative anion)

In addition, the symbols A, B, C, and D added to the benzene ring in the above formula are symbols added to distinguish the four benzene rings in the formula. Hereinafter, the benzene ring added with A is referred to as benzene ring A, the benzene ring added with B is referred to as benzene ring B, the benzene ring added with C is referred to as benzene ring C, and the benzene ring added with D is referred to as benzene ring D.

The fluoroalkyl group is a group in which at least one hydrogen atom of an alkyl group is replaced by a fluorine atom. The alkyl group is, for example, an alkyl group having 1 to 5 carbon atoms. In terms of easy availability of raw materials, an alkyl group having 1 to 3 carbon atoms is preferred, and an alkyl group having 1 or 2 carbon atoms is particularly preferred. The alkyl group includes, for example, a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and a pentyl group.

The fluoroalkyl group is preferably a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms, that is, a perfluoroalkyl group (e.g., a perfluoro C _1-5 alkyl group).

n1 and n2 represent integers of 1 to 5. In terms of significantly improving the acid generation rate by ultrashort wavelength light irradiation (i.e., improving the sensitivity to ultrashort wavelength light and easily decomposing and generating acid by ultrashort wavelength light irradiation), n1 and n2 are preferably integers of 1 to 3, particularly preferably 1 or 2, and most preferably 2.

n3 represents an integer of 1 to 5. In view of significantly improving the acid generation rate by ultrashort wavelength light irradiation, n3 is preferably an integer of 1 to 3, and particularly preferably 2 or 3.

The position at which the group represented by ^Rf1 in the above formula is bonded to the benzene ring A can be appropriately selected according to the number (n1) of the ^Rf1 groups. When n1=1, it is preferably the ortho position or the para position relative to the sulfur atom shown in formula (1). When n1=2, it is preferably the meta position relative to the sulfur atom shown in formula (1). When n1=3, it is preferably a combination of the ortho position and the para position, or a combination of the meta position and the para position relative to the sulfur atom shown in formula (1).

The position at which the group represented by ^Rf2 in the above formula is bonded to the benzene ring B can be appropriately selected according to the number (n2) of the ^Rf2 groups. When n2=1, it is preferably the ortho position or the para position relative to the sulfur atom shown in formula (1). When n2=2, it is preferably the meta position relative to the sulfur atom shown in formula (1). When n2=3, it is preferably a combination of the ortho position and the para position, or a combination of the meta position and the para position relative to the sulfur atom shown in formula (1).

The position where the group containing an iodinated aryl group in the above formula (i.e., the group containing a benzene ring D bonded to an iodine atom and a linking group L in the above formula) is bonded to the benzene ring C is preferably the meta position or the para position, and particularly preferably the para position.

The position where the iodine atom in the above formula is bonded to the benzene ring D can be appropriately selected according to the number of iodine atoms (n3). In terms of significantly improving the acid generation rate by ultrashort wavelength light irradiation, a compound having an iodine atom bonded at an adjacent position relative to the position where the linking group L is bonded is preferred.

That is, regarding the position where the iodine atom is bonded to the benzene ring D, when n3=1, it is preferably an adjacent position relative to the position where the linking group L is bonded. When n2=2, it is preferably an adjacent position, or an adjacent position and a meta position relative to the position where the linking group L is bonded. When n2=3, it is preferably a combination of an adjacent position and a meta position, or a combination of an adjacent position and a para position relative to the position where the linking group L is bonded.

As the above-mentioned cobalt salt (1), a compound represented by the following formula (1a) or a compound represented by the following formula (1b) is preferred in that the acid generation rate is significantly improved by irradiation with ultrashort wavelength light.

As the above-mentioned cobalt salt (1), a compound represented by the following formula (1c) is particularly preferred because the acid generation rate is significantly improved by irradiation with ultrashort wavelength light.

In the following formula, ^Rf1 , ^Rf2 , L, n1, n2, n3, and ^X- are the same as those described above. When there are plural ^Rf1 and ^Rf2 in the following formula, the plural ^Rf1 and ^Rf2 may be the same or different.

The above L is an ether bond (-O-), a carbonyl group (-CO-), an ester bond (-COO-), an amide bond (-CONH-), a carbonate bond (-OCOO-), or a divalent group formed by linking at least one group selected from the above groups to a hydrocarbon group.

The above-mentioned alkyl group is a divalent alkyl group, including a divalent aliphatic alkyl group, a divalent alicyclic alkyl group, a divalent aromatic alkyl group, and a divalent group formed by bonding thereof.

The alkyl group is preferably a divalent aliphatic alkyl group, and particularly preferably an alkylene group, since the acid generation rate is significantly increased by irradiation with ultrashort wavelength light.

The carbon number of the above alkyl group is preferably 1-5, particularly preferably 1-3.

The alkylene group is preferably a linear or branched alkylene group having 1 to 5 carbon atoms, such as methylene, methylmethylene, dimethylmethylene, ethylene, propylene, trimethylene, etc., and is particularly preferably a linear or branched alkylene group having 1 to 3 carbon atoms.

The above-mentioned alkyl group may be bonded to one or more substituents (e.g., hydroxyl, C _1-5 alkoxy, etc.).

As the above-mentioned L, in terms of significantly improving the acid generation rate by ultrashort wavelength light irradiation, it is preferably an ether bond, a carbonyl group, an ester bond, or a divalent group formed by linking at least one group selected from the above groups to a hydrocarbon group, and is particularly preferably an ether bond, an ester bond, or a divalent group formed by linking at least one group selected from the above groups to a hydrocarbon group.

It is preferred that one end of L bonded to C of the benzene ring has an ether bond or an ester bond. It is also preferred that the other end of L bonded to D of the benzene ring has an ether bond or an ester bond.

As the above-mentioned L, a group selected from the groups represented by the following formulae (L1) to (L5) is particularly preferred in that the acid generation rate is significantly improved by irradiation with ultrashort wavelength light. (In the above formula, R represents an alkyl group, and m represents 0 or 1. The left end of the above formula is bonded to C of the benzene ring, and the right end is bonded to D of the benzene ring)

The above R represents a alkyl group, and examples thereof include the same alkyl groups as those mentioned above for L. Preferred groups are also the same as those mentioned above for L.

The benzene ring A and the benzene ring B in the above formula each have a fluorine-containing group represented by ^Rf1 or ^Rf2 as a substituent. The benzene ring C has a group containing an iodinated aryl group as a substituent. The benzene ring D has an iodine atom as a substituent. The benzene rings A to D in the above formula may have other substituents in addition to the above groups. Examples of other substituents include: hydroxyl group, ^-Ra group, -OR ^group , -SR ^group , -COR ^group , etc. The above ^Ra represents a alkyl group, and examples include: _C1-5 alkyl group, _C2-5 alkenyl group, _C6-10 aryl group, etc.

In the case where the benzene rings A to D in the above formula of the cobalt salt (1) of the present invention have two or more other substituents, two of the substituents may be linked to each other to form a ring together with the carbon atom to which the substituents are bonded (the carbon atom constituting the above benzene ring).

Examples of substituents of the cobalt salt (1) forming a ring include compounds represented by the following formula (1') and compounds represented by the following formula (1"). In the following formulas, ^Rf1 , Rf2, L, n1, ⁿ² , n3, and ^X- are the same as those described above.

