JP2004231950A - Copolymer for resist and method for producing the same, resist composition and pattern production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the high sensitivity and / or resolution of a resist from being impaired when used in DUV excimer laser lithography or electron beam lithography, etc., to suppress solubility in a resist solvent, to suppress microgel formation in a resist solution, Provided is a resist copolymer which is excellent in resist film surface roughness after dry etching treatment, resist pattern uprightness due to heat treatment, and line edge roughness.
SOLUTION: This is a resist copolymer containing a monomer unit having an alicyclic skeleton or a monomer unit having a lactone skeleton, wherein the resist copolymer has an acrylic monomer unit in an amount of 20 mol. % Or more and 68 mol% or less.
[Selection diagram] None

Description

  The present invention relates to a copolymer for a resist and a method for producing the same, a resist composition containing the copolymer for a resist, and a method for producing a pattern, particularly for a chemically amplified resist suitable for fine processing using an excimer laser or an electron beam. It relates to a copolymer.

  In recent years, in the field of fine processing in the manufacture of semiconductor elements and liquid crystal elements, miniaturization has rapidly progressed due to advances in lithography technology. As a method of miniaturization, a shorter wavelength of an exposure light source is generally used, and specifically, the ultraviolet light represented by the conventional g-line and i-line has been changed to DUV (Deep Ultra Violet).

Currently, KrF excimer laser (248 nm) lithographic technique has been introduced to the market, it is about to be introduced ArF excimer laser (193 nm) lithographic technique which attained further short Nagaka is, F ₂ excimer laser as a further next generation technology (157 nm) lithography technology is being studied. Also, electron beam lithography, which is a type of lithography slightly different from the above, has been energetically studied.

  International Business Machines (IBM) has proposed a "chemically amplified resist" as a high-resolution resist for such a short-wavelength light source or electron beam. It is being advanced.

In addition, when the wavelength of the light source is shortened, the structure of the resin used for the resist must be changed. In KrF excimer laser lithography, polyhydroxystyrene having a high transparency to 248 nm or one in which a hydroxyl group thereof is protected by an acid dissociable, dissolution inhibiting group was used. In ArF excimer laser lithography, the resin was 193 nm. , The transparency is insufficient and almost unusable, so that an acrylic resin or a cycloolefin resin transparent at 193 nm is attracting attention. As such an acrylic resin, for example, a copolymer of a (meth) acrylate having an adamantane skeleton in an ester portion and a (meth) acrylate having a lactone skeleton in an ester portion is disclosed in Patent Documents 1 and 2. And so on. In addition, "(meth) acrylate" is a general term for acrylate and methacrylate.
JP-A-10-319595 JP, 10-274852, A In addition, in order to respond to the thinning of a resist by further thinning of lithography technology in recent years, a monomer having a polycyclic lactone skeleton in which an alicyclic structure is introduced into a lactone skeleton was used. Copolymers for resists are described in Patent Literature 3, Patent Literature 4, and the like. JP-A-2000-26446 However, when all or most of the monomer units constituting the copolymer for resist have an alicyclic structure and all of the monomer units are methacrylic, a dry etching treatment is performed. The subsequent roughening of the surface of the resist film often causes pinholes in the film, causing problems such as disconnection and defects in the circuit when transferring the pattern to a substrate to be processed such as a silicon substrate. It may be a factor that lowers the yield in the process. In addition, the copolymer for resist in the resist solution once dissolved uniformly aggregates with time, and an insoluble component called microgel is generated to cause omission in the resist pattern. Problems such as disconnection and defects may occur, which may reduce the yield in the semiconductor manufacturing process.

  Further, when all or most of the monomer units constituting the copolymer for resist have an alicyclic structure, and all of the monomer units are acrylic, distortion of the resist pattern is caused by heat treatment after exposure. In some cases, the pattern cannot be transferred to a substrate to be processed such as a silicon substrate by dry etching.

  On the other hand, in a method for producing a resist copolymer by copolymerizing a monomer having an alicyclic skeleton and a monomer having a lactone skeleton as described above, for example, in Patent Document 1 and Patent Document 3, A method is employed in which a monomer component, a polymerization solvent, a polymerization initiator, and, in some cases, a chain transfer agent (molecular weight modifier) are charged into a polymerization apparatus at a time. However, in this method, there is a concern that the composition distribution may be widened due to the deviation of the copolymerization monomer ratio in the late stage of the polymerization and the use of a monomer component having a greatly different copolymerization reactivity ratio.

  Therefore, the copolymer for a resist produced by such a method tends to have insufficient solubility in a solvent when preparing a resist solution, and a long time is required for dissolution, or an insoluble component is generated. As a result, the preparation of the resist solution is hindered, for example, the number of manufacturing steps is increased. In addition, the copolymer for resist in the resist solution, once dissolved uniformly, agglomerates with time, and insoluble components called microgels are generated, causing the resist pattern to drop out. May occur, which may lower the yield in the semiconductor manufacturing process. In addition, patterning with an excimer laser and subsequent development processing cause side wall roughness (hereinafter also referred to as “line edge roughness”) of a resist pattern, resulting in non-uniform circuit width, circuit breakage and defects. This may cause a decrease in the yield in the semiconductor manufacturing process as in the case of the microgel.

  Thus, without impairing high sensitivity and / or resolution of the resist industrially, solubility in the resist solvent, suppression of microgel formation in the resist solution, reduction of resist film surface roughness after dry etching treatment, At present, there is a demand for a resist copolymer having excellent resist pattern uprightness and line edge roughness by heat treatment.

  The present invention has been made in order to solve the above-described problems of the prior arts, and has an object to achieve high sensitivity and / or high sensitivity of a resist when used in DUV excimer laser lithography or electron beam lithography. Or, without impairing the resolution, the solubility in the resist solvent, the suppression of microgel formation in the resist solution, the reduction of the resist film surface roughness after dry etching treatment, the uprightness of the resist pattern by heat treatment, the line edge roughness An object of the present invention is to provide an excellent copolymer for resist.

  The present inventors have studied diligently to achieve the above-mentioned object, and particularly, to the main chain structure of the copolymer for resist, the stereoregularity, the copolymer chain structure and its distribution, or the fine structure such as the terminal group structure. Focusing on the results, the main chain structure and copolymer chain distribution of the copolymer for resist showed solubility in the resist solvent, suppressed the formation of microgels in the resist solution, and reduced the surface roughness of the resist film after dry etching. It has been found that the heat treatment significantly affects the uprightness of the resist pattern and the line edge roughness, and the present invention has been completed.

