JP2006124716A - Method for producing copolymer for semiconductor lithography - Google Patents

Abstract

The present invention provides a method for producing a copolymer for semiconductor lithography which is suitably used for a coating film forming composition such as a resist film forming composition used for forming a fine pattern in semiconductor manufacturing.
The present invention includes at least a repeating unit (A) having a structure that is decomposed by an acid and becomes soluble in an alkali developer, and a repeating unit (B) having a polar group for enhancing adhesion to a semiconductor substrate. And a method for producing a copolymer for semiconductor lithography, wherein a solution containing two or more types of monomers having an ethylenic double bond that gives the repeating unit is subjected to radical polymerization by dropping into a heated solvent. When producing a copolymer for semiconductor lithography, a semiconductor that is allowed to undergo radical polymerization by dropping a solution into a heated solvent in the presence of a polymerization inhibitor or oxygen as a polymerization inhibiting component in a solution containing the monomer before dropping. The present invention relates to a method for producing a copolymer for lithography.
[Selected drawing] None

Description

  The present invention relates to a method for producing a copolymer suitable as a film-forming polymer such as a resist polymer, an antireflection film polymer, and a multilayer film underlayer film polymer used in semiconductor lithography, and in particular, a high molecular weight of 100,000 or more. The present invention relates to a method for producing a copolymer for semiconductor lithography, which does not contain a molecular weight component (high polymer) and can obtain a copolymer with very few occurrences of defects (defects) in a resist pattern.

In lithography in the manufacture of semiconductors, formation of finer patterns is required as the degree of integration increases. Shortening the wavelength of the exposure light source is indispensable for pattern miniaturization, but now lithography using krypton fluoride (KrF) excimer laser (wavelength 248 nm) is becoming the mainstream, and argon fluoride (ArF) excimer laser light Lithography with a line width of 100 nm or less with a wavelength of 193 nm is also being put into practical use. Furthermore, various radiation lithography techniques with short wavelengths using fluorine dimer (F ₂ ) excimer laser light (wavelength 157 nm), extreme ultraviolet light (EUV), X-rays, electron beams, etc. are in the development stage.

  In these semiconductor lithography, a resist film that forms a pattern to be transferred to a substrate by utilizing the fact that the solubility of the resist polymer in an alkaline developer is changed by acting an acid on the resist polymer, and the resist Various coating films are applied to the upper layer or lower layer of the film. For example, as a lower layer film, an antireflection film for accurately forming a fine resist pattern by suppressing reflected light from the substrate, or flattening the substrate surface when further forming a resist pattern on the substrate on which the pattern is formed For example, a flattening film used as a lower layer of a resist film for the purpose of forming a resist film, a lower layer film in a multilayer resist for transferring a resist pattern by dry etching, and the like.

  For the coating film such as the resist film, a coating solution is prepared by dissolving a copolymer for lithography having the function of each coating film and other additives in an organic solvent, and this is applied to the substrate by a method such as spin coating. After the application, it is formed by removing the solvent by heating, if necessary. In addition to the physical properties such as optical properties, chemical properties, coatability and adhesion to the substrate or lower layer film required for resist films and antireflection films, these lithographic copolymers have fine pattern formation. There is a demand for basic properties as a copolymer for coating films, such as the absence of obstructing foreign substances.

  The resist polymer used for the resist film includes a negative type in which the solubility in an alkali developer is lowered by the action of an acid and a positive type in which the solubility in an alkali developer is increased by the action of an acid. A positive resist polymer is a repeating unit having a structure in which a non-polar substituent is decomposed by an acid and a polar group soluble in an alkali developer is expressed, and a polar group for improving adhesion to a semiconductor substrate. The unit is an essential component, and includes a repeating unit having a polar or nonpolar substituent for adjusting the solubility in a resist solvent or an alkali developer as necessary. As the repeating unit having a polar group for imparting substrate adhesion, for example, hydroxystyrenes are mainly used when a KrF excimer laser is used as an exposure source, and hydroxystyrene is used when an ArF excimer laser is used. In order to absorb light having a wavelength of 193 nm, (meth) acrylates having a polar group have been studied.

As such a positive resist polymer, in the KrF series, for example, a copolymer (for example, see Patent Documents 1 to 4) in which a (meth) acrylic acid monomer and a styrene monomer are combined or a part of hydroxystyrene is used. Polymers protected with acetal (for example, see Patent Documents 5 to 8, etc.) are known. In ArF series, for example, a copolymer of (meth) acrylic acid monomer having a lactone structure (for example, Patent Document 9). -10 etc.) are known.

  Examples of the polymer used for the antireflection film include aromatic compounds containing vinyl compounds such as styrene, styrene derivatives, anthracenylmethyl (meth) acrylate, vinyl compounds containing acrylamide derivatives, hydroxyl groups, and epoxy groups. Polymers obtained by copolymerizing alkyl (meth) acrylate or the like (for example, see Patent Documents 11 to 14) are known. As the polymer used for the planarizing film, a copolymer of hydroxystyrene and a monomer such as styrene, alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, etc. (see, for example, Patent Document 15) is known. It has been.

  On the other hand, as resist patterns become finer, it is necessary to manage even finer resist pattern defects, and stricter performance is also required for the above-mentioned polymer for film formation for semiconductor lithography. Yes. The cause of the resist pattern defect is the presence of foreign matter in the resist composition. Conventionally, such foreign matter in the resist solution is filtered through a filter having a micropore size or a zeta potential. (See, for example, Patent Documents 16 to 17, and the like) Foreign substances such as dust existing in the environment can be completely removed by this method. However, an extremely minute hardly soluble substance cannot be completely removed by filtration, which has been a major obstacle in miniaturization of pattern formation in semiconductor lithography.

  According to the study by the present inventors, as one of such extremely minute hardly soluble substances, a very small amount of a high molecular weight component (hereinafter sometimes referred to as “high polymer”) having a molecular weight of 100,000 or more. It has been found that it has a significant influence on the formation of resist patterns. That is, the solubility of the polymer generally depends on the molecular weight, and the high polymer molecule is difficult to dissolve in the resist solvent or alkaline water, and a fine pattern is formed by lithography even though it is apparently dissolved in the solvent or alkaline water. It is thought that it sometimes causes defects. Furthermore, when a high polymer is present, it is considered that insoluble foreign matter (particles in liquid) grows and precipitates with the high polymer as a nucleus over time while the resist solution is stored. Such an insoluble foreign matter is very likely to cause a defect in a resist pattern, and it is strongly desired to provide a method for producing a copolymer for semiconductor lithography with a small increase in liquid particles during storage. It was.