In the above formula (1'), ^R1 represents a single bond, -O-, -NH-, -S-, -SO-, _-SO2- , -CO-, or a _C1-5 alkylene group.

The ring Z in the above formula (1") is a ring condensed with the benzene ring A, and examples thereof include: a C _3-6 aliphatic hydrocarbon ring such as a cyclohexane ring; a C _6-12 aromatic hydrocarbon ring such as a benzene ring and a naphthalene ring; a 3-6 membered non-aromatic heterocyclic ring containing an oxygen atom, a sulfur atom, or a nitrogen atom as a heteroatom; and a 3-6 membered aromatic heterocyclic ring containing an oxygen atom, a sulfur atom, or a nitrogen atom as a heteroatom.

In the above formula, ^X- represents a monovalent relative anion, for example, a halogen ion, a halogen oxo acid anion, a boron anion, a phosphate anion, a sulfate anion, a sulfonate anion, a sulfonylimide anion, a carboxylate anion, a gallate anion, a methide anion, an antimony anion, ^OH- , _{SCN-, NO2-} ^{, NO3-} _, ^etc.

Examples of the halogen ions include Cl ^- , Br ^- , and I ^- .

Examples of the halogen oxyacid anions include ClO ₄ ^- , IO ₃ ^- , and BrO ₃ ^- .

Examples of the boron anion include inorganic boron anions such as BF ₄ ^- and organic boron anions such as (C ₆ F ₅ ) ₄ B ^- , ((CF ₃ ) ₂ C ₆ H ₃ ) ₄ B ^- , tetraphenylborate, tetrakis(monofluorophenyl)borate, tetrakis(difluorophenyl)borate, and tetrakis(trifluorophenyl)borate.

Examples of the phosphate anions include inorganic phosphate anions such as _PF6- , _PF ( _{C2F5 ) 5-} ^, _PF2 ( _C2F5 ) _{4- , PF3} ⁽ _{C2F5 )} ^3- _{, PF4} ( _C2F5 ^)2- _{, PF5 ( C2F5} ) ^{- ,} and _PO43- ^.

The sulfonate anion is represented by, for example, the following formula (s1): R ^s1 -SO ₃ ^- (s1) (wherein R ^s1 represents an organic group)

Examples of the organic group of R ^s1 include: a C _1-30 alkyl group which may have a substituent, a heterocyclic group which may have a substituent, a group in which two or more of the above groups are bonded via a single bond, or a group in which two or more of the above groups are bonded via a linking group selected from -O-, -CO ₂ -, -S-, -SO ₃ -, and -SO ₂ N(R ^s2 )-. In addition, the above groups may also be bonded to the following acid-reactive compound (or a monomer constituting the following acid-reactive compound). That is, the anionic part constituting the above polymerizable compound (1) may contain the following acid-reactive compound (or a monomer constituting the following acid-reactive compound) in its structure.

The above R ^s2 represents a hydrogen atom or an alkyl group (eg, a C _1-30 alkyl group).

Examples of the substituent include halogen atoms such as a fluorine atom.

The above-mentioned C _1-30 alkyl group includes a C _1-30 aliphatic alkyl group, a C _3-30 alicyclic alkyl group, a C _6-30 aromatic alkyl group, and a group formed by two bonds of the same.

The C _1-30 alkyl group is preferably a C _1-30 alkyl group, a C _6-15 aryl group, a C _6-15 cycloalkylene group, a C _6-15 bridged cyclic alkyl group, or a group formed by two bonds of the same.

The heterocyclic group is a group obtained by removing one hydrogen atom from the structural formula of a heterocyclic ring. The heterocyclic ring includes an aromatic heterocyclic ring and a non-aromatic heterocyclic ring. Examples of such heterocyclic rings include 3-10 membered rings (preferably 4-6 membered rings) having carbon atoms and at least one hetero atom (e.g., oxygen atoms, sulfur atoms, nitrogen atoms, etc.) on the atoms constituting the ring, and condensed rings thereof.

Specific examples of the sulfonate anion include CH ₃ SO ₃ ^- (MsO ^- ), C ₄ H ₉ SO ₃ ^- , CF ₃ SO ₃ ^- , C ₂ F ₅ C ₄ H ₄ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , benzenesulfonate anion, p-toluenesulfonate anion, and camphorsulfonate anion.

The sulfonyl imide anion is represented by, for example, the following formula (n1): (R ⁿ¹ SO ₂ ) ₂ N ^- (n1) (wherein, two R ^n1s are the same or different and represent an organic group)

As the organic group for R ⁿ¹ , the same organic groups as those for R ^s1 can be exemplified.

Specific examples of the sulfonyl imide anion include (FSO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (C ₄ F ₉ SO ₂ ) ₂ N ^- , and (C ₂ F ₅ SO ₂ ) ₂ N ^- .

The carboxylate anion is represented by, for example, the following formula (c1): R ^c1 -COO ^- (c1) (wherein R ^c1 represents an organic group)

As the organic group for R ^c1 , the same organic groups as those for R ^s1 can be exemplified.

Specific examples of the carboxylate anion include CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , C ₂ H ₅ CO ₂ ^- , and PhCO ₂ ^- .

The gallate anion is represented by the following formula (g1), for example. (R ^g1 ) _t (F) _4-t Ga ^- (g1) (wherein R ^g1 represents a fluoroalkyl group, a fluoroaryl group, or an aryl group substituted with a fluoroalkyl group, and t represents an integer of 1 to 4)

The fluoroalkyl group of ^Rg1 is a group in which at least one hydrogen atom bonded to an alkyl group is substituted by a fluorine atom, wherein a perfluoroalkyl group is preferred, a perfluoro _C1-5 alkyl group is particularly preferred, and a perfluoro _C1-3 alkyl group is most preferred.

The fluoroaryl group of ^Rg1 is a group in which at least one hydrogen atom bonded to an aryl group is replaced by a fluorine atom. As the above-mentioned aryl group, for example, phenyl, naphthyl and other aryl groups having 6 to 14 carbon atoms are preferred, and phenyl is particularly preferred.

The fluoroaryl group for ^Rg1 is preferably a perfluoroaryl group, particularly preferably a perfluoro _C6-14 aryl group, and most preferably a perfluorophenyl group.

The aryl group substituted with a fluoroalkyl group for ^Rg1 is an aryl group having as a substituent a group in which at least one hydrogen atom bonded to the alkyl group is substituted with a fluorine atom.

The aryl group substituted by a fluoroalkyl group for ^Rg1 is preferably an aryl group substituted by a perfluoroalkyl group, more preferably an aryl group substituted by a perfluoro _C1-5 alkyl group, and particularly preferably a _C6-14 phenyl group substituted by a perfluoro _C1-3 alkyl group.

The number of fluoroalkyl groups in the aryl group substituted with a fluoroalkyl group represented by R ^g1 is, for example, 1 to 5, preferably 1 to 3, and particularly preferably 1 or 2.

In formula (g1), t represents an integer of 1 to 4, preferably an integer of 2 to 4, particularly preferably 3 or 4, and most preferably 4.