  That is, a first aspect of the present invention is a copolymer for resist containing a monomer unit having an alicyclic skeleton, wherein the copolymer for resist contains not less than 20 mol% and not more than 68 mol% of an acrylic monomer unit. % Or less.

The monomer unit having an alicyclic skeleton is preferably at least one monomer unit selected from the following formulas (A1) to (A4) and (A10).

(In the formulas (A1) to (A4) and (A10), R represents a hydrogen atom or a methyl group, and R ¹ , R ² , and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms. ⁴ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ^{41 to} R ⁴⁴ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or a carbon atom. R ^{45 to} R ⁴⁸ each independently represent a hydrogen atom, —R ⁵⁰ —CN, —R ⁵¹ —CH (CN) ₂ , —R ⁵² —COO. —R ⁵³ , — (CH ₃ ) _m —C (CF ₃ ) ₂ —OH, wherein R ⁴⁹ is a hydrogen atom, an alkoxy group having 1 to 3 carbon atoms which may have a branch, a cyano group Or an ester group having 1 to 6 carbon atoms, and R ^{50 to} R ⁵² each independently represent a carbon atom. R ⁵³ represents an alkylene group which may have a branch or a single bond, and R ⁵³ represents an acid-eliminable group, wherein the acid-eliminable group is decomposed or eliminated by the action of an acid. .X and Y refer to a radicals are each _{independently, -O -, - CH 2 -} , - CH 2 CH 2 -. shows a .m is an integer of 0 to 6 also, p is 0 R ⁵ , R ⁶ , and R ⁷ each independently represent a hydrogen atom or a hydroxyl group, R ¹⁰¹ represents an alkyl group having 1 to 3 carbon atoms, and r represents an integer of 0 to 2. .)
Further, it is preferable that the resist copolymer further contains a monomer unit having a lactone skeleton.

  A second aspect of the present invention is a resist copolymer containing a monomer unit having a lactone skeleton, wherein the resist copolymer contains an acrylic monomer unit in an amount of 20 mol% to 68 mol%. And a copolymer for resists.

The monomer unit having a lactone skeleton is preferably at least one monomer unit selected from the following formulas (A5) and (A6).

(In the formula (A5), R represents a hydrogen atom or a methyl group, and R ⁶¹ and R ⁶² each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group, or a carbon number. A ¹ and A ² each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or 1 to 6 carbon atoms; 6 represents a carboxy group esterified with an alcohol, or A ¹ and A ² together represent —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— ( CH ₂ ) _q — (q represents an integer of 1 to 6)], wherein X ⁵ is a hydroxyl group, a carboxy group, an acyl group having 1 to 6 carbon atoms, or an alcohol having 1 to 6 carbon atoms as a substituent. Esterified carboxy group, shea A linear or branched alkyl group having 1 to 6 carbon atoms, which may have at least one group selected from the group consisting of a group and an amino group, a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, carbon Represents an alkoxy group having 1 to 6 carbon atoms, a carboxy group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group or an amino group, and n5 represents an integer of 0 to 4. In the case where n5 is 2 or more, Also includes having a plurality of different groups as X ⁵ .

In the formula (A6), R represents a hydrogen atom or a methyl group, and R ⁶³ and R ⁶⁴ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or a 1 carbon atom. represents esterified carboxy group at 6 alcohol, a ^3, a ⁴ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, hydroxy group, the number carboxy group or a carbon 1-6 Represents a carboxy group esterified with an alcohol of the formula (I), or A ³ and A ⁴ are taken together to form —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— (CH ₂ ) _r- (r represents an integer of 1 to 6)]. X ⁶ is at least one selected from the group consisting of a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, a carboxy group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group and an amino group. A linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol, and n6 represents an integer of 0 to 4. Incidentally, also includes having a plurality of different groups as X ⁶ in the case of n6 is 2 or more. )
The copolymer for resist has a total content of the monomer unit having an alicyclic skeleton and the monomer unit having a lactone skeleton of 80 mol% of all the monomer units constituting the copolymer for resist. The above is preferable.

  The third aspect of the present invention is any one of the above-mentioned methods for producing a resist copolymer, in which a solvent is previously charged into a polymerization vessel, and the polymerization vessel is heated to a predetermined polymerization temperature, and then a monomer and a polymerization start are started. A method for producing a copolymer for resists, which comprises dropping a monomer solution, in which an agent and, in some cases, a molecular weight modifier are dissolved in an organic solvent, into a polymerization vessel.

  The fourth aspect of the present invention is a method for producing any of the above resist copolymers, in which a part of the monomer is charged in a polymerization vessel in advance, and the polymerization vessel is heated to a predetermined polymerization temperature to carry out polymerization. After the start, the remaining monomer and polymerization initiator, in some cases, a monomer solution in which a molecular weight modifier is dissolved in an organic solvent, a resist copolymer characterized by being dropped into a polymerization vessel It is a manufacturing method.

  In the above method for producing a resist copolymer, it is preferable that at least two or more types of monomer solutions having different monomer composition ratios be independently dropped into a polymerization vessel.

  A fifth aspect of the present invention is a resist composition comprising any one of the above copolymers for resist.

  A sixth aspect of the present invention is a chemically amplified resist composition comprising any of the above resist copolymers and a photoacid generator.

  In a seventh aspect of the present invention, at least a step of applying the resist composition of the fifth or sixth aspect on a substrate to be processed, a step of exposing to light having a wavelength of 250 nm or less, and a heat treatment as required And then developing.

  In the above pattern manufacturing method, it is preferable that the light used for exposure is ArF excimer laser light.

  According to an eighth aspect of the present invention, at least a step of applying the resist composition of the fifth or sixth aspect on a substrate to be processed, a step of exposing with an electron beam, and, if necessary, a heat treatment, followed by development. And a pattern manufacturing method.

  The copolymer for resists and the resist composition of the present invention have high solubility and / or resolution in a resist solvent without impairing high sensitivity and / or resolution, suppression of microgel formation in a resist solution, and a resist film after a dry etching treatment. It is excellent in reduction of surface roughness, uprightness of a resist pattern by heat treatment, and line edge roughness, and can stably form a high-accuracy fine resist pattern. Therefore, the copolymer for resist and the resist composition of the present invention can be suitably used for DUV excimer laser lithography or electron beam lithography, particularly lithography using an ArF excimer laser (193 nm).