Polymers for film formation for semiconductor lithography, including resist polymers, can generally be produced by radical solution polymerization of raw material monomers, but if a small amount of radicals are generated before reaching the polymerization temperature, the polymer concentration will be Since the radical concentration is low, a high polymer is generated according to the relationship represented by the following formula (1), which is considered to have the above-mentioned significant influence on the formation of the resist pattern.
P _n ∝ [M] / [R ·] (1)
(Here, P _n represents the molecular weight of the polymer produced, [M] represents the monomer concentration, and [R ·] represents the radical concentration.)

For example, in the case of a so-called batch polymerization method in which a monomer and a polymerization initiator are dissolved in a solvent and polymerized by heating to the polymerization temperature, the retention time before the temperature rise and the time to reach the polymerization temperature are compared with the monomer concentration. A high amount of radicals are generated, and high polymers are easily formed. Also, a method in which a monomer is dissolved in a polymerization solvent and heated to a polymerization temperature and then a polymerization initiator is added (see, for example, Patent Document 18) is also known. However, this method has a drawback in that a high polymer is easily generated by radicals generated in a minute amount due to impurities in the monomer solution while the solution containing only the monomer is heated. Furthermore, a so-called dropping polymerization method (for example, see Patent Documents 19 to 24) in which a solution in which a monomer and a polymerization initiator are dissolved in a solvent is dropped into a solvent heated to a polymerization temperature to perform polymerization is also known, Also in this method, there is a problem that a high polymer is generated by radicals generated in a minute amount during a holding time from when the monomer and the polymerization initiator are mixed to when the monomer is dropped.

In addition, in the radical polymerization reaction, it is often performed to remove radical scavenging substances such as oxygen and polymerization inhibitor in advance before polymerization by degassing the solvent or purifying the monomer (for example, However, according to the study by the present inventors, it has been found that such an operation causes the formation of a high polymer.
JP 59-45439 A JP-A-5-113667 JP-A-7-209868 JP 11-65120 A JP 62-115440 A JP-A-4-219757 JP-A-3-223860 JP-A-4-104251 JP-A-9-73173 Japanese Patent Laid-Open No. 10-239846 JP 2000-313779 A JP 2001-27810 A JP 2001-192411 A JP 2001-226324 A JP 2003-57828 A JP-A-5-307263 JP 2001-350266 A JP 2001-109153 A JP-A-4-269754 (Example) Japanese Patent Laid-Open No. 5-39444 (Example) JP-A-5-247386 (Example) Japanese Patent Laid-Open No. 5-311110 (Example) Japanese Patent Laid-Open No. 11-231538 International Publication No. 99/50322 JP 2003-221403 A

  The present invention has been made in view of the background art as described above, and its purpose is to provide a resist film forming composition used for fine pattern formation in semiconductor manufacturing, a multilayer resist underlayer film forming composition, and an antireflection coating. Semiconductor lithography that is suitably used for film-forming compositions such as film-forming compositions, and that does not contain high polymers, has excellent storage stability, and has very few resist pattern defects when used in semiconductor lithography. Another object of the present invention is to provide a method for producing a copolymer.

As a result of diligent studies to solve the above-mentioned problems, the present inventors have found that, when producing a copolymer for semiconductor lithography by radical polymerization, a polymerization inhibitor component is added to a solution containing monomers according to the technical common sense of those skilled in the art. On the contrary, the inventors have found that the formation of a high polymer can be suppressed by coexistence, and the present invention has been completed.

（式中、Ｒ_１は水素原子又はメチル基を表わし、−ＯＲはオルソ位には結合しない。）
一般式（２）

（式中、Ｒ_２は水素原子、メチル基又はトリフルオロメチル基を表わす。）
一般式（３）

（式中、Ｒｅ_１及びＲｅ_２はいずれか一方が水素原子で、他方は−Ｃ（＝Ｏ）ＯＲ基を表わす。）
一般式（４）

（式中、Ｒ_４は水素原子又はトリフルオロメチル基を表わす。）
一般式（５）

（式中、Ｒ_５はメチル基を表わす。）
一般式（６）

（式中、Ｒ_６は水素原子を表わす。）
一般式（７）

（式中、Ｒ_７は水素原子又はトリフルオロメチル基を表わす。）
一般式（８）

｛式（１）〜（８）において、Ｒが酸解離性基の場合は繰り返し単位（Ａ）を、極性基の場合は繰り返し単位（Ｂ）を表し、酸解離性保護基としてのＲは、ｔｅｒｔ−ブチル基、ｔｅｒｔ−アミル基、１−メチル−１−シクロペンチル基、１−エチル−１−シクロペンチル基、１−メチル-１−シクロヘキシル基、１−エチル−１−シクロヘキシル基、２−メチル−２−アダマンチル基、２−エチル−２−アダマンチル基、２−プロピル−２−アダマンチル基、２−（１−アダマンチル）−２−プロピル基、８−メチル−８−トリシクロ［５.２.１.０^2,6］デカニル基、８−エチル−８−トリシクロ［５.２.１.０^2,6］デカニル基、８−メチル−８−テトラシクロ［４.４.０.１^2,5.１^7,10］ドデカニル基、８−エチル−８−テトラシクロ［４.４.０.１^2,5.１^7,10］ドデカニル基等の飽和炭化水素基；１−メトキシエチル基、２−エトキシエチル基、１−ｉｓｏ−プロポキシエチル基、１−ｎ−ブトキシエチル基、１−ｔｅｒｔ−ブトキシエチル基、１−シクロペンチルオキシエチル基、１−シクロヘキシルオキシエチル基、１−トリシクロ［５.２.１.０^2,6］デカニルオキシエチル基、１−メトキシメチル基、２−エトキシメチル基、１−ｉｓｏ−プロポキシメチル基、１−ｎ−ブトキシメチル基、１−ｔｅｒｔ−ブトキシメチル基、１−シクロペンチルオキシメチル基、１−シクロヘキシルオキシメチル基、１−トリシクロ［５.２.１.０^2,6］デカニルオキシメチル基、ｔｅｒｔ−ブトキシカルボニル基を表し、極性基としてのＲは、γ−ブチロラクトン、γ−バレロラクトン、δ−バレロラクトン、１,３−シクロヘキサンカルボラクトン、２,６−ノルボルナンカルボラクトン、４−オキサトリシクロ［５.２.１.０^2,6］デカン−３−オン、メバロン酸δ−ラクトン、ヒドロキシメチル基、ヒドロキシエチル基、ヒドロキシプロピル基、３−ヒドロキシ−１−アダマンチル基を表す。｝ That is, the present invention improves the adhesion to the semiconductor substrate with the repeating unit (A) represented by at least the general formulas (1) to (8) and having a structure that is decomposed by an acid and becomes soluble in an alkaline developer. A method for producing a copolymer for semiconductor lithography having a repeating unit (B) having a polar group, wherein a solution containing two or more monomers having an ethylenic double bond giving the repeating unit is heated. When a copolymer for semiconductor lithography is produced by radical polymerization by dropping into the solution, a polymerization-inhibiting component in the solution containing the monomer before dropping is polymerized at a concentration of 20 mol ppm to 5000 mol ppm with respect to the monomer. Inhibitors (excluding nitrogen-containing stable free radical agents) or 400 mol ppm to 10,000 mol ppm Coexist element, there is provided a method of manufacturing a copolymer for semiconductor lithography, characterized in that to radical polymerization was dropped into a solvent and the solution was heated.
General formula (1)