Examples of the gallate anion include tetrafluorogallate anion, tetrakis(pentafluorophenyl)gallate anion, tetrakis(4-fluorophenyl)gallate anion and the like, tetrakis(difluorophenyl)gallate anion and the like, tris(pentafluorophenyl)fluorogallate anion, bis(pentafluorophenyl)difluorogallate anion, (pentafluorophenyl)trifluorogallate anion, tetrakis[4-(trifluoromethyl)phenyl]gallate anion and the like, and tetrakis[(C- [(C _1-5 halogen alkyl) phenyl] gallate anion; tetrakis[3,5-bis(trifluoromethyl)phenyl] gallate anion, tetrakis[bis(C _1-5 halogen alkyl)phenyl] gallate anion; bis[4-(trifluoromethyl)phenyl] fluorogallate anion, bis[(C _1-5 halogen alkyl)phenyl] fluorogallate anion, etc.; bis[3,5-bis(trifluoromethyl)phenyl] fluorogallate anion, bis[bis(C _1-5 halogen alkyl)phenyl] fluorogallate anion, etc.; bis[4-(trifluoromethyl)phenyl] difluorogallate anion, bis[(C 1-5 halogen alkyl)phenyl] fluorogallate anion, etc. [( _{C 1-5} halogenalkyl)phenyl] trifluorogallate anion; bis[3,5-bis(trifluoromethyl)phenyl]difluorogallate anion and the like bis[bis(C _1-5 halogenalkyl)phenyl]difluorogallate anion; [4-(trifluoromethyl)phenyl]trifluorogallate anion and the like [(C _1-5 halogenalkyl)phenyl]trifluorogallate anion; [3,5-bis(trifluoromethyl)phenyl]trifluorogallate anion and the like [bis(C _1-5 halogenalkyl)phenyl]trifluorogallate anion and the like.

Examples of the methide anion include sulfonyl methide anions represented by the following formula (m1): (R ^m1 SO ₂ ) ₃ C ^- (m1) (wherein, three R ^m1s are the same or different and represent an organic group)

As the organic group for R ^m1 , the same organic groups as those for R ^s1 can be exemplified.

Specific examples of the methylated anion include (CF ₃ SO ₂ ) ₃ C ^- and the like.

Examples of the antimony anion include SbF ₆ ^- and the like.

In addition to the above, the monovalent relative anions include, for example, anions described in Japanese Patent Application Laid-Open No. 2013-47211, Japanese Patent Application Laid-Open No. 2021-81708, Japanese Patent Application Laid-Open No. 2013-80245, Japanese Patent Application Laid-Open No. 2013-80240, and Japanese Patent Application Laid-Open No. 2013-33161.

As the above-mentioned relative anion, in terms of improving the sensitivity to ultrashort wavelength light and excellent solvent solubility, preferably, it is a sulfonate anion, a sulfonylimide anion, or a halogen ion, and particularly preferably, it is a sulfonate anion or a sulfonylimide anion.

The above-mentioned cobalt salt (1) has excellent solubility in organic solvents. Its solubility in organic solvents (e.g., propylene glycol monomethyl ether acetate (PGMEA)) at 25° C. is, for example, 2% by weight or more (e.g., 2 to 50% by weight), preferably 3% by weight or more, further preferably 4% by weight or more, and particularly preferably 5% by weight or more.

Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; carbonates such as propyl carbonate, ethyl carbonate, 1,2-butyl carbonate, dimethyl carbonate, and diethyl carbonate; chain or cyclic esters such as ethyl acetate, butyl acetate, and ethyl lactate; β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone; ethylene glycol monomethyl ether; , propylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, triethylene glycol diethyl ether, tripropylene glycol dibutyl ether and other glycol diethers; ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate and other glycol monoether monoesters; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl isoamyl ketone, 2-heptanone and other ketones. These can be used alone or in combination of two or more.

The organic solvent preferably contains at least one selected from ketones, chain esters, and glycol monoether monoesters.

The above-mentioned stibnium salt (1) has a high sensitivity to light with a wavelength of less than 20 nm, such as EUV (extreme ultraviolet), EB (electron beam), and X-ray. Moreover, even without using a photosensitizer, the light energy is directly transmitted to the stibnium salt (1) by irradiating light of the above-mentioned wavelength, and it is rapidly photodecomposed to generate acid (H ⁺ X ^- : X ^- is the same as above).

Since the above-mentioned cobalt salt (1) has the above-mentioned properties, it can be suitably used as an acid generator (for example, a photoacid generator).

An example of a method for producing the above-mentioned cobalt salt (1) is described below. The compound represented by the following formula (1-1) in the above-mentioned cobalt salt (1) can be produced, for example, through the following steps [I] and [II].

In the above formula, ^Rf1 , ^Rf2 , L, n1, n2, n3 and X- are the same as those described above. X ^' represents a halogen atom.

The above step [I] is a step of subjecting a compound represented by formula (I) (i.e., compound (I)) to dehydration condensation with a compound represented by formula (II) (i.e., compound (II)), and then reacting with a relative anion source that generates ^X- to obtain a compound represented by formula (III) (i.e., compound (III)).

The anion source can be selected according to X ^- . When X ^- is, for example, CF ₃ SO ₃ ^- , methanesulfonic acid, trifluoromethanesulfonic acid, or anhydride thereof can be used as the relative anion source.

The molar ratio of compound (I) to compound (II) (compound (I)/compound (II)) used in the above reaction is, for example, 1/3 to 3/1, preferably 1/2 to 2/1.

The relative usage amount of the anion source is, for example, 1.0 to 10.0 mol, preferably 1.0 to 2.0 mol, relative to 1 mol of compound (I).

The above reaction is preferably carried out in the presence of a dehydrating agent. Examples of the dehydrating agent include phosphorus pentoxide, polyphosphoric acid, concentrated sulfuric acid, phosphoric anhydride, methanesulfonic acid, trifluoromethanesulfonic acid or its anhydride, etc. These can be used alone or in combination of two or more.

The above step [II] is a step of reacting compound (III) with a compound represented by formula (IV) (i.e., compound (IV)) to obtain a compound represented by formula (1-1).

The molar ratio of compound (III) to compound (IV) (compound (III)/compound (IV)) used in the above reaction is, for example, 1/3 to 3/1, preferably 1/2 to 2/1.

The above reaction is preferably carried out in the presence of a base such as triethylamine.

The above reaction can be carried out in the presence of a solvent. As the above solvent, for example, one or more solvents selected from acetonitrile, ethyl acetate, tetrahydrofuran, chloroform, dichloromethane and the like can be used.

The reaction temperature is, for example, about -20 to 80°C.

The environment of the reaction is not particularly limited as long as it does not hinder the reaction, and may be, for example, an air environment, a nitrogen environment, an argon environment, etc. The reaction may also be carried out by any method such as a batch method, a semi-batch method, or a continuous method.

After the above reaction is completed, the obtained reaction product can be separated and purified by separation means such as filtration, concentration, distillation, extraction, crystallization, adsorption, recrystallization, column chromatography, or a combination of these separation means.

The chemical structure of the cobalt salt of the present invention can be identified by, for example, ¹ H-, ¹¹ B-, ¹³ C-, ¹⁹ F-, or ³¹ P-nuclear magnetic resonance spectroscopy, infrared absorption spectroscopy, mass spectrometry, or elemental analysis.