  The copolymer for resist of the present invention contains at least one monomer unit selected from a monomer unit having an alicyclic skeleton and a monomer unit having a lactone skeleton.

The acrylic monomer unit of the present invention is a monomer unit having the following formula (M). In order to introduce such a unit into the copolymer for resist, copolymerization may be carried out using a (co) polymerizable monomer represented by the following formula (m).

  If the acrylic monomer unit in the copolymer for resist is at least 20 mol%, preferably at least 30 mol%, and more preferably at least 35 mol%, large roughness of the resist film surface after dry etching treatment, It is possible to suppress problems such as disconnection and defects of a circuit at the time of pattern transfer to a substrate to be processed such as a silicon substrate due to pinholes existing in the inside. Also, the resist copolymer in the resist solution once dissolved in the resist solution is aggregated with time, resulting in the generation of insoluble components called microgels, the removal of the resist pattern, and the disconnection of the circuit during pattern transfer. And defects such as defects.

  On the other hand, if the acrylic monomer unit in the copolymer for resist is 68 mol% or less, preferably 65 mol% or less, and more preferably 60% or less, the resist pattern may be distorted or collapsed by heat treatment after exposure, and The problem of pattern transfer failure due to dry etching on a substrate to be processed such as a silicon substrate can be suppressed.

  The acrylic monomer unit in the copolymer for resist does not need to be composed of only a monomer unit having a single alicyclic skeleton or only a monomer unit having a single lactone skeleton. It may be a mixture of a monomer unit having a cyclic skeleton and a monomer unit having a lactone skeleton, or a mixture of these and an acrylic monomer unit having another skeleton.

  The monomer unit having an alicyclic skeleton is a monomer unit having a structure having at least one cyclic saturated hydrocarbon. In order to introduce such a unit into the copolymer for resist, for example, copolymerization may be performed using a monomer having an alicyclic skeleton. Hereinafter, a monomer into which a monomer unit having an alicyclic skeleton can be introduced into a polymer is referred to as a “monomer having an alicyclic skeleton”.

  Examples of the monomer having the alicyclic skeleton include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, tetracyclododecyl (meth) acrylate, Dicyclopentadienyl (meth) acrylate and derivatives of these compounds having a substituent on the alicyclic ring are preferred. In the present invention, “(meth) acrylate” is a general term for acrylate and methacrylate.

  Copolymers for resists containing monomer units having an alicyclic skeleton have excellent dry etching resistance, and excellent sensitivity when these monomer units contain a protecting group which can be eliminated by acid. Having. Furthermore, when these monomer units contain a hydroxyl group, they have excellent resist pattern shape stability.

  The monomer having an alicyclic skeleton can be used alone or in combination of two or more as necessary.

  When copolymerizing a monomer having an alicyclic skeleton, the monomer having an alicyclic skeleton is preferably used in a range of 10 to 90 mol%, and more preferably 30 to 70 mol%, based on the whole monomer components. % Is more preferably used.

  The more the monomer having an alicyclic skeleton, the more the dry copolymerization resistance of the obtained copolymer for resist and its resin composition is improved, and the less the monomer, the stronger the properties of other monomers tend to appear. When the other monomer is a monomer having a lactone skeleton, the smaller the number of monomers having an alicyclic skeleton, the better the adhesion.

In the formula (A1), examples of the alkyl group having 1 to 3 carbon atoms for R ¹ include a methyl group, an ethyl group, a propyl group, and an isopropyl group. As specific examples of the monomer into which the monomer unit can be introduced, the following formulas (1-1) to (1-4)

Is mentioned. Among them, the monomers represented by the formulas (1-1) to (1-4) are preferable from the viewpoint of excellent sensitivity and resolution when used as a resist composition. R represents a hydrogen atom or a methyl group.

In the formula (A2), examples of the alkyl group having 1 to ³ carbon atoms for R ² and R ³ include a methyl group, an ethyl group, a propyl group, and an isopropyl group. As specific examples of the monomer into which this monomer unit can be introduced, the following formulas (2-1) to (2-10)

Is mentioned. Among them, the monomer represented by the above formula (2-1) is preferable from the viewpoint of excellent sensitivity and resolution when used as a resist composition. R represents a hydrogen atom or a methyl group.

As specific examples of the monomer into which the monomer unit of the formula (A3) can be introduced, the following formulas (3-1) to (3-164)

Is mentioned. Among them, from the viewpoint of excellent sensitivity and resolution when used as a resist composition, the above formulas (3-1), (3-2), (3-5), (3-6), and (3-6) Formulas (3-9) to (3-20), Formulas (3-25) to (3-28), Formulas (3-37) to (3-40), Formulas (3-49) to (3-49) 3-52), Formulas (3-61) to (3-64), Formulas (3-73) to (3-76), Formulas (3-85) to (3-88), Formula (3-85) 3-97) to (3-100), the monomers represented by the formulas (3-109) to (3-112), the formulas (3-117) to (3-164), and geometric isomers thereof. And optical isomers are preferred. In addition, the monomers represented by the above formulas (3-21) to (3-92) and their geometric isomers, optical isomers, and the like are preferred because of their excellent resist pattern rectangularity when formed into a resist composition. preferable. R represents a hydrogen atom or a methyl group.

Specific examples of the monomer into which the monomer unit of the formula (A4) can be introduced include the following formulas (4-1) to (4-4)

Is mentioned. Above all, a monomer represented by the above formula (4-1) is preferable from the viewpoint of excellent resist pattern rectangularity when formed into a resist composition. R represents a hydrogen atom or a methyl group.

As specific examples of the monomer into which the monomer unit of the formula (A10) can be introduced, the following formulas (10-1) to (10-9)

Is mentioned. Among them, the monomers represented by the formulas (10-2) and (10-5) are preferable from the viewpoint of excellent sensitivity and resolution when used as a resist composition. R represents a hydrogen atom or a methyl group.

  The monomer unit having a lactone skeleton is a monomer unit having a structure having a cyclic saturated hydrocarbon containing a carboxyl group in the ring. In order to introduce such a unit into the copolymer for resist, for example, copolymerization may be performed using a monomer having a lactone skeleton. Further, the monomer unit having a lactone skeleton may further have an alicyclic skeleton. Hereinafter, a monomer into which a monomer unit having a lactone skeleton can be introduced into a polymer is referred to as a “monomer having a lactone skeleton”.