(In the formula, R ₁ represents a hydrogen atom or a methyl group, and —OR is not bonded to the ortho position.)
General formula (2)

(In the formula, R ₂ represents a hydrogen atom, a methyl group or a trifluoromethyl group.)
General formula (3)

(In the formula, _one of Re ₁ and Re ₂ represents a hydrogen atom, and the other represents a —C (═O) OR group.)
General formula (4)

(In the formula, R ₄ represents a hydrogen atom or a trifluoromethyl group.)
General formula (5)

(In the formula, R ₅ represents a methyl group.)
General formula (6)

(In the formula, R ₆ represents a hydrogen atom.)
General formula (7)

(In the formula, R ₇ represents a hydrogen atom or a trifluoromethyl group.)
General formula (8)

{In the formulas (1) to (8), when R is an acid dissociable group, it represents a repeating unit (A), and when it is a polar group, it represents a repeating unit (B), and R as an acid dissociable protecting group is tert-butyl group, tert-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 2-methyl- 2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 8-methyl-8-tricyclo [5.2.1. 0 ^2,6] decanyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6] decanyl group, 8-methyl-8-tetracyclo [4.4.0.1 ^{2, 5} .1 ^7,10 ] dodecanyl group, 8-ethyl-8-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl saturated hydrocarbon group such as a group; a 1-methoxyethyl group, 2-ethoxyethyl group, 1-an iso-propoxyethyl group, 1-n-butoxyethyl group, 1 -Tert-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxyethyl group, 1-methoxymethyl group, 2- Ethoxymethyl group, 1-iso-propoxymethyl group, 1-n-butoxymethyl group, 1-tert-butoxymethyl group, 1-cyclopentyloxymethyl group, 1-cyclohexyloxymethyl group, 1-tricyclo [5.2. 1.0 ^2,6] decanyl oxymethyl group, a tert- butoxycarbonyl radical, R as the polar group, .gamma.-butyrolactone, .gamma.-valerolactone, .delta. Bas Rorakuton, 1,3 cyclohexane lactone, 2,6-norbornanecarbolactone, 4-oxa-tricyclo [5.2.1.0 ^{2, 6]} decan-3-one, mevalonate δ- lactone, hydroxymethyl group , A hydroxyethyl group, a hydroxypropyl group, and a 3-hydroxy-1-adamantyl group. }

  According to the present invention, a coexistence of a polymerization inhibitor component can trap radicals generated in a trace amount particularly at a temperature lower than the polymerization temperature. Therefore, a copolymer for semiconductor lithography that does not contain a high polymer can be produced. it can. In addition, since the copolymer obtained by the method of the present invention does not generate high polymer and insoluble foreign matters resulting from it, there is little generation of liquid particles over time during storage, and resists when used in semiconductor lithography. It is expected that the occurrence of pattern defects is small.

  In the present invention, as a raw material monomer used for radical copolymerization in the production of a copolymer for semiconductor lithography, ethylene used for the production of resist polymers, multilayer resist underlayer films, antireflection film polymers and the like is generally used. As long as the monomer has a polymerizable double bond, it can be used without any particular restrictions. However, in terms of resolution and transparency of the resulting copolymer for semiconductor lithography, an acrylate monomer and / or methacrylic acid It is preferable to include at least one ester monomer.

  First, when the copolymer obtained by the present invention is used as a positive resist polymer, the copolymer is at least a repeating unit having a structure that is decomposed by an acid and becomes soluble in an alkali developer, more specifically. Specifically, a repeating unit (A) having a structure in which a nonpolar substituent is decomposed by an acid and a polar group soluble in an alkali developer is expressed, and a repeating group having a polar group for improving adhesion to a semiconductor substrate The unit (B) is an essential component, and includes a repeating unit (C) having a nonpolar substituent for adjusting the solubility in a resist solvent or an alkali developer as necessary.

  The repeating unit (A) which is decomposed by an acid and becomes soluble in an alkali developer means a structure generally used as a resist from the past, and a monomer having a structure which is decomposed by an acid and becomes alkali-soluble. Protecting group which is polymerized or a monomer having an alkali-soluble structure is polymerized and then a substituent having an alkali-soluble group in the alkali-soluble structure (alkali-soluble substituent) is dissociated by an acid without dissolving in alkali It can be obtained by protecting with (acid-dissociable protecting group).

  Examples of the monomer having a structure that is decomposed by an acid and becomes alkali-soluble include compounds in which an acid-dissociable protecting group is bonded to a monomer containing an alkali-soluble substituent, for example, nonpolar acid-dissociable protection And compounds having a phenolic hydroxyl group, a carboxyl group or a hydroxyfluoroalkyl group protected with a group.

Examples of such monomers include hydroxystyrenes such as p-hydroxystyrene, m-hydroxystyrene, and p-hydroxy-α-methylstyrene; acrylic acid, methacrylic acid, maleic acid, fumaric acid, α-trifluoromethylacrylic. acid, 5-norbornene-2-carboxylic acid, 2-trifluoromethyl-5-norbornene-2-carboxylic acid, carboxymethyl tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecyl methacrylate Carboxylic acids having an ethylenic double bond; p- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) styrene, 2- (4- (2-hydroxy-1, 1,1,3,3,3-hexafluoro-2-propyl) cyclohexyl) -1,1,1,3,3,3-hexafluoropropyl acrylate 2- (4- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) cyclohexyl) -1,1,1,3,3,3-hexafluoropropyl Examples include monomers having a hydroxyfluoroalkyl group such as trifluoromethyl acrylate and 5- (2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl) methyl-2-norbornene. it can.

Examples of the acid dissociable protecting group include tert-butyl group, tert-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, and 1-ethyl. -1-cyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 8-methyl- 8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, 8-methyl-8-tetracyclo [4. 4.0.1 ^2,5 .1 ^7,10] dodecanyl group, 8-ethyl-8-tetracyclo [
4.4.0.1 ^2,5 .1 ^7,10] dodecanyl saturated hydrocarbon group such as a group; a 1-methoxyethyl group, 2
-Ethoxyethyl group, 1-iso-propoxyethyl group, 1-n-butoxyethyl group, 1-tert-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo [5.2 .1.0 ^2,6 ] decanyloxyethyl group, 1-methoxymethyl group, 2-ethoxymethyl group, 1-iso-propoxymethyl group, 1-n-butoxymethyl group, 1-tert-butoxymethyl group, Examples include oxygen-containing hydrocarbon groups such as 1-cyclopentyloxymethyl group, 1-cyclohexyloxymethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxymethyl group, and tert-butoxycarbonyl group. be able to.