[Acid Generator] The acid generator of the present invention contains at least the above-mentioned cobalt salt (1). The above-mentioned acid generator may contain one kind of the above-mentioned cobalt salt (1) alone, or may contain two or more kinds in combination. In addition, the above-mentioned acid generator may also contain components other than the above-mentioned cobalt salt (1), wherein the ratio of the above-mentioned cobalt salt (1) to all compounds (100% by weight) contained in the above-mentioned acid generator that generate acid by decomposition under light irradiation is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, and particularly preferably 95% by weight or more.

That is, the acid generator may also contain acid generators other than the cobalt salt (1), wherein the content of the other acid generators relative to all compounds (100% by weight) contained in the acid generator that generate acids by decomposition upon light irradiation is, for example, preferably 50% by weight or less, more preferably 40% by weight or less, further preferably 30% by weight or less, particularly preferably 20% by weight or less, most preferably 10% by weight or less, and particularly preferably 5% by weight or less.

The acid generator has excellent solubility in an organic solvent. The amount of the acid generator (or the cobalt salt (1)) dissolved in 100 parts by weight of the organic solvent at 25° C. is, for example, 2 parts by weight or more, preferably 3 parts by weight or more, particularly preferably 4 parts by weight or more, and most preferably 5 parts by weight or more. As the organic solvent, the same organic solvents as those in which the cobalt salt (1) is soluble can be cited (e.g., PGMEA, etc.).

The above acid generator is not only highly sensitive to light with a wavelength longer than 20 nm, but also highly sensitive to light with a wavelength below 20 nm (such as EUV, EB, X-rays, etc.). When irradiated with the above light, it is easily decomposed to generate acid (H ^{+ X-} ; ^X- is equivalent to ^X- in formula (1)).

The acid generation rate of the acid generator (for example, the acid generation rate determined by the method described in the examples) is, for example, 40% or more, preferably 50% or more.

Since the acid generator has the above-mentioned characteristics, it can be suitably used as an acid generator for photoresists (especially acid generators for photoresists used in photolithography using light with a wavelength of less than 20 nm).

[Photoresist] The photoresist of the present invention comprises the above-mentioned acid generator (or the above-mentioned cobalt salt (1)) and an acid-reactive compound.

The content of the acid generator (or the cobalt salt (1)) is, for example, 0.001 to 20% by weight, preferably 0.01 to 15% by weight, and particularly preferably 0.05 to 7% by weight, of the acid-reactive compound contained in the photoresist (the total amount when two or more types are contained).

If the content of the acid generator (or the cobalt salt (1)) is 0.001% by weight or more of the content of the acid-reactive compound, the photoresist can exhibit excellent sensitivity not only to light with a wavelength longer than 20 nm, but also to light with a wavelength below 20 nm. Furthermore, if the content of the acid generator (or the cobalt salt (1)) is 20% by weight or less of the content of the acid-reactive compound, the resolution of the photoresist can be improved.

The acid-reactive compound is a compound whose solubility in an alkaline developer changes due to the action of an acid. The photoresist of the present invention may contain one of the acid-reactive compounds alone or in combination of two or more.

The acid-reactive compound includes the following compounds: compounds that are easily soluble in an alkaline developer and react with a crosslinking agent in the presence of an acid to generate compounds that are poorly soluble or insoluble in an alkaline developer; and compounds that are poorly soluble or insoluble in an alkaline developer and whose solubility in an alkaline developer is increased by the action of an acid.

Therefore, the above-mentioned photoresist includes the following composition (1) and composition (2). Composition (1): A composition including the above-mentioned acid generator and a negative photosensitive resin (QN) that is easily soluble in an alkaline developer and generates a compound that is poorly soluble or insoluble in an alkaline developer in the presence of an acid Composition (2): A composition including the above-mentioned acid generator and a positive photosensitive resin (QP) that is poorly soluble or insoluble in an alkaline developer and whose solubility in an alkaline developer is increased by the action of an acid

Examples of the negative photosensitive resin (or negative chemically amplified resin; QN) include a composition containing a phenolic hydroxyl group-containing resin (QN1) and a crosslinking agent (QN2).

The phenolic hydroxyl group-containing resin (QN1) is a phenolic hydroxyl group-containing resin that is easily soluble in an alkaline developer and that reacts with a crosslinking agent to become poorly soluble or insoluble in an alkaline developer, and examples thereof include novolac resins, polyhydroxystyrene, copolymers of hydroxystyrene, copolymers of hydroxystyrene and styrene, copolymers of hydroxystyrene, styrene and (meth)acrylic acid derivatives, phenol-xylylene glycol condensation resins, cresol-xylylene glycol condensation resins, polyimide containing a phenolic hydroxyl group, polyamide containing a phenolic hydroxyl group, phenol-dicyclopentadiene condensation resins, etc. These resins may be used alone or in combination of two or more.

The phenolic hydroxyl-containing resin (QN1) may contain a phenolic low molecular weight compound as part of its composition.

The polystyrene-equivalent weight average molecular weight (Mw) of the phenolic hydroxyl group-containing resin (QN1) measured by GPC is, for example, 2,000 to 20,000.

The crosslinking agent (QN2) is, for example, a compound that can crosslink the phenolic hydroxyl-containing resin (QN1) by an acid generated by a self-acid generator, and examples thereof include: bisphenol A-based epoxy compounds, bisphenol F-based epoxy compounds, bisphenol S-based epoxy compounds, novolac-based epoxy compounds, resol-based epoxy compounds, poly(hydroxystyrene)-based epoxy compounds, cyclohexane compounds, hydroxymethyl-containing melamine compounds, hydroxymethyl-containing benzoguanamine compounds, hydroxymethyl-containing urea compounds containing alkyl groups, hydroxymethyl-containing phenol compounds, alkoxyalkyl-containing melamine compounds, alkoxyalkyl-containing benzoguanamine compounds, alkoxyalkyl-containing urea compounds, alkoxyalkyl-containing phenol compounds, carboxymethyl-containing melamine resins, carboxymethyl-containing benzoguanamine resins, carboxymethyl-containing urea resins, carboxymethyl-containing phenol resins, carboxymethyl-containing melamine compounds, carboxymethyl-containing benzoguanamine compounds, carboxymethyl-containing urea compounds, and carboxymethyl-containing phenol compounds. These may be used alone or in combination of two or more.

From the viewpoint of efficiently making the phenolic hydroxyl-containing resin (QN1) difficult to dissolve or insoluble in an alkaline developer, the content of the crosslinking agent (QN2) is, for example, 10 to 40 mol % relative to all the acidic functional groups in the phenolic hydroxyl-containing resin (QN1).

Examples of the positive photosensitive resin (or positive chemically amplified resin; QP) include an alkali-soluble resin into which an acid-dissociable group is introduced as a protecting group (protecting group-introduced resin; QP1).

The protective group-introduced resin (QP1) is a resin in which part or all of the hydrogen atoms of the acidic functional groups (such as phenolic hydroxyl, carboxyl, sulfonyl, etc.) in the alkali-soluble resin are replaced by acid-dissociable groups.

The protecting group-introduced resin (QP1) itself is a resin that is insoluble or poorly soluble in an alkaline developer. When the acid-dissociable group is dissociated by the acid (H ⁺ X ^- ) generated by the self-acid generator, it becomes an alkali-soluble resin that is easily soluble in an alkaline developer.

The alkali-soluble resin is, for example, a resin having an HLB value of 4 to 19 (preferably 5 to 18, particularly preferably 6 to 17).