  Examples of the monomer having a lactone skeleton include a (meth) acrylate having a δ-valerolactone ring, a (meth) acrylate having a γ-butyrolactone ring, a (meth) acrylate having a polycyclic lactone, and the like. Derivatives having a substituent on the cyclic saturated hydrocarbon skeleton containing a lactone ring of the compound (1).

  Copolymers for resists containing a monomer unit having a lactone skeleton have excellent adhesion to highly polar surfaces such as metal surfaces, and these monomer units contain a protective group which is released by an acid. Has excellent sensitivity. Furthermore, when these monomer units contain a high carbon density, they have excellent dry etching resistance.

  The monomer having a lactone skeleton can be used alone or in combination of two or more as needed.

  When copolymerizing a monomer having a lactone skeleton, the monomer having a lactone skeleton is preferably used in a range of 10 to 90 mol%, more preferably 30 to 70 mol%, based on the entire monomer components. Mol% range. As the monomer having a lactone skeleton increases, the adhesion of the obtained resist copolymer and its resin composition improves, and as the monomer decreases, the properties of the other monomer tend to appear more strongly. When the other monomer is a monomer having an alicyclic skeleton, and the monomer having a lactone skeleton does not have an alicyclic skeleton, the less the monomer having a lactone skeleton, the better the dry etching resistance. improves.

As specific examples of the monomer into which the monomer unit of the formula (A5) can be introduced, the following formulas (5-1) to (5-11)

Is mentioned.

Among them, the monomer represented by the formula (5-3) is preferable from the viewpoint of solubility in a resist solvent, and the formulas (5-2) and (5-4) are preferable from the viewpoint of dry etching resistance. ), The monomers represented by the formulas (5-5) and (5-9), and geometric isomers and optical isomers thereof are preferable. The monomer represented by the formula (5-3) is preferable, and from the viewpoint of good sensitivity, the monomer represented by the formula (5-9), the formula (5-10) and the formula (5-11) is preferable. Monomers and their geometric isomers and optical isomers are preferred, and the monomers represented by the above formulas (5-6) and (5-8) and their geometric shapes are preferable from the viewpoint of good pattern shape. Isomers and optical isomers are preferred.

As specific examples of the monomer into which the monomer unit of the formula (A6) can be introduced, the following formulas (6-1) to (6-14)

Is mentioned. Among them, from the viewpoint of dry etching resistance, the formula (6-2), the formula (6-4), the formula (6-6), the formula (6-8), the formula (6-9), Monomers represented by the formula (6-10) and the formula (6-11) and geometric isomers and optical isomers thereof are preferable, and from the viewpoint of solubility in a resist solvent, the formula (6- 10) 3), monomers represented by the formulas (6-7), (6-12), (6-13) and (6-14), and geometric isomers and optical isomers thereof The body is preferred.

  When the resist copolymer of the present invention is used for ArF excimer laser lithography, it preferably contains both a monomer unit having an alicyclic skeleton and a monomer unit having a lactone skeleton. In addition, the copolymer for resist of the present invention may contain a monomer unit other than a monomer unit having an alicyclic skeleton and / or a monomer unit having a lactone skeleton. That is, the copolymer for resist of the present invention is a vinyl-based monomer copolymerizable with a monomer having an alicyclic skeleton and / or a monomer having a lactone skeleton (hereinafter referred to as “other vinyl-based monomer”). Monomer ").

  Further, the acrylic monomer unit in the copolymer for resist may be a monomer unit having a single alicyclic skeleton, a monomer unit having a single lactone skeleton, or a single other lactone skeleton. It is not necessary to constitute only the acrylic monomer unit having a skeleton, and a mixture of these monomer units may be used.

Other vinyl monomers that may be included in the resist copolymer of the present invention include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-propyl ( (Meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, methoxymethyl (meth) acrylate, n-propoxyethyl (meth) Acrylate, iso-propoxyethyl (meth) acrylate, n-butoxyethyl (meth) acrylate, iso-butoxyethyl (meth) acrylate, tert-butoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxy -N Propyl (meth) acrylate, 2-hydroxy-n-propyl (meth) acrylate, 4-hydroxy-n-butyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 1-ethoxyethyl (meth) acrylate, 2, 2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoro-n-propyl (meth) acrylate, 2,2,3,3,3-pentafluoro-n-propyl (meth) Acrylate, α- (tri) fluoromethyl acrylate methyl ester, α- (tri) fluoromethyl acrylate ethyl ester, α- (tri) fluoromethyl acrylate 2-ethylhexyl ester, α- (tri) fluoromethyl acrylate-n-propyl ester , Α- (tri) fluoromethyl acrylate-iso- Propyl ester, α- (tri) fluoromethyl acrylate-n-butyl ester, α- (tri) fluoromethyl acrylate-iso-butyl ester, α- (tri) fluoromethyl acrylate-tert-butyl ester, α- (tri) fluoro Methyl acrylate methoxymethyl ester, α- (tri) fluoromethyl acrylate ethoxyethyl ester, α- (tri) fluoromethyl acrylate-n-propoxyethyl ester, α- (tri) fluoromethyl acrylate-iso-propoxyethyl ester, α- (Tri) fluoromethyl acrylate n-butoxyethyl ester, α- (tri) fluoromethyl acrylate-iso-butoxyethyl ester, α- (tri) fluoromethyl acrylate tert-butoxyethyl (Meth) acrylates having a linear or branched skeleton structure such as
Styrene, α-methylstyrene, vinyltoluene, p-hydroxystyrene, 3,5-di-tert-butyl-4-hydroxystyrene, 3,5-dimethyl-4-hydroxystyrene, p-tert-perfluorobutylstyrene, aromatic alkenyl compounds such as p- (2-hydroxy-iso-propyl) styrene;
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride; acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, vinyl chloride, ethylene, vinyl fluoride, fluorine Vinylidene fluoride, tetrafluoroethylene, vinylpyrrolidone and the like.

  These can be used alone or in combination of two or more as needed. In addition, when these monomers contain a protecting group which is eliminated by an acid, excellent sensitivity is obtained.