Among these acid dissociable protecting groups, those containing an alicyclic structure increase the etching resistance of the resulting resist polymer, and there is a difference in solubility in an alkali developer depending on the presence or absence of the acid dissociable protecting group. Since it becomes large, it is preferable. Specific examples of the alicyclic structure include a cyclopentane ring, a cyclohexane ring, an isobornane ring, a norbornane ring, an adamantane ring, a tricyclo [5.2.1.0 ^2,6 ] decane ring, a tetracyclo [ 4.4.0.1 ^2,5 .1 ^7,10] etc. dodecane ring, can be exemplified an alicyclic structure having 5 to 20 carbon atoms.

  After polymerizing a monomer having an alkali-soluble structure, when the alkali-soluble substituent in the alkali-soluble structure is protected with an acid-dissociable protecting group, the compound having the alkali-soluble group is used as it is for the polymerization reaction. Thereafter, an acid-dissociable protecting group can be introduced by reacting with a compound that gives a substituent that does not dissolve in an alkali such as vinyl ether or halogenated alkyl ether under an acid catalyst. Examples of the acid catalyst used in the reaction include p-toluenesulfonic acid, trifluoroacetic acid, and strongly acidic ion exchange resin.

On the other hand, examples of the monomer that gives the repeating unit (B) having a polar group for improving the adhesion to the semiconductor substrate include compounds having a phenolic hydroxyl group, a carboxyl group, or a hydroxyfluoroalkyl group as the polar group. Specifically, for example, as a monomer containing an alkali-soluble group, the above-described hydroxystyrenes, carboxylic acids having an ethylenic double bond, monomers having a hydroxyfluoroalkyl group, and further polar groups are substituted. In addition to monomers, examples include monomers in which a polar group is bonded to an alicyclic structure such as a norbornene ring or a tetracyclododecene ring.

As the polar group introduced into the repeating unit (B) as a substituent, those having a lactone structure are particularly preferable. For example, γ-butyrolactone, γ-valerolactone, δ-valerolactone, and 1,3-cyclohexanecarbolactone. Examples include substituents containing a lactone structure such as 2,6-norbornanecarbolactone, 4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one, and mevalonic acid δ-lactone. . Examples of polar groups other than the lactone structure include hydroxyalkyl groups such as a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a 3-hydroxy-1-adamantyl group.

Furthermore, as a monomer which contains a repeating unit (C) having a nonpolar substituent for adjusting the solubility in a resist solvent or an alkali developer, which is contained as necessary, styrene, α-methylstyrene, p -Aromatic compounds having an ethylenic double bond such as methylstyrene and indene; acrylic acid, methacrylic acid, trifluoromethylacrylic acid, norbornenecarboxylic acid, 2-trifluoromethylnorbornenecarboxylic acid, carboxytetracyclo [4.4 0.1 ^{2,5.1 7,10} ] ester compounds in which an acid-stable nonpolar group is substituted on a carboxylic acid having an ethylenic double bond such as dodecyl methacrylate; ethylenic diene such as norbornene and tetracyclododecene Examples include alicyclic hydrocarbon compounds having a heavy bond. Examples of acid-stable nonpolar substituents for ester substitution with the carboxylic acid include methyl, ethyl, cyclopentyl, cyclohexyl, isobornyl, and tricyclo [5.2.1.0 ^2,6 ] decanyl. group, 2-adamantyl group, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10]
A dodecyl group etc. can be mentioned.

  These monomers can be used by mixing one type or two or more types for each of the repeating units (A), (B) and (C), and the composition ratio of each repeating unit in the resulting resist polymer is: It can be selected within a range that does not impair the basic performance as a resist. That is, in general, the repeating unit (A) is preferably 10 to 70 mol%, and more preferably 10 to 60 mol%. The composition ratio of the repeating unit (B) is preferably 30 to 90 mol%, more preferably 40 to 90 mol%, but for monomer units having the same polar group, 70 mol% or less. It is preferable that Furthermore, the composition ratio of the repeating unit (C) is preferably 0 to 50 mol%, more preferably 0 to 40 mol%.

  In addition, when the copolymer obtained by the present invention is used as a polymer for a lower layer coating film or an antireflection film of a multilayer resist, it has a structure in which the resist polymer structure is decomposed with an acid and becomes alkali-soluble. A polymer having a structure excluding the unit (A) is used. Since the composition ratio of each repeating unit in the copolymer varies depending on the intended use of the coating film, it cannot be defined unconditionally, but in general, the composition ratio of the repeating unit (B) is selected from the range of 10 to 100 mol%, The composition ratio of the repeating unit (C) is selected from the range of 0 to 90 mol%.

  Furthermore, when using the copolymer obtained by the present invention as an antireflection film, it is necessary to include a crosslinking point and a structure that absorbs radiation irradiated in photolithography, and the crosslinking point includes a hydroxyl group, The reactive substituent which can be bridge | crosslinked by ester bond, urethane bond, etc., such as an amino group, a carboxyl group, an epoxy group, is mentioned. As monomers containing reactive substituents that serve as crosslinking points, in addition to hydroxystyrenes such as p-hydroxystyrene and m-hydroxystyrene, the hydroxyl group, amino group, carboxyl group, and epoxy group described above are also included in the monomers exemplified above. A monomer substituted with a reactive substituent such as can be used as appropriate.

  The structure that absorbs radiation varies depending on the wavelength of the radiation to be used. For example, for ArF excimer laser light, a structure including a benzene ring and its analog is preferably used. Examples of the monomer having such a structure include styrenes such as styrene, α-methylstyrene, p-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, and derivatives thereof; substituted or unsubstituted phenyl (meth) acrylate, Examples thereof include aromatic-containing esters having an ethylenic double bond such as substituted or unsubstituted naphthalene (meth) acrylate and substituted or unsubstituted anthracenemethyl (meth) acrylate. The monomer having a structure that absorbs radiation may be introduced as either the repeating unit (B) or (C) depending on the presence or absence of a polar group, but the composition ratio as a monomer having a structure that absorbs radiation is 10 It is preferably selected from the range of ˜100 mol%.

  In the present invention, the copolymer for semiconductor lithography can be obtained by radical polymerization of two or more types of monomers selected from the above monomer group in the presence of a polymerization initiator in a polymerization solvent.

The polymerization initiator used in the polymerization reaction is not particularly limited as long as it is generally used as a radical generator. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2- Decanoyl such as methylbutyronitrile) dimethyl 2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile), 4,4′-azobis (4-cyanovaleric acid); Organic peroxides such as peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, succinic acid peroxide, tert-butylperoxy-2-ethylhexanoate alone Or it can mix and use.