Alkaline-soluble resins include resins containing phenolic hydroxyl groups, resins containing carboxyl groups, and resins containing sulfonic acid groups.

Examples of the phenolic hydroxyl group-containing resin include the same resins as those described above for the phenolic hydroxyl group-containing resin (QN1).

The carboxyl group-containing resin is not particularly limited as long as it is a polymer having a carboxyl group, and examples thereof include a homopolymer of a carboxyl group-containing vinyl monomer (Ba) or a homopolymer of a carboxyl group-containing vinyl monomer (Ba) and a hydrophobic group-containing vinyl monomer (Bb).

The carboxyl group-containing vinyl monomer (Ba) is, for example, (meth)acrylic acid.

Examples of the hydrophobic group-containing vinyl monomer (Bb) include (meth)acrylates (Bb1) such as C _1-20 alkyl (meth)acrylates and (meth)acrylates containing alicyclic groups, and hydrocarbon monomers having a styrene skeleton or aromatic hydrocarbon monomers such as vinylnaphthalene (Bb2).

The sulfonic acid group-containing resin is not particularly limited as long as it is a polymer having a sulfonic acid group, and can be obtained, for example, by vinyl polymerization of a sulfonic acid group-containing vinyl monomer (Bc) such as vinyl sulfonic acid and styrene sulfonic acid and, if necessary, a hydrophobic group-containing vinyl monomer (Bb).

Examples of the acid-dissociable groups introduced as the protecting groups into the resin (QP1) include 1-substituted methyl groups such as methoxymethyl, benzyl, and tert-butoxycarbonylmethyl; 1-substituted ethyl groups such as 1-methoxyethyl and 1-ethoxyethyl; 1-branched alkyl groups such as tert-butyl; silyl groups such as trimethylsilyl; germanium groups such as trimethylgermyl; alkoxycarbonyl groups such as tert-butoxycarbonyl; acyl groups; cyclic acid-dissociable groups such as tetrahydropyranyl, tetrahydrofuranyl, tetrahydrothiopyranyl, and tetrahydrothienyl. These groups may be contained alone or in combination of two or more.

The introduction rate of the acid-lysable group into the resin (QP1) by the protective group {the ratio of the number of acid-lysable groups to the total number of unprotected acidic functional groups and acid-lysable groups in the resin (QP1) introduced by the protective group} cannot be generally determined by the type of the acid-lysable group or the alkali-soluble resin into which the group is introduced, but is preferably 10 to 100%, and more preferably 15 to 100%.

The polystyrene-equivalent weight average molecular weight (Mw) of the protecting group-introduced resin (QP1) measured by GPC is, for example, 1,000 to 150,000, preferably 3,000 to 100,000.

The photoresist of the present invention can be prepared, for example, by dissolving the acid generator (or the cobalt salt (1)) in an organic solvent and mixing the organic solvent with a photosensitive resin.

The photoresist of the present invention may contain one or more other components as required in addition to the above-mentioned acid generator (or the above-mentioned cobalt salt (1)) and the photosensitive resin. Examples of other components include organic solvents, pigments, dyes, photosensitizers, dispersants, surfactants, fillers, leveling agents, defoamers, antistatic agents, ultraviolet absorbers, pH adjusters, surface modifiers, plasticizers, drying accelerators, etc.

As the above-mentioned organic solvent, any solvent that can dissolve the above-mentioned photosensitive resin and give good coating properties to the photoresist can be used. Among them, from the perspective of being able to easily dry the photoresist after coating, it is preferred to use a solvent with a boiling point of 200°C or less. As such an organic solvent, preferably: aromatic hydrocarbons such as toluene; alcohols such as ethanol and methanol; ketones such as cyclohexanone, methyl ethyl ketone, and acetone; esters such as ethyl acetate, butyl acetate, and ethyl lactate; glycol monoether monoesters such as propylene glycol monomethyl ether acetate (PGMEA), etc. These can be used alone or in combination of two or more.

The photoresist of the present invention contains a cobalt salt (1) having a high sensitivity to light with a wavelength of less than 20 nm. Therefore, even when irradiated with light with a wavelength of less than 20 nm, even if no photosensitizer is contained, acid (H ⁺ X ^- ) can be efficiently generated in the exposed part. Moreover, due to the generated acid (H ⁺ X ^- ), the solubility of the photosensitive resin in the exposed part in the developer changes. When the above-mentioned photosensitive resin is a negative photosensitive resin, the solubility decreases due to irradiation. On the other hand, when the above-mentioned photosensitive resin is a positive photosensitive resin, the solubility increases due to irradiation. Therefore, if the photoresist of the present invention is used, an etching mask can be formed with good precision by photolithography.

[Manufacturing method of electronic device] The manufacturing method of the electronic device of the present invention includes the step of using the above-mentioned photoresist and forming a pattern by photolithography.

The step of using the above-mentioned photoresist and performing pattern formation by photolithography is preferably a step of forming an etching mask on the substrate through the following steps 1 to 3.

Step 1: Forming a coating of the photoresist on a substrate Step 2: Irradiating the coating with light in a pattern shape Step 3: Performing alkaline development

(Step 1) This step is to form a coating of the photoresist on the etched substrate. The photoresist coating can be formed by applying the photoresist on the substrate using a known method such as spin coating, curtain coating, roll coating, spray coating, screen printing, etc., and then drying it.

(Step 2) This step is to irradiate the coating obtained in step 1 with light in a patterned shape by using a photomask having a pattern as an intermediary. The light used for the light irradiation is not particularly limited as long as it can decompose the above-mentioned cobalt salt (1) to produce a strong acid. Not only light with a wavelength longer than 20 nm can be suitably used, but also light with a wavelength below 20 nm such as EUV (extreme ultraviolet), EB (electron beam), and X-ray can be suitably used.

In order to increase the difference in solubility between the exposed portion and the unexposed portion in the alkaline developer, it is preferred to heat at a temperature of 60 to 200° C. for about 0.1 to 120 minutes after light irradiation.

(Step 3) This step is to apply alkaline development treatment to the photoresist coating film after step 2.

Examples of the alkaline developer used in the alkaline development treatment include an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, sodium bicarbonate, and an aqueous tetramethylammonium salt solution.

Methanol, ethanol, isopropyl alcohol, tetrahydrofuran, N-methylpyrrolidone, etc. may also be added to the alkaline developer.

The alkaline development treatment is performed by applying the alkaline developer to the coating film by a dipping method, a spraying method, a misting method or the like.

The temperature of the alkaline developer is, for example, 25 to 40° C. The alkaline development time is appropriately determined according to the thickness of the photoresist, for example, about 1 to 5 minutes.

After step 3, an etching mask can be formed on the substrate. If the substrate is etched using the etching mask obtained in this way, a high-precision electronic device can be manufactured.

The electronic devices include, for example, display devices such as organic EL displays and liquid crystal displays; input devices such as touch panels; light-emitting devices; sensor devices; MEMS (Micro Electro Mechanical Systems) devices such as optical scanners, optical switches, accelerometers, pressure sensors, rotors, microchannels, and inkjet heads.