  Other vinyl monomers can be used as long as the adhesion and dry etching resistance of the obtained resist copolymer are not significantly impaired. Generally, the content is preferably 20 mol% or less based on the whole monomer components.

  In polymerization using a polymerization initiator, a radical form of the polymerization initiator is generated in the reaction solution, and chain polymerization of the monomer proceeds from the radical form.

  The polymerization initiator used for producing the copolymer for resists of the present invention is preferably one that efficiently generates radicals by heat. Examples of such a polymerization initiator include, for example, azo compounds such as 2,2′-azobisisobutyronitrile and dimethyl-2,2′-azobisisobutyrate; 2,5-dimethyl-2,5- Organic peroxides such as bis (tert-butylperoxy) hexane; and the like.

  In the case of producing a resist copolymer for lithography using an ArF excimer laser (193 nm) light source, a copolymer having no aromatic ring in the molecular structure is preferable so as to minimize the light transmittance. Further, in consideration of safety at the time of polymerization, it is preferable that the polymerization initiator has a 10-hour half-life temperature of 60 ° C. or more.

  When producing a copolymer for resist, a chain transfer agent may be used.

  The use of a chain transfer agent has the advantages that the amount of the polymerization initiator can be reduced when producing a low molecular weight resist copolymer, and that the molecular weight distribution of the resist copolymer can be reduced. is there.

  Suitable chain transfer agents include, for example, 1-butanethiol, 2-butanethiol, 1-octanethiol, 1-decanethiol, 1-tetradecanethiol, cyclohexanethiol, 2-methyl-1-propanethiol, 2-mercapto Ethanol and the like can be mentioned.

  In the polymerization reaction, a polymer having a radical at the growth end is generated in the reaction solution.However, if a chain transfer agent is used, the radical at the growth end collides with the chain transfer agent, and the polymer whose growth end is deactivated is generated. Become. On the other hand, the chain transfer agent has a structure having radicals, and the radicals are used as starting points to cause chain polymerization of the monomers again. Therefore, a chain transfer residue exists at the terminal of the obtained polymer.

  When producing a resist copolymer for lithography using an ArF excimer laser (193 nm) light source, a chain transfer agent having no aromatic ring should be used so as to minimize the light transmittance of the resist copolymer. preferable.

  The copolymer for resist of the present invention has excellent solubility in a resist solvent, and by using the copolymer for resist of the present invention, suppression of microgel formation in a resist solution, and resist after dry etching treatment. The present inventors presume as follows about the reason why the surface roughness of the film is reduced and the performance of the resist pattern upright by heat treatment is excellent.

  That is, the conventional copolymer for resist has an alicyclic structure in which all or most of the monomer units constituting the copolymer for resist have an alicyclic structure in order to cope with thinning of the resist due to thinning of the lithography technology. In addition, when all or most of the monomer units are methacrylic, the flexibility of one molecular chain is reduced, resulting in the penetration of the resist solvent into the molecular chain, that is, the solubility in the resist solvent. Was not sufficient, and microgels were formed in the resist solution. Also, when all or most of the monomer units are methacrylic, the glass transition temperature is sufficiently higher than the heat treatment temperature after exposure, so that the molecular chains forming the resist film during heating after exposure are not easily relaxed, and the resist film By performing the dry etching process with the solvent remaining inside, voids in portions occupied by the solvent molecules appeared on the surface, causing surface roughness.

  On the other hand, when all or most of the monomer units were acrylic, the glass transition temperature was lower than the heat treatment temperature after exposure, so that the resist pattern was distorted or collapsed.

  The present invention has solved such a problem by controlling this point.

  As a method for producing the resist copolymer of the present invention, a polymerization method generally called solution polymerization is preferable. The polymerization temperature in the drop polymerization method is not particularly limited, but is preferably in the range of 50 to 150 ° C.

  The organic solvent used in the drop polymerization method is preferably a solvent that can dissolve both the monomer, the polymerization initiator and the chain transfer agent when the chain transfer agent is used in combination, and the obtained copolymer for resist. Examples of such an organic solvent include 1,4-dioxane, isopropyl alcohol, acetone, tetrahydrofuran, methyl isobutyl ketone, γ-butyrolactone, propylene glycol monomethyl ether acetate (hereinafter also referred to as “PGMEA”), and ethyl lactate. No.

  The concentration of the monomer solution dissolved in the organic solvent is not particularly limited, but is preferably in the range of 5 to 50% by mass.

  In the drop polymerization method, a solvent is previously charged in a polymerization vessel, and the polymerization vessel is heated to a predetermined polymerization temperature, and then a monomer and a polymerization initiator, and in some cases, a molecular weight modifier are dissolved in an organic solvent. The body solution is dropped into the polymerization vessel.

  Alternatively, in this drop polymerization method, a part of the monomer is charged in a polymerization vessel in advance, and the polymerization vessel is heated to a predetermined polymerization temperature to start the polymerization, and then the remaining monomers and the polymerization initiator, depending on the case, A monomer solution in which a molecular weight modifier is dissolved in an organic solvent is dropped into a polymerization vessel.

  The amount of some of the monomers to be charged in the polymerization vessel in advance is preferably in the range of 3 to 70% by mass based on the total amount of the monomers used. When the amount of the monomers to be charged into the polymerization vessel in advance is set to 3% by mass or more based on the total amount of the monomers to be used, the monomers having a low monomer consumption rate in the copolymerization reaction may be reduced in the latter stage of the polymerization. It is preferable because it does not generate much long chain structure of the monomer, and is excellent in solubility in a resist solvent, suppression of microgel formation in a resist solution, and line edge roughness. When the amount of the monomers to be charged in the polymerization vessel in advance is set to 70% by mass or less based on the total amount of the monomers to be used, the monomers having a high monomer consumption rate in the copolymerization reaction may be reduced in the initial stage of the polymerization. It is preferable because it does not generate much long chain structure of the monomer, and is excellent in solubility in a resist solvent, suppression of microgel formation in a resist solution, and line edge roughness.

  Further, in this drop polymerization method, at least two or more types of monomer solutions having different monomer composition ratios in consideration of the polymerization rate of each monomer, the monomer consumption rate and the copolymerization reactivity ratio are considered. Prepared and these can be added dropwise independently.