  A chain transfer agent is not particularly required, but known examples include dodecyl mercaptan, mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, and 4,4-bis (trifluoromethyl) -4-hydroxy-1-mercaptobutane. These thiol compounds can be used alone or in combination.

  The amount of polymerization initiator and chain transfer agent used varies depending on the raw material monomers used in the polymerization reaction, the polymerization initiator, the type of chain transfer agent, the polymerization temperature, the polymerization solvent, the polymerization method, the purification conditions, etc. Although not specified, the optimum amount is used to achieve the desired molecular weight. In general, if the weight average molecular weight of the copolymer is too high, the solubility in the solvent or alkali developer used during coating formation will be low, while if too low, the coating performance will be poor. The average molecular weight is preferably adjusted to be in the range of 2,000 to 40,000, and more preferably adjusted to be in the range of 3,000 to 30,000.

  As a polymerization method for producing the copolymer, solution polymerization is preferable, and radical copolymerization is preferably performed in a state where the raw material monomer, the polymerization initiator and, if necessary, the chain transfer agent are dissolved in the polymerization solvent. Solution polymerization can be performed by, for example, a so-called batch polymerization method in which all monomers, a polymerization initiator, and if necessary, a chain transfer agent are dissolved in a polymerization solvent and heated to a polymerization temperature, or a monomer is dissolved in a solvent and heated to the polymerization temperature. After that, an initiator addition method in which a polymerization initiator is added, a monomer, a polymerization initiator, a part or all of a chain transfer agent as needed is mixed or independently dropped into a polymerization system heated to a polymerization temperature It can be carried out by a dropping polymerization method or the like. Of these, the drop polymerization method is preferable because the difference between lots can be reduced.

In the polymerization system heated to the polymerization temperature or the solution containing the monomer before heating to the polymerization temperature, such as the solution charged into the polymerization tank in the batch polymerization method, the monomer solution supplied to the polymerization tank in the dropping polymerization method, or the like. It is essential to allow a polymerization inhibitor component to coexist in the solution containing the monomer before dropping. The solution containing the monomer may be composed of only the monomer if it is a liquid monomer, but generally contains a monomer and a solvent, and further contains a polymerization initiator, a chain transfer agent, and the like as necessary.

  In the present invention, the polymerization inhibitor component coexisting in the monomer-containing solution can include a compound or oxygen generally used as a polymerization inhibitor, and any known polymerization inhibitor can be used as the polymerization inhibitor. Can be used. Specific examples of the polymerization inhibitor include hydroquinone and hydroquinone derivatives such as 4-methoxyphenol, tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone; benzoquinones such as benzoquinone, methylbenzoquinone and tert-butylbenzoquinone. Derivatives; catechol derivatives such as catechol and 4-tert-butylcatechol; phenothiazine and derivatives thereof; N-nitrosophenylhydroxylamine and derivatives thereof; 2,2,6,6-tetramethylpiperidine-1-oxyl free radical and derivatives thereof These can be used alone or in combination.

  The amount of the polymerization inhibitor that is allowed to coexist in the solution containing the monomer is preferably 20 mol ppm or more with respect to the monomer because the effect of capturing radicals is low if the amount is too small. Is preferably 0.1 mol% or more based on the amount of the polymerization initiator. Further, the upper limit of the amount of the polymerization inhibitor is not particularly limited, but if it is too large, the polymerization reaction does not proceed sufficiently, and it remains in the copolymer even after purification, and depending on the compound, radiation used for lithography may be present. Since it may absorb, it is preferable to set it as 5,000 molppm or less with respect to a monomer, and it is more preferable to set it as 3,000 molppm. In the case of a solution in which a monomer and a polymerization initiator coexist, it is preferably 20 mol% or less, more preferably 10 mol% or less, relative to the polymerization initiator.

  Since oxygen also has a radical scavenging ability, it can be used as a polymerization inhibiting component of the present invention. However, since the radical scavenging effect is lower than that of the above-described polymerization inhibitor, the present invention is based only on oxygen without using the above-described polymerization inhibitor. In order to achieve the above objective, a relatively large amount of oxygen needs to coexist. In this case, the amount of oxygen dissolved in the monomer solution is preferably 400 mol ppm or more with respect to the monomer, and preferably 2 mol% or more with respect to the polymerization initiator when a polymerization initiator coexists.

  Examples of the method for allowing the oxygen having the above concentration to coexist with the monomer include a method in which a solution containing the monomer is maintained in an oxygen or air atmosphere, or oxygen or air is bubbled into the solution. Moreover, you may use the solvent hold | maintained in oxygen or air atmosphere, or the solvent which bubbled oxygen or air for preparation of the solution containing a monomer.

  In addition, it is necessary to polymerize in an oxygen atmosphere because there are safety problems, and it becomes difficult to obtain a copolymer with stable quality because the dissolved oxygen concentration in the polymerization system changes due to heating. It is not preferable that a large amount of oxygen coexists. Therefore, the upper limit of the dissolved oxygen amount is preferably 10,000 mol ppm (1 mol%) or less with respect to the monomer, and when the polymerization initiator coexists, it is 50 mol% or less with respect to the polymerization initiator. Is preferred. Also, the gas zone in the polymerization system is replaced with an inert gas such as nitrogen before introducing the monomer-containing solution or heating to the polymerization temperature so that the oxygen concentration in the gas zone does not exceed the explosion limit. To do.

The solvent containing the monomer and / or the solvent used for the polymerization reaction is not particularly limited as long as it is a solvent that can stably dissolve the raw material monomer, the obtained copolymer, the polymerization initiator, and the chain transfer agent. Specific examples of suitable solvents include ketones such as acetone, methyl ethyl ketone, methyl amyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, glyme, and propylene glycol monomethyl ether; esters such as ethyl acetate and ethyl lactate; Examples include ether esters such as glycol methyl ether acetate, and lactones such as γ-butyrolactone, and these can be used alone or in combination.

  Moreover, there is no restriction | limiting in particular in the usage-amount of a polymerization solvent, However, Usually, it is 0.5-20 weight part with respect to 1 weight part of monomers, Preferably it is 1-10 weight part. If the amount of the solvent used is too small, the monomer may precipitate or become too viscous to keep the polymerization system uniform, and if it is too much, the conversion rate of the monomer is insufficient or the copolymer In some cases, the molecular weight cannot be increased to a desired value.