The above-mentioned components and their combinations are examples, and the components can be appropriately added, omitted, replaced, and changed without departing from the main purpose of the present invention. In addition, the present invention is not limited by the implementation method, but only by the description of the scope of the patent application. [Implementation Example]

Hereinafter, the present invention will be described in more detail by way of embodiments, but the present invention is not limited to these embodiments.

Preparation Example 1 (Preparation of Compound (I-1)) To a tetrahydrofuran solution of 3,5-difluorophenylmagnesium bromide prepared by a conventional method using 96.5 g of 1-bromo-3,5-difluorobenzene, 13.4 g of magnesium, and 400 g of tetrahydrofuran, a solution prepared by diluting 28.6 g of sulfinyl chloride with 50 g of tetrahydrofuran was added dropwise at a rate such that the temperature in the system did not exceed -5°C. After the addition was completed, the reaction was continued at room temperature for 1 hour to terminate the reaction. The solution after the above reaction was added to 500 g of ion-exchanged water at a rate such that the temperature in the system did not exceed 15°C, and stirred for 1 hour. Thereafter, 300 g of ethyl acetate was added, and after stirring for 1 hour, the aqueous layer was removed. Afterwards, the mixture was washed with 300 g of ion-exchanged water, and the water layer was removed three times. Afterwards, the solvent was removed, and the obtained brown residue was recrystallized with cyclohexane to obtain 26.0 g of bis(3,5-difluorophenyl)sulfoxide.

(Preparation of compound (III-1)) 26.0 g of the obtained bis(3,5-difluorophenyl)sulfoxide and 20.8 g of dimethylphenol were dissolved in 71 g of trifluoromethanesulfonic acid. Then, the mixture was cooled to below 5°C and 29.4 g of trifluoromethanesulfonic anhydride was added in small amounts over 2 hours. Then, the reaction was continued at room temperature for 12 hours to terminate the reaction. Then, 500 g of ion exchange water was added and stirred for 1 hour, and then 300 g of toluene was added and stirred for another 1 hour, and then the organic layer was removed. 100 g of toluene was added to the remaining water layer for washing, and the washing operation of removing the organic layer was performed 3 times. Thereafter, the aqueous layer was filtered to recover the precipitate, which was then dried under reduced pressure. Thus, 37.6 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate was obtained.

Preparation Example 2 Bis(3,5-difluorophenyl)sulfoxide was obtained by the same method as in Preparation Example 1 (Preparation of Compound (I-1)).

Dissolve 26.0 g of the obtained bis(3,5-difluorophenyl)sulfoxide and 20.8 g of dimethylphenol in 46 g of methanesulfonic acid. Then, cool to below 5°C, and add 14.8 g of phosphorus pentoxide in small amounts over 2 hours. Then, continue the reaction at room temperature for 12 hours to terminate the reaction. Then, add 500 g of ion exchange water and stir for 1 hour. Then, add 300 g of ethyl acetate and stir for 1 hour, and then remove the organic layer. Add 100 g of ethyl acetate to the remaining water layer for washing, and perform the washing operation of removing the organic layer 3 times. Then, 300 g of dichloromethane was added and stirred for 1 hour, the aqueous layer was removed, and the dichloromethane was distilled off under reduced pressure. Thus, 33.7 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic methanesulfonate was obtained.

Preparation Example 3 Bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate was obtained by the same method as Preparation Example 1.

37.6 g of the obtained bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)copperium trifluoromethanesulfonate was dissolved in 182 g of methanol, 29.5 g of potassium carbonate was added, and 17.2 g of 2-chloroethanol was added in small amounts at room temperature for 1 hour. Thereafter, the reaction was continued at room temperature for 12 hours to terminate the reaction. Then, 250 g of ion exchange water was added and stirred for 1 hour, and then 300 g of dichloromethane was added and stirred for 1 hour, and the water layer was removed. 250 g of ion exchange water was added to the remaining organic layer for washing, and the washing operation of removing the water layer was performed 3 times. Thereafter, dichloromethane was distilled off under reduced pressure. Thus, 27.1 g of [bis(3,5-difluorophenyl)][4-(2-hydroxyethoxy)-3,5-dimethylphenyl]arsenic trifluoromethanesulfonate was obtained.

Preparation Example 4 [Bis(3,5-difluorophenyl)][4-(2-hydroxyethoxy)-3,5-dimethylphenyl]arsenic trifluoromethanesulfonate was obtained by the same method as Preparation Example 3.

27.1 g of the obtained [bis(3,5-difluorophenyl)][4-(2-hydroxyethoxy)-3,5-dimethylphenyl]copperium trifluoromethanesulfonate was added to 136 g of dichloromethane, cooled to below 5°C, and then 25.2 g of triphenylphosphine and 17.1 g of N-bromobutanediimide were added and stirred for 12 hours. Then, 200 g of ion-exchanged water was added and stirred for 1 hour, and then the water layer was removed. 200 g of ion-exchanged water was added to the remaining organic layer for washing, and the washing operation of removing the water layer was performed 3 times. Thereafter, dichloromethane was distilled off under reduced pressure. In this way, 28.5 g of [bis(3,5-difluorophenyl)][4-(2-bromoethoxy)-3,5-dimethylphenyl]arsenic trifluoromethanesulfonate was obtained.

Example 1 37.6 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate obtained in Preparation Example 1 and 43.2 g of triethylamine were added to 121 g of dichloromethane. Then, the mixture was cooled to below 5°C and 20.9 g of 2-iodobenzoic acid chloride was added in small amounts over 2 hours. Then, the reaction was continued at room temperature for 1 hour to terminate the reaction. Then, 200 g of ion exchange water was added and stirred for 1 hour, and then 100 g of toluene was added and stirred for another 1 hour, and the precipitate was filtered out. The precipitate was washed with tert-butyl methyl ether and dried under reduced pressure. Thus, 37.8 g of the zinc salt (1a) which is a salt of cations and anions as shown in the following table was obtained. This was used as an acid generator (1).

Example 2 33.7 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic methanesulfonate obtained in Preparation Example 2 and 43.1 g of triethylamine were added to 121 g of dichloromethane. Then, the mixture was cooled to below 5°C and 20.8 g of 2-iodobenzyl chloride was added in small amounts over 2 hours. Then, the reaction was continued at room temperature for 1 hour to terminate the reaction. Then, 200 g of ion exchange water was added and stirred for 1 hour, and then 100 g of toluene was added and stirred for another 1 hour, and the precipitate was filtered out. After the obtained precipitate was added to 120 g of dichloromethane, 100 g of a saturated sodium bromide aqueous solution was added and stirred for 1 hour, and the aqueous layer was removed. Thereafter, 100 g of ion exchange water was added to the remaining organic layer for washing, and the washing operation of removing the aqueous layer was performed three times. Thereafter, the dichloromethane was distilled off under reduced pressure, and the obtained solid was washed with tert-butyl methyl ether and dried under reduced pressure. Thus, 46.8 g of the iron salt (1b) as a salt of the cation and anion described in the following table was obtained. It was used as an acid generator (2).

Example 3 Except that 40.6 g of 2,3,5-triiodobenzyl chloride was used instead of 20.8 g of 2-iodobenzyl chloride, 50.3 g of the cobalt salt (1c) as the salt of the cation and anion shown in the following table was obtained in the same manner as in Example 1. This was used as an acid generator (3).