  Taking into account the polymerization rate, monomer consumption rate, and copolymerization reactivity ratio of each monomer, prepare at least two or more types of monomer solutions having different monomer composition ratios, and drop them independently. Then, since the consumption rate of each monomer in the copolymerization reaction can be kept constant, a long chain structure of the monomer having a high monomer consumption rate does not occur much in the early stage of the polymerization, and It is preferable because a long chain structure of the monomer having a low monomer consumption rate does not occur much in the latter stage, and the solubility in the resist solvent, the suppression of microgel formation in the resist solution, and the line edge roughness are excellent. Therefore, at least two or more types of monomer solutions having different monomer composition ratios are prepared, and generally, the monomer composition of the monomer having a low monomer consumption rate in the monomer solution to be dropped first. It is preferable to increase the ratio and make the monomer composition ratio of the monomer having a low monomer consumption rate in the monomer solution to be subsequently dropped smaller than that of the previous monomer solution.

  Independently dropping at least two or more types of monomer solutions means that immediately after the preceding monomer solution has been dropped into the polymerization vessel, the monomer composition ratio of the next stage is different from the monomer composition ratio of the previous stage. The solution may be started to be added dropwise, or after the monomer solution of the previous stage has been dropped into the polymerization vessel, the monomer solution of the next stage may be started to be dropped at an arbitrary timing until the completion of the polymerization. . In some cases, the dropping of the next-stage monomer solution may be started before the completion of the dropping of the previous-stage monomer solution.

  Resist copolymer obtained by the production method of the present invention is excellent in solubility in a resist solvent, and by using the resist copolymer of the present invention, suppression of microgel formation in a resist solution, The present inventors presume as follows about the reason for exhibiting excellent performance in line edge roughness.

  That is, since the conventional copolymer for resist has a long monomer chain length of the same kind in one molecular chain, the monomer chain distribution becomes non-uniform as a whole of the copolymer for resist, and the copolymer in the resist solvent is dissolved. The properties were not sufficient, and microgels were formed in the resist solution. Further, when the monomer chain distribution is not uniform, the distribution of the protecting groups released by acid on the surface and inside of the resist film becomes non-uniform, thereby resulting in poor line edge roughness.

  On the other hand, the copolymer for resist of the present invention has a shorter monomer chain length in one molecular chain than that of the prior art by controlling the monomer chain distribution. The present invention solves the problems of the prior art by making the monomer chain distribution uniform throughout the copolymer.

  The weight average molecular weight of the copolymer for resist of the present invention is not particularly limited, but is preferably in the range of 1,000 to 100,000.

  Next, an example of a method for using the resist copolymer of the present invention will be described.

  The copolymer solution for resist manufactured by a method such as solution polymerization is adjusted to an appropriate solution viscosity with a good solvent such as 1,4-dioxane, acetone, tetrahydrofuran, methyl isobutyl ketone, γ-butyrolactone, PGMEA, and ethyl lactate. After dilution, it is dropped into a large amount of a poor solvent such as methanol or water to precipitate a resist copolymer.

  Thereafter, the precipitate is separated by filtration and sufficiently dried.

  This step is generally called "reprecipitation" and may be unnecessary in some cases, but is very effective for removing unreacted monomers, polymerization initiator, and the like remaining in the polymerization solution. If these unreacted substances remain as they are, they may adversely affect the resist performance, so it is preferable to remove as much as possible.

  In order to obtain the resist composition of the present invention, the resist copolymer of the present invention is dissolved in a solvent. This solvent is arbitrarily selected depending on the purpose, but the selection of the solvent may be restricted by reasons other than the solubility of the resin, for example, the uniformity, appearance, safety and the like of the coating film.

  Examples of the solvent generally used in the present invention include linear ketones such as methyl ethyl ketone, 2-pentanone and 2-hexanone, cyclic ketones such as cyclopentanone and cyclohexanone, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether. Propylene glycol monoalkyl ethers such as propylene glycol monoalkyl acetates such as acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoalkyl ether acetates such as ethylene glycol monoethyl ether acetate, and propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and propylene glycol monoethyl ether , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monoalkyl ethers such as lenglycol monoisopropyl ether; diethylene glycol alkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol monomethyl ether and diethylene glycol diethyl ether; esters such as ethyl acetate and ethyl lactate; n-propyl alcohol; And alcohols such as isopropyl alcohol, n-butyl alcohol, n-butyl alcohol, tert-butyl alcohol, cyclohexanol and 1-octanol, 1,4-dioxane, ethylene carbonate and γ-butyrolactone.

  These solvents may be used alone or in combination of two or more.

  The amount of the solvent to be used is usually 200 parts by mass or more, more preferably 300 parts by mass or more, based on 100 parts by mass of the resist polymer (copolymer of the present invention). The amount of the solvent to be used is usually 5,000 parts by mass or less, more preferably 2,000 parts by mass or less, based on 100 parts by mass of the resist polymer (copolymer of the present invention).

  When the resist copolymer of the present invention is used for a chemically amplified resist, it is necessary to use a photoacid generator.

  The photoacid generator can be arbitrarily selected from those which can be used as an acid generator for a chemically amplified resist composition.

  Examples of such a photoacid generator include an onium salt compound, a sulfonimide compound, a sulfone compound, a sulfonate compound, a quinonediazide compound, and a diazomethane compound. Among them, onium salt compounds such as sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts are preferred.

  Specifically, triphenylsulfonium triflate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium naphthalene sulfonate, (hydroxyphenyl) benzylmethylsulfonium toluenesulfonate, diphenyliodonium triflate, diphenyliodonium pyrenesulfonate, diphenyliodonium dodecylbenzenesulfonate, And diphenyliodonium hexafluoroantimonate.

  The photoacid generators can be used alone or in combination of two or more.

  The amount of the photoacid generator used is conveniently selected depending on the type of the photoacid generator selected, but is usually 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the copolymer for resist. Parts by weight.

  By setting the amount of the photoacid generator used in this range, a chemical reaction by the catalytic action of the acid generated by exposure can be sufficiently generated. When the amount of the photoacid generator is 0.1 parts by mass or more, a chemical reaction due to the catalytic action of the acid generated by exposure can be sufficiently caused. When the amount is 20 parts by mass or less, the stability of the resist composition can be improved. This is preferable because it can prevent the occurrence of unevenness in application of the composition and scum during development.