  The preparation temperature of the solution containing the monomer or the holding temperature before heating or dropping is such that when the monomer is dissolved and the monomer and the polymerization initiator or chain transfer agent coexist during the holding time, the polymerization initiator or chain transfer agent Select a temperature that does not decompose or precipitate. Specifically, when a polymerization initiator is allowed to coexist in a solution containing a monomer, the temperature of the solution is usually, for example, 50 ° C. or lower, preferably 40 ° C. or lower, in order to prevent decomposition of the polymerization initiator. On the other hand, when the polymerization initiator does not coexist in the solution containing the monomer, it is preferable to prepare or store the monomer at a higher temperature because the solubility of the monomer is improved and a solution with a higher concentration can be obtained. However, in the case of holding in a heated state for a long time, if the temperature is high, the polymerization occurs even in the presence of a polymerization inhibiting component, so the holding temperature is preferably 50 ° C. or less. The concentration of the monomer in the solution containing the monomer is usually selected from the range of 5 to 100% by weight, preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight.

  The polymerization reaction conditions are not particularly limited, but generally the reaction temperature is about 60 ° C. to 100 ° C., and the reaction time varies depending on the polymerization method, but cannot be specified unconditionally. For example, in the case of batch polymerization, the polymerization temperature is reached. The subsequent reaction time is selected between 1 and 24 hours, preferably between 2 and 12 hours. In the case of dripping polymerization, it is preferable that the dripping time is longer because the monomer composition, concentration and radical concentration in the polymerization system can be kept constant. If the dropping time is too long, it is not preferable from the viewpoint of production efficiency per hour and stability of the monomer in the dropping solution. Therefore, the dropping time is selected between 0.5 and 20 hours, preferably between 1 and 10 hours. Since unreacted monomer remains after the completion of the dropwise addition, it is preferable to age while maintaining the polymerization temperature for a certain time. The aging time is selected within 8 hours, preferably from 1 to 6 hours.

  The polymerization reaction solution obtained by the above polymerization reaction is brought into contact with a poor solvent to precipitate a solid (hereinafter referred to as reprecipitation), and the solution portion is removed by a method such as filtration (hereinafter referred to as reprecipitation purification step). ) And, if necessary, the obtained solid is added with a poor solvent or a mixed solvent of a poor solvent and a good solvent to wash the solid, unreacted monomer, oligomer, polymerization initiator, chain transfer agent, and these It can be purified by a step of removing a solution portion containing impurities such as a coupling product by a method such as filtration (hereinafter referred to as a washing purification step). In addition, after drying the obtained solid substance as needed and redissolving with a solvent containing a good solvent, the reprecipitation purification step may be repeated again. Similarly, the obtained solid substance may be used as necessary. And drying, and the washing and purification step using a poor solvent or a mixed solvent of a poor solvent and a good solvent may be repeated.

The good solvent used in each step is not particularly limited as long as it is a solvent that dissolves unreacted monomers, oligomers, polymerization initiators, chain transfer agents and their coupling reaction products including copolymers, but management of the production process. In addition, the same polymerization solvent as mentioned above is preferable. The poor solvent is not particularly limited as long as it is a solvent for precipitating the copolymer, and examples thereof include water; alcohols such as methanol and isopropanol; saturated hydrocarbons such as hexane and heptane, and mixed solvents thereof. be able to. In each step, a good solvent or a poor solvent is used alone, and in order to moderately control the solubility in a copolymer, monomer, oligomer, polymerization initiator, chain transfer agent, and their coupling products, A solvent and a poor solvent can also be mixed and used.

In selecting the type and amount of solvent in the reprecipitation purification step and the washing purification step, and the number of repetitions of each purification step, the residual monomer content is 1% or less, taking into account the solubility of the copolymer and impurities at the set temperature. In particular, it is preferable to select a condition such that it is preferably 0.5% or less, more preferably 0.2% or less. Usually, in order to remove impurities to such a concentration or less, the reprecipitation purification step is performed once, and the washing purification step is preferably performed once or more, more preferably twice or more.

  The copolymer thus purified can be dried and taken out as a powder, or can be taken out again as a solution by adding a good solvent before or after drying. As the good solvent used for re-dissolution, those mentioned as the polymerization solvent can be used similarly. The solution after re-dissolution is passed through a filter having micropores with an average pore size of 0.5 μm or less, preferably 0.1 μm or less, in order to remove extremely fine solids, insoluble foreign matters or metals. It is preferable to do.

  The copolymer obtained by the production method of the present invention has a content of a high molecular weight component (high polymer) having a molecular weight of 100,000 or more in a molecular weight distribution measured by gel permeation chromatography (GPC) of 0.1%. It is extremely low in the following, has excellent solubility in solvents and storage stability, can reduce the occurrence of resist pattern defects, and is useful as a film-forming polymer for semiconductor lithography. .

  When the obtained copolymer is used as a polymer for forming a coating film for semiconductor lithography, the solvent for forming the coating film is supplied to the copolymer solution after purification, and the other solvent used during the purification is reduced under reduced pressure. It can be finished into a solution for forming a coating film by distilling off the solution. The solvent for forming the coating film is not particularly limited as long as it dissolves the copolymer. However, usually considering the boiling point, the influence on the semiconductor substrate and other coating films, and the absorption of radiation used in lithography. Selected. Examples of solvents generally used for coating film formation include solvents such as propylene glycol methyl ether acetate, ethyl lactate, propylene glycol monomethyl ether, methyl amyl ketone, γ-butyrolactone, and cyclohexanone. Is not particularly limited, but is usually in the range of 1 to 20 parts by weight per 1 part by weight of the copolymer.

  When the copolymer is used as a resist polymer, the coating film-forming solution is further added with a radiation-sensitive acid generator and an acid such as a nitrogen-containing compound for preventing the diffusion of acid to a portion not exposed to radiation. A diffusion control agent can be added to finish the resist composition. As the radiation-sensitive acid generator, those generally used as a resist raw material such as an onium salt compound, a sulfone compound, a sulfonic acid ester compound, a sulfonimide compound, and a disulfonyldiazomethane compound can be used.

  Further, if necessary, compounds commonly used as resist additives such as dissolution inhibitors, sensitizers and dyes can be added to the resist composition, and each component in the resist composition (resist The mixing ratio of (except for the solvent) is not particularly limited, but generally ranges from 10 to 50% by mass of the polymer, 0.1 to 10% by mass of the radiation sensitive acid generator, and 0.001 to 10% by mass of the acid diffusion controller. Selected from.

  Further, when the obtained copolymer is used as an antireflection film, it is used alone or mixed with bifunctional or higher functional isocyanates, amines, epoxides or the like capable of crosslinking between polymers.

EXAMPLES Next, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples. In Examples,% indicating concentration is based on mass unless otherwise defined, except for the content of high polymer (%: area percentage). Further, the polymerization inhibitor and dissolved oxygen in the monomer solution subjected to the polymerization reaction were quantified, the high polymer in the obtained copolymer was quantified, and the storage stability was evaluated by the following methods.
(1) Quantification method of amount of polymerization inhibitor The concentration of the polymerization inhibitor in the monomer solution was quantified by HPLC. Analysis conditions and quantification methods are as follows.