Example 4 50.3 g of cobalt salt (1c) synthesized by the same method as in Example 3 and 423 g of dichloromethane were mixed in 370 g of a 5% potassium nonafluorobutanesulfonate aqueous solution and stirred at 25°C for 2 hours. Thereafter, the aqueous layer was removed, and the remaining organic layer was washed several times with 200 g of ion-exchanged water and dried under reduced pressure. Thus, 52.0 g of cobalt salt (1d) as a salt of cations and anions as shown in the following table was obtained. This was used as an acid generator (4).

Example 5 Except that 322 g of 10% lithium bis(nonafluorobutanesulfonyl)imide aqueous solution was used instead of 370 g of 5% potassium nonafluorobutanesulfonate aqueous solution, 64.6 g of the cobalt salt (1e) as the salt of the cation and anion shown in the following table was obtained in the same manner as Example 4. This was used as an acid generator (5).

Example 6 Except that 30.1 g of [bis(3,5-difluorophenyl)][4-(2-hydroxyethoxy)-3,5-dimethylphenyl]copperium trifluoromethanesulfonate obtained in Preparation Example 3 was used instead of 37.6 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)copperium trifluoromethanesulfonate obtained in Preparation Example 1, and 40.6 g of 2,3,5-triiodobenzyl chloride was used instead of 20.8 g of 2-iodobenzyl chloride. In the same manner as in Example 1, 52.5 g of copperium salt (1f) as a salt of cations and anions shown in the following table was obtained. This was used as an acid generator (6).

Example 7 28.5 g of [bis(3,5-difluorophenyl)][4-(2-bromoethoxy)-3,5-dimethylphenyl]copperium trifluoromethanesulfonate obtained in Preparation Example 4 was dissolved in 115 g of methanol, and 18.6 g of potassium carbonate was added. Then, 63.5 g of 2,4,6-triiodophenol was added in small amounts at room temperature for 1 hour. Then, the reaction was continued for 12 hours to terminate the reaction. Next, 200 g of ion exchange water was added and stirred for 1 hour, and then 200 g of dichloromethane was added and stirred for another 1 hour, and the water layer was removed. 200 g of ion exchange water was added to the remaining organic layer for washing, and the washing operation of removing the water layer was performed 3 times. Thereafter, dichloromethane was distilled off under reduced pressure, and the obtained solid was washed with tert-butyl methyl ether and dried under reduced pressure. Thus, 32.2 g of the cation and anion salt (1 g) was obtained. This was used as an acid generator (7).

Example 8 37.6 g of [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)copperium trifluoromethanesulfonate obtained in Preparation Example 1 was dissolved in 263 g of acetonitrile, 24.6 g of potassium carbonate was added, 16.1 g of tert-butyl chloroacetate was added dropwise, and the temperature was raised to 50°C. The reaction was continued for 24 hours to terminate the reaction. Then, the obtained precipitate was filtered out and the solvent was removed under reduced pressure. Add 150 g of 2M hydrogen chloride 2-propanol solution to the precipitate after desolventization and dissolve it. After stirring for 12 hours, add 200 g of dichloromethane and 200 g of ion exchange water, stir for another hour, and remove the water layer. Add 200 g of ion exchange water to the remaining organic layer for washing, and perform the washing operation of removing the water layer three times. Then, cool to below 5°C, add 1.74 g of N,N-dimethylaminopyridine and 83.9 g of 2,4,6-triiodophenol, and stir for 12 hours. Next, 100 g of dilute hydrochloric acid was added and stirred for 1 hour. After removing the aqueous layer, the mixture was further washed once with 100 g of sodium hydroxide aqueous solution and three times with 100 g of ion exchange water, and the aqueous layer was removed. Thereafter, the solid obtained by distilling off dichloromethane under reduced pressure was washed with tert-butyl methyl ether and dried under reduced pressure. Thus, 37.0 g of the salt of the cation and anion described in the following table (1h) was obtained. It was used as an acid generator (8).

Comparative Example 1 Bis(3,5-difluorophenyl)sulfoxide was obtained by the same method as in Preparation Example 1 (Preparation of Compound (I-1)).

Dissolve 6.86 g of the obtained bis(3,5-difluorophenyl)sulfoxide in 30 g of benzene, and add 8.46 g of trifluoromethanesulfonic anhydride dropwise at a rate that the temperature in the system does not exceed -5°C. After the addition is completed, continue the reaction at room temperature for 1 hour to terminate the reaction. Remove the supernatant, add 50 g of ion exchange water to the oily precipitate at a rate that does not exceed 15°C, then add 75 g of tetrahydrofuran and 30 g of toluene, and stir for 1 hour. Remove the organic layer, add 30 g of toluene to the remaining water layer for washing, and perform the washing operation of removing the organic layer twice. Then, the aqueous layer was neutralized with sodium bicarbonate, and 100 g of dichloromethane was added for extraction. After removing the aqueous layer, 50 g of ion exchange water was added to the organic layer for washing, and the washing operation of removing the aqueous layer was performed three times. Then, the solvent was removed, and when crystals were precipitated, 150 g of methyl-tert-butyl ether was added to precipitate white crystals. The crystals were filtered out and dried under reduced pressure. Thus, 6.53 g of [bis(3,5-difluorophenyl)]phenylarsinium trifluoromethanesulfonate was obtained. It was used as an acid generator (9).

Comparative Example 2 [Bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate was obtained by the same method as in Preparation Example 1.

37.6 g of the obtained [bis(3,5-difluorophenyl)](4-hydroxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate and 43.2 g of triethylamine were added to 121 g of dichloromethane. Then, the mixture was cooled to below 5°C and 11.0 g of benzoyl chloride was added in small amounts over 2 hours. Then, the reaction was continued at room temperature for 1 hour to terminate the reaction. Then, 200 g of ion exchange water was added and stirred for 1 hour, and then 100 g of toluene was added and stirred for another 1 hour, and the precipitate was filtered out. The obtained precipitate was washed with tert-butyl methyl ether and dried under reduced pressure. Thus, 31.5 g of [bis(3,5-difluorophenyl)](4-benzoyloxy-3,5-dimethylphenyl)arsenic trifluoromethanesulfonate was obtained. This was used as an acid generator (10).

Comparative Example 3 Triphenylphosphine trifluoromethanesulfonate was used as the acid generator (11).

(Evaluation) The photosensitivity and solvent solubility of the acid generators obtained in the examples and comparative examples were evaluated by the following method. The results are shown in the following table.

<Photosensitivity evaluation 1> The acid generator was diluted with acetonitrile to a molar concentration of 2.5 mM, and Rhodamine B base (acid colorimetric reagent, manufactured by Sigma-Aldrich) was added to a molar concentration of 2.5 mM to prepare a sample solution.