  Further, the resist composition of the present invention may optionally contain various additives such as a surfactant, a quencher, a sensitizer, an antihalation agent, a storage stabilizer, and an antifoaming agent. Any of these additives can be used if they are known in the art. The amounts of these additives are not particularly limited, and may be determined as appropriate.

  Next, an example of the pattern manufacturing method of the present invention will be described.

  First, the resist composition of the present invention is applied to the surface of a substrate to be processed such as a silicon wafer on which a pattern is to be formed, by spin coating or the like. The substrate to which the chemically amplified resist composition has been applied is dried by baking (pre-bake) or the like to form a resist film on the substrate.

  Then, the resist film thus obtained is irradiated with light having a wavelength of 250 nm or less (exposure) through a photomask. The light used for the exposure is preferably KrF excimer laser light or ArF excimer laser light, and particularly preferably ArF excimer laser light.

  After light irradiation (exposure), the substrate is appropriately heat-treated (post-exposure bake, PEB), the substrate is immersed in an alkali developer, and the exposed portion is dissolved and removed in the developer (development). Any known alkaline developer may be used. After the development, the substrate is appropriately rinsed with pure water or the like. Thus, a resist pattern is formed on the substrate to be processed.

  Usually, the substrate on which a resist pattern has been formed is appropriately heat-treated (post-baked) to strengthen the resist and selectively etch portions where there is no resist. After etching, the resist is usually removed using a stripping agent.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples. In the Examples and Comparative Examples, “parts” means “parts by weight” unless otherwise specified. The measurement of physical properties and the like in Examples and Comparative Examples was performed using the following methods.

(1) Weight average molecular weight of resist polymer A resist solution of about 20 mg was dissolved in 5 mL of tetrahydrofuran, and a sample solution filtered through a 0.5 μm membrane filter was subjected to gel permeation chromatography (GPC) manufactured by Tosoh Corporation. It measured using. The separation column is a series of three Shodex GPC K-805L (trade name), the solvent is tetrahydrofuran, the flow rate is 1.0 mL / min, the detector is a differential refractometer, the measurement temperature is 40 ° C., the injection amount is 0.1 mL, and the standard polymer is polystyrene. It was used.

(2) Average copolymer composition ratio (mol%) of resist copolymer
^It was determined by ¹ H-NMR measurement. This measurement was performed using GSX-400 type FT-NMR (trade name) manufactured by JEOL Ltd., using about 5% by mass of a resist copolymer sample as deuterated chloroform, deuterated acetone, or deuterated acetone. Dimethyl sulfoxide was put into a test tube having a diameter of 5 mmφ, and the measurement was performed 64 times in a single pulse mode at a measurement temperature of 40 ° C. and an observation frequency of 400 MHz.

(3) Solubility in resist solvent The resist copolymer was stirred with a predetermined amount of PGMEA and ethyl lactate (hereinafter also referred to as “EL”) at room temperature so that the solid content concentration was 20% by mass. After dissolution, the time until complete dissolution was measured.

The meaning of the symbols in Table 1 is that the time until the resist copolymer is completely dissolved is
◎: less than 1 hour,
： １: 1 hour or more and less than 3 hours
Δ: 3 hours or more and less than 24 hours
×: 24 hours or more, or insoluble
It is.

(4) Sensitivity After 100 parts of the copolymer for resist was mixed with 2 parts of triphenylsulfonium triflate as a photoacid generator and 700 parts of PGMEA as a solvent to form a uniform solution, the membrane filter having a pore size of 0.1 μm. And filtered to prepare a resist composition solution. Thereafter, this composition solution was spin-coated on a silicon wafer, and prebaked at 120 ° C. for 60 seconds using a hot plate to form a resist film having a thickness of 0.4 μm. Next, after exposure using an ArF excimer laser exposure machine, baking was performed after exposure at 120 ° C. for 60 seconds using a hot plate. Next, the resist film was developed with a 2.38% by mass aqueous solution of tetramethylammonium hydroxide at room temperature, washed with pure water, and dried to form a resist pattern.

(5) Sensitivity The exposure amount (mJ / cm ² ) at which a 0.16 μm line-and-space pattern mask was transferred to a 0.16 μm line width was measured as the sensitivity.

(6) Resolution The minimum dimension (μm) of the resist pattern resolved when the above exposure amount was exposed was defined as the resolution.

(7) Amount of microgel The resist composition solution prepared as described above was treated with micro solution in the solution immediately after preparation (initial value of microgel) and after standing at 4 ° C. for 1 week (number of microgel after aging). The number of gels was counted with a Rion particle counter. Along with the initial microgel value, the number of microgel increases calculated by (number of microgels after aging)-(initial microgel value) was evaluated. The number of microgels having a particle size of 0.25 μm or more in 1 ml of the resist composition solution was counted.

(8) Line edge roughness In the range of 5 μm in the longitudinal direction of the 0.20 μm resist pattern obtained by the minimum exposure amount that reproduces the 0.20 μm resist pattern in the mask, the pattern side edge should be from the reference line where the pattern side edge should be. Was measured at 50 points with a JEOL JSM-6340F type field emission scanning electron microscope, the standard deviation was determined, and 3σ was calculated. A smaller value indicates better performance.

(9) Uprightness of the resist pattern The vertical direction of the resist pattern of 0.20 μm was observed with a JSM-6340F type field emission scanning electron microscope (trade name) manufactured by JEOL. The number of patterns with distortion or collapse was examined. A smaller value indicates better performance.

(10) Roughness of resist film surface after dry etching treatment A silicon wafer coated with a 0.4 μm-thick resist film (formed using the above-prepared resist composition solution) is applied to a Showa Vacuum SPE-220T dry type silicon wafer. Dry etching was performed with an etching device (trade name). The processing conditions were as follows: gas type and gas flow rate (standard state): CF ₄ / O ₂ = 95 cm ³ /min/5.0 cm ³ / min; processing chamber pressure: 15 Pa; plasma power: 200 W; did. Then, for a measurement range of 1 μm × 1 μm, the distance from the reference line where the resist film surface should be located was determined by using an SPI3700 / SPA-300 type atomic force microscope (trade name) manufactured by Seiko Instruments equipped with a silicon nitride cantilever. 100 points were measured, the standard deviation was determined, and 3σ was calculated. A smaller value indicates better performance. The measurement was performed in the AFM mode with the number of scanning lines being 256.