Equipment: LC-10AD manufactured by Shimadzu Corporation
Detector: UV254nm
Column: GL Science Inertsil ODS-3V
Mobile phase: Acetonitrile / water = 9/1 (volume ratio)
Sample: A sample was prepared by dissolving 0.1 g of a monomer solution in 1 ml of acetonitrile.
Quantification: Quantified by internal standard method using bisphenol A as internal standard substance.

(2) Method for quantifying dissolved oxygen content The dissolved oxygen content of the monomer solution was measured with a dissolved oxygen meter. The measurement apparatus and measurement conditions are as follows.
Equipment: Orbis Fair model 3650
Measurement conditions: temperature 25-30 ° C., liquid flow rate 50 ml / min

(3) Method for quantifying high polymer The high polymer in the copolymer was quantified by GPC. Analysis conditions and quantification methods are as follows.
Equipment: Tosoh GPC8020
Detector: Differential refractive index (RI) detector Column: Showa Denko KF-804L (x3)
Sample: The polymerization solution after completion of the polymerization was sampled, and diluted with tetrahydrofuran so that the polymer concentration became 1% to prepare a sample.
Quantitation: on GPC, the sample was 15μl injection, The peak area _{A p} of the polymer of interest, then the sample was 150μl injected to determine the area _{A h} of the high polymer peak. From this result, the high polymer content (%) in the polymer was calculated based on the following calculation formula (2).
A _h
High polymer content (%) = ―――――――――― × 100… (2)
(A _p × 10 + A _h )

(4) Copolymer Storage Stability Evaluation Method A 15% propylene glycol methyl ether acetate (hereinafter referred to as “PGMEA”) solution of the copolymer was filtered through a 0.05 μm membrane filter and allowed to reach room temperature for 3 months. The particles in the liquid after storage were measured.
Equipment: KS-40B manufactured by Rion
Evaluation: A case where the number of foreign matters having a particle size of 0.2 μm or more is less than 100 / ml is indicated as ◯, and a case where the particle size is 1000 / ml or more is indicated as ×.

In a monomer solution preparation tank maintained in a nitrogen atmosphere, 5500 g of methyl ethyl ketone (hereinafter referred to as “MEK”), 2080 g of 5-acryloyloxy-2,6-norbornanecarbolactone (hereinafter referred to as “NLA”), 2-ethyl- 2480 g of 2-adamantyl methacrylate (hereinafter referred to as “EAM”), 80 g of azobisisobutyronitrile (hereinafter referred to as “AIBN”) as a polymerization initiator, and 4-methoxyphenol (hereinafter referred to as “polymerization inhibitor”). (Indicated as “MEHQ”.) 50 mg was charged and dissolved, and a monomer solution was prepared and kept at 25-30 ° C. When the amount of MEHQ was determined by sampling the monomer solution, it was 27 mol ppm with respect to the monomer and 0.11 mol% with respect to the polymerization initiator. Further, when the amount of dissolved oxygen in the monomer solution was quantified, it was 166 mol ppm with respect to the monomer. The measurement results of the polymerization inhibitor and dissolved oxygen are summarized in Table 1.

Next, 3500 g of MEK was charged into a polymerization tank maintained in a nitrogen atmosphere and heated to 80 ° C. while stirring, and then the monomer solution was supplied into the polymerization tank maintained at 80 ° C. for 4 hours to be polymerized. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out. The obtained polymerization solution was added dropwise to 70 kg of hydrous methanol to precipitate a polymer, followed by filtration. The obtained wet cake was washed with 70 kg of methanol and filtered, then redissolved in MEK, and passed through a filter 40QSH made by Cuno. Subsequently, PGMEA was thrown in while purging MEK by heating under reduced pressure to replace the solvent, and a PGMEA solution containing 15% polymer was prepared. Table 2 shows the composition of the obtained polymer, the weight average molecular weight (Mw), the molecular weight distribution (Mw / Mn), the high polymer content, and the storage stability evaluation results of the PGMEA solution.

  MEK 9000 g, NLA 2080 g, EAM 2480 g, 3-hydroxy-1-adamantyl methacrylate (hereinafter referred to as “HAM”) 2220 g, AIBN 110 g as a polymerization initiator, and MEHQ 100 mg as a polymerization inhibitor are charged in a monomer solution preparation tank maintained in a nitrogen atmosphere. The monomer solution was prepared and kept at 25-30 ° C. The measurement results of the polymerization inhibitor and dissolved oxygen in the monomer solution are summarized in Table 1.

  Next, 5000 g of MEK was charged into a polymerization tank maintained in a nitrogen atmosphere and heated to 80 ° C. while stirring, and then the monomer solution was supplied into the polymerization tank maintained at 80 ° C. for 4 hours for polymerization. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out. The obtained polymerization solution was dropped into 100 kg of hydrous methanol to precipitate a polymer, followed by filtration. The obtained wet cake was washed with 100 kg of methanol and filtered, then redissolved in MEK, and passed through a CUENO filter 40QSH. Subsequently, PGMEA was thrown in while purging MEK by heating under reduced pressure to replace the solvent, and a PGMEA solution containing 15% polymer was prepared. Table 2 shows the composition of the obtained polymer, the weight average molecular weight (Mw), the molecular weight distribution (Mw / Mn), the high polymer content, and the storage stability evaluation results of the PGMEA solution.

  MEK 7700 g, 5-methacryloyloxy-2,6-norbornanecarbolactone (hereinafter referred to as “NLM”) 2220 g, EAM 2480 g, methacrylic acid (hereinafter referred to as “MA”) 90 g in a monomer solution preparation tank maintained in a nitrogen atmosphere. Then, 80 g of AIBN as a polymerization initiator and 50 mg of MEHQ as a polymerization inhibitor were charged and dissolved, and a monomer solution was prepared and kept at 25 to 30 ° C. The measurement results of the polymerization inhibitor and dissolved oxygen in the monomer solution are summarized in Table 1.

Next, 3300 g of MEK was charged into a polymerization tank maintained in a nitrogen atmosphere and heated to 80 ° C. while stirring, and then the monomer solution was supplied into the polymerization tank maintained at 80 ° C. for 4 hours to be polymerized. After the completion of the supply, the polymerization temperature was kept at 80 ° C. for 2 hours, and the mixture was cooled to room temperature and the polymerization solution was taken out. The obtained polymerization solution was dropped into 80 kg of water-containing methanol to precipitate a polymer, followed by filtration. The obtained wet cake was washed with 80 kg of methanol and filtered, then redissolved in MEK and passed through a filter 40QSH made by Cuno. Subsequently, PGMEA was thrown in while purging MEK by heating under reduced pressure to replace the solvent, and a PGMEA solution containing 15% polymer was prepared. Table 2 shows the composition of the obtained polymer, the weight average molecular weight (Mw), the molecular weight distribution (Mw / Mn), the high polymer content, and the storage stability evaluation results of the PGMEA solution.