The obtained sample solution was placed in a quartz cell with an optical path length of 1 cm, and electron beam exposure was performed using an EB exposure device (JEOL JBX-9300, manufactured by JEOL Ltd.) at an accelerating voltage of 100 kV and a cumulative light intensity of 50 μC/cm ^2. When the acid generator in the sample solution decomposes and generates acid by exposure, the generated acid reacts with the rhodamine B substrate and the absorbance at 556 nm increases. Therefore, by measuring the absorbance at 556 nm after exposure, the amount of acid generated can be calculated. The absorbance is measured using a spectrophotometer (UV-vis). Using a calibration curve (standard substance: p-toluenesulfonic acid), the acid concentration in the sample solution after exposure is quantified based on the absorbance at 556 nm of the sample solution after exposure. The acid generation rate is calculated by the following formula, and the photosensitivity is evaluated according to the following criteria based on the calculated acid generation rate. Acid generation rate (%) = acid concentration after exposure (mM) / acid generator concentration before exposure (mM) × 100

The photosensitivity was evaluated according to the following criteria. (Evaluation criteria) Excellent: Acid generation rate is 50% or more Good: Acid generation rate is 40% or more and less than 50% Acceptable: Acid generation rate is 20% or more and less than 40% Unacceptable: Acid generation rate is less than 20%

<Photosensitivity evaluation 2> For the acid generators obtained in Comparative Examples 1 and 3, the acid generation rate was calculated in the same manner as in Photosensitivity 1, except that the cumulative light amount of the EB exposure device was changed from 50 μC/cm ² to 100 μC/cm ^2. As a result, the acid generation rate of the acid generator obtained in Comparative Example 1 was more than 50%. The acid generation rate of the acid generator obtained in Comparative Example 3 was less than 40%. That is, the acid generator obtained in Comparative Example 1 can obtain a sufficient acid generation rate as long as the cumulative light amount of the electron beam is increased, but the acid generator obtained in Comparative Example 3 cannot obtain a sufficient acid generation rate even if the cumulative light amount of the electron beam is increased.

<Evaluation of solvent solubility> Add 0.1 g of acid generator to the test tube, add 0.2 g of PGMEA at a time at 25°C until the acid generator is completely dissolved, find the concentration of the acid generator when it is completely dissolved, and evaluate the solvent solubility according to the following criteria. (Evaluation criteria) Excellent: Acid generator concentration is 5% by weight or more Good: Acid generator concentration is 2% by weight or more and less than 5% by weight Acceptable: Acid generator concentration is 0.1% by weight or more and less than 2% by weight Unacceptable: Acid generator concentration is less than 0.1% by weight

[Table 1] Table 1 Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Acid generator Cation A-1 A-1 A-2 A-2 A-2 Anions (X ^- ) CF ₃ SO ₃ ^- Br ^- CF ₃ SO ₃ ^- C ₄ F ₉ SO ₃ ^- (C ₄ F ₉ SO ₂ ) ₂ N ^- Reviews Light sensitivity good good Excellent Excellent Excellent Solvent solubility good qualified good Excellent Excellent

[Table 2] Table 2 Embodiment 6 Embodiment 7 Embodiment 8 Acid generator Cation A-3 A-4 A-5 Anions (X ^- ) CF ₃ SO ₃ ^- CF ₃ SO ₃ ^- CF ₃ SO ₃ ^- Reviews Light sensitivity Excellent Excellent Excellent Solvent solubility good good good

[Table 3] Table 3 Comparison Example 1 Comparison Example 2 Comparison Example 3 Acid generator Cation B-1 B-2 B-3 Anions (X ^- ) CF ₃ SO ₃ ^- CF ₃ SO ₃ ^- CF ₃ SO ₃ ^- Reviews Light sensitivity qualified Failure Failure Solvent solubility good good qualified

※The cations in the table are represented by the following formulas (A-1) to (A-5) and (B-1) to (B-3).

The acid generator of Comparative Example 1 is sensitive to electron beams, but a small exposure dose cannot generate sufficient acid. In order to obtain the same acid generation rate as the acid generator of the present invention, the exposure dose needs to be doubled. The acid generators of Comparative Examples 2 and 3 are less sensitive to electron beams, and the acid generator of Comparative Example 3 cannot generate sufficient acid even if the exposure dose is doubled. In contrast, it can be seen that the acid generator of the present invention (or cobalt salt (1)) has a "structure in which cobalt is substituted with an aryl group having an iodinated aryl group and an aryl group having a fluorine atom-containing group", so the sensitivity to electron beams is significantly improved, and acid is efficiently generated with a small exposure dose. Furthermore, it can be seen that the acid generator of the present invention has solvent solubility, and has particularly excellent solvent solubility when it contains specific relative anions.

It can be seen that the acid generator of the present invention can be suitably used as an acid generator for photoresists (especially acid generators for photoresists used in photolithography using light with a wavelength of less than 20 nm) because of the above-mentioned properties. If a photoresist containing the acid generator of the present invention (or coronium salt (1)) is used to perform photolithography (especially photolithography using light with a wavelength of less than 20 nm), fine patterns can be formed with good precision, thereby achieving large-capacity and miniaturization of electronic devices.

As a summary of the above, the structure and variations of the present invention are described below. [1] A cobalt salt represented by formula (1). [2] The cobalt salt described in [1], wherein the monovalent relative anion is a sulfonate anion, a sulfonylimide anion, or a halogen ion. [3] An acid generator comprising the cobalt salt described in [1] or [2]. [4] The acid generator described in [3], which is an acid generator for extreme ultraviolet rays or an acid generator for electron beams. [5] A photoresist comprising the cobalt salt described in [1] or [2] and an acid-reactive compound. [6] A method for manufacturing an electronic device, comprising the step of using the photoresist described in [5] and performing pattern formation by photolithography. [7] A use of the cobalt salt described in [1] or [2] as an acid generator. [8] A use of the cobalt salt described in [1] or [2] as an acid generator for extreme ultraviolet light. [9] A use of the cobalt salt described in [1] or [2] as an acid generator for electron beams. [10] A use of the cobalt salt described in [1] or [2] as an acid generator for photolithography using light with a wavelength of less than 20 nm. [11] A use of a composition comprising a cobalt salt and an acid-reactive compound as described in [1] or [2], which is used as a photoresist. [12] A use of a composition comprising a cobalt salt and an acid-reactive compound as described in [1] or [2], which is used as a photoresist for photolithography using light with a wavelength of less than 20 nm. [Industrial Applicability]

The cobalt salt (1) of the present invention has excellent sensitivity to light with a wavelength of less than 20 nm, and can be easily decomposed to generate acid (H ⁺ X ^- ) by irradiating light of the above wavelength. In addition, the above cobalt salt (1) has excellent solvent solubility. If the cobalt salt (1) having the above characteristics is added to a photoresist, it can be evenly dispersed, and good fine pattern forming properties can be given to the photoresist. Therefore, the above cobalt salt (1) is suitable as an acid generator used in photolithography using light with a wavelength of less than 20 nm.

without

without

Claims (6)

A cobalt salt represented by the following formula (1): (wherein, ^Rf1 and ^Rf2 are the same or different and represent a fluorine atom or a fluoroalkyl group; L is a group selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a carbonate bond, and a divalent group formed by linking at least one of the above groups with a alkyl group; n1, n2, and n3 are the same or different and represent an integer of 1 to 5; ^X- represents a monovalent relative anion). The cobalt salt of claim 1, wherein the monovalent relative anion is a sulfonate anion, a sulfonyl imide anion, or a halogen ion. An acid generator comprising the cobalt salt of claim 1 or 2. The acid generator of claim 3 is an acid generator for extreme ultraviolet rays or an acid generator for electron beams. A photoresist comprising the cobalt salt of claim 1 or 2 and an acid-reactive compound. A method for manufacturing an electronic device, comprising the step of using the photoresist of claim 5 and performing pattern formation by photolithography.