  This was carried out in the same manner as in Example 1 except that the monomer solution preparation tank was kept in an air atmosphere and MEHQ was not added. The results are shown in Tables 1 and 2.

It implemented like Example 1 except the addition amount of MEHQ having been 5 g. The results are shown in Tables 1 and 2.
Comparative Examples 1-3

It implemented like Example 1-3 except not having added MEHQ. The results are shown in Table 1 and Table 2.
It was shown to. In addition, the polymerization inhibitor (MEHQ) of the order of several ppm detected in Example 4 and Comparative Examples 1 to 3 in which no polymerization inhibitor was added is the one used in the production process of the monomer used. It is thought that there is.

As is apparent from this result, a method in which a polymerization inhibitor is not added to the monomer and the monomer solution preparation tank is maintained in a nitrogen atmosphere produces a high polymer, and insoluble foreign matter grows during the storage period. Admitted. On the other hand, in the present invention, by allowing a polymerization inhibitor or oxygen to coexist in a certain amount or more as a polymerization inhibitor component in a solution containing a monomer, a high polymer is not generated and a resist polymer having excellent storage stability can be obtained. I understand that.

  INDUSTRIAL APPLICABILITY According to the present invention, it is suitably used for coating film forming compositions such as resist film forming compositions used for fine pattern formation in semiconductor manufacturing, multilayer resist underlayer film forming compositions, and antireflection film forming compositions. In addition, a method for producing a copolymer for semiconductor lithography (which does not contain a high polymer and has very few resist pattern defects when used in semiconductor lithography) is provided.

Claims (5)

At least a repeating unit (A) represented by the general formulas (1) to (8) having a structure that is decomposed by an acid and becomes soluble in an alkali developer, and a polar group for enhancing adhesion to a semiconductor substrate A method for producing a copolymer for semiconductor lithography having a repeating unit (B), wherein a solution containing two or more monomers having an ethylenic double bond giving the repeating unit is dropped into a heated solvent. When producing a copolymer for semiconductor lithography by radical polymerization with a polymerization inhibitor as a polymerization inhibitor component in a solution containing the monomer before dropping, a polymerization inhibitor of 20 mol ppm to 5000 mol ppm with respect to the monomer (however, Excluding nitrogen-containing stable free radical agents) or coexisting with 400 mol ppm or more and 10,000 mol ppm or less oxygen. Method for producing a copolymer for semiconductor lithography, characterized in that to the solution dropwise to the solvent heating the radical polymerization.
General formula (1)

(In the formula, R ₁ represents a hydrogen atom or a methyl group, and —OR is not bonded to the ortho position.)
General formula (2)

(In the formula, R ₂ represents a hydrogen atom, a methyl group or a trifluoromethyl group.)
General formula (3)

(In the formula, _one of Re ₁ and Re ₂ represents a hydrogen atom, and the other represents a —C (═O) OR group.)
General formula (4)

(In the formula, R ₄ represents a hydrogen atom or a trifluoromethyl group.)
General formula (5)

(In the formula, R ₅ represents a methyl group.)
General formula (6)

(In the formula, R ₆ represents a hydrogen atom.)
General formula (7)

(In the formula, R ₇ represents a hydrogen atom or a trifluoromethyl group.)
General formula (8)

{In the formulas (1) to (8), when R is an acid dissociable group, it represents a repeating unit (A), and when it is a polar group, it represents a repeating unit (B), and R as an acid dissociable protecting group is tert-butyl group, tert-amyl group, 1-methyl-1-cyclopentyl group, 1-ethyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 2-methyl- 2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 8-methyl-8-tricyclo [5.2.1. 0 ^2,6] decanyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6] decanyl group, 8-methyl-8-tetracyclo [4.4.0.1 ^{2, 5} .1 ^7,10 ] dodecanyl group, 8-ethyl-8-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl saturated hydrocarbon group such as a group; a 1-methoxyethyl group, 2-ethoxyethyl group, 1-an iso-propoxyethyl group, 1-n-butoxyethyl group, 1 -Tert-butoxyethyl group, 1-cyclopentyloxyethyl group, 1-cyclohexyloxyethyl group, 1-tricyclo [5.2.1.0 ^2,6 ] decanyloxyethyl group, 1-methoxymethyl group, 2- Ethoxymethyl group, 1-iso-propoxymethyl group, 1-n-butoxymethyl group, 1-tert-butoxymethyl group, 1-cyclopentyloxymethyl group, 1-cyclohexyloxymethyl group, 1-tricyclo [5.2. 1.0 ^2,6] decanyl oxymethyl group, a tert- butoxycarbonyl radical, R as the polar group, .gamma.-butyrolactone, .gamma.-valerolactone, .delta. Bas Rorakuton, 1,3 cyclohexane lactone, 2,6-norbornanecarbolactone, 4-oxa-tricyclo [5.2.1.0 ^{2, 6]} decan-3-one, mevalonate δ- lactone, hydroxymethyl group , A hydroxyethyl group, a hydroxypropyl group, and a 3-hydroxy-1-adamantyl group. }   The solution containing the monomer before dropping contains a polymerization initiator, and the amount of the polymerization inhibitor coexisting in the solution is 0.1 mol% or more and 20 mol% or less with respect to the polymerization initiator in the solution. Item 2. A method for producing a copolymer for semiconductor lithography according to Item 1.   The polymerization inhibitor is one or more compounds selected from hydroquinone, benzoquinone, catechol, phenothiazine, N-nitrosophenylhydroxyamine, 2,2,6,6, -tetramethylpiperidine-1-oxyl free radical and derivatives thereof. A method for producing a copolymer for semiconductor lithography according to claim 1 or 2.   The solution containing the monomer before dropping contains a polymerization initiator, and the amount of oxygen coexisting in the solution is 2 mol% or more and 50 mol% or less with respect to the polymerization initiator in the solution. The manufacturing method of the copolymer for semiconductor lithography of description.   In producing a copolymer for semiconductor lithography by radical polymerization of two or more monomers having an ethylenic double bond in the presence of a polymerization initiator in a polymerization solvent, as a polymerization inhibitor component in a solution containing the monomer, A method for producing a copolymer for semiconductor lithography in which a polymerization inhibitor of 20 mol ppm or more or 400 mol ppm or more of oxygen coexists with respect to a monomer and radically polymerizes with this solution, wherein the solution containing the monomer is a polymerization initiator A method for producing a copolymer for semiconductor lithography, wherein the amount of oxygen coexisting in the solution is 2 mol% or more based on the polymerization initiator in the solution.