<Example 1>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, under a nitrogen atmosphere, 29.1 parts of PGMEA and 3.2 parts of γ-butyrolactone were added. Raised. 19.3 parts of 2-exo-methacryloyloxy-4,8-dioxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one (sometimes referred to as ONLMA), 4-methacryloyloxy- 4-ethyl - tetracyclo [6.2.1.1 ^3,6 .0 ^2,7] (sometimes expressed as EDMA) dodecane 20.8 parts, be expressed as 1-acryloyloxy-3-hydroxyadamantane (HAdA 8.4 parts, 101.9 parts of PGMEA, 11.3 parts of γ-butyrolactone, 0.58 part of 1-octanethiol, 0.50 part of 2,2′-azobisisobutyronitrile The solution was dropped into the flask at a constant speed over a period of 6 hours from the dropping device containing the body solution, and then the temperature at 80 ° C. was maintained for 1 hour. Next, the obtained reaction solution was added dropwise with stirring to about 30 times the amount of methanol with respect to the monomer used for the polymerization to obtain a white precipitate (copolymer A-1). In order to completely remove the monomer remaining in the precipitate, the resulting precipitate was separated by filtration and washed in about 30 times the amount of methanol with respect to the monomer used for the polymerization. The obtained precipitate was separated by filtration and dried at 50 ° C. under reduced pressure for about 40 hours. Table 1 shows the results of measuring the properties of the obtained copolymer A-1.

<Example 2>
Under a nitrogen atmosphere, 37.1 parts of tetrahydrofuran was charged into a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and the temperature of the hot water bath was raised to 70 ° C. while stirring. 18.3 parts of 2-exo-acryloyloxy-4-oxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one (may be referred to as OTNA), 2-methacryloyloxy-2-methyl From a dropping device containing a monomer solution obtained by mixing 26.2 parts of adamantane (may be expressed as MAdMA), 66.8 parts of tetrahydrofuran, and 4.60 parts of dimethyl-2,2'-azobisisobutyrate, The solution was dropped into the flask over a period of 6 hours at a constant speed, and then the temperature of 70 ° C. was maintained for 1 hour. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-2. Table 1 shows the results of measuring the properties of the obtained copolymer A-2.

<Example 3>
Under a nitrogen atmosphere, 53.4 parts of PGMEA, 8- or 9-methacryloyloxy-4-oxatricyclo [5.2.1.0] were added to a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer. ^2,6 ] decane-3-one (sometimes referred to as OTDMA) 2.0 parts, 8- or 9-acryloyloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decane-3 5.2 parts of -one (may be expressed as OTDA), 3.3 parts of 2-methacryloyloxy-2-ethyladamantane (may be expressed as EAdMA), and 3.3 parts of HAdA are added (monomer composition ratio: (OTDMA / OTDA / EAdMA / HAdA = 14/39/22/25 (mol%)), and the temperature of the hot water bath was raised to 80 ° C. with stirring. Thereafter, an initiator / chain transfer agent solution obtained by mixing 5.9 parts of γ-butyrolactone, 0.06 parts of 2-mercaptoethanol, and 0.30 parts of 2,2′-azobisisobutyronitrile was charged into the flask, The polymerization was started. Immediately after that, 5.9 parts of OTDMA, 11.0 parts of OTDA, 10.8 parts of EAdMA, and 4.8 parts of HAdA (monomer composition ratio: OTDMA / OTDA / EAdMA / HAdA = 18 / 35.5 / 31 / 15.5 ( mol%)), 44.0 parts of PGMEA, 4.9 parts of γ-butyrolactone, 0.14 part of 2-mercaptoethanol, and 0.68 part of 2,2′-azobisisobutyronitrile. The mixture was dropped into the flask over a period of 6 hours at a constant speed from the dropping device, and then kept at 80 ° C. for 30 minutes. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-3. Table 1 shows the results of measuring the properties of the obtained copolymer A-3.

<Example 4>
Under a nitrogen atmosphere, 38.4 parts of PGMEA was charged into a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 6.5 parts of OTDA, 4.3 parts of EAdMA, 2.9 parts of HAdA (monomer composition ratio: OTDA / EAdMA / HAdA = 49/29/22 (mol%)), 20.7 parts of PGMEA, 0.08 of 1-octanethiol , 2,2'-azobisisobutyronitrile was dropped into the flask at a constant rate over a period of 1.5 hours from a dropping device containing a monomer solution in which 0.34 part of 2,2'-azobisisobutyronitrile was mixed. Immediately after dropping the dropping solution, 14.0 parts of OTDA, 12.2 parts of EAdMA, 6.2 parts of HAdMA (monomer composition ratio: OTDA / EAdMA / HAdA = 45/35/20 (mol%)), PGMEA 48 0.5 part, 0.20 part of 1-octanethiol, and 0.80 part of 2,2'-azobisisobutyronitrile from a dropping device containing a monomer solution mixed over 4.5 hours at a constant speed. It was dropped into the flask. Thereafter, the temperature of 80 ° C. was maintained for 30 minutes. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-4. Table 1 shows the results of measuring the properties of the obtained copolymer A-4.

<Example 5>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, under a nitrogen atmosphere, 31.0 parts of PGMEA and 13.3 parts of γ-butyrolactone were added. Raised. 22.8 parts of a mixture of a monomer represented by the following formula (20-1) and a monomer represented by the following formula (20-2) (hereinafter, referred to as DOLAMA);

19.2 parts of MAdMA, 11.1 parts of HAdA, 55.8 parts of PGMEA, 23.9 parts of γ-butyrolactone, 0.14 parts of 1-octanethiol, and 1.32 parts of 2,2′-azobisisobutyronitrile were mixed. From the dropping device containing the monomer solution, the solution was dropped into the flask at a constant speed over 6 hours, and then the temperature at 80 ° C. was maintained for 1 hour. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-5. Table 1 shows the results of measuring the properties of the obtained copolymer A-5.

<Example 6>
Under a nitrogen atmosphere, 34.7 parts of PGMEA was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 7. 7.8 parts of OTDA, 15.7 parts of 1-methacryloyloxy-1-ethylcyclohexane (hereinafter referred to as ECHMA), 2- or 3-cyano-5-norbornyl methacrylate (hereinafter referred to as CNNMA). 2 parts, 62.5 parts of PGMEA, 0.12 parts of 1-octanethiol, and 1.32 parts of 2,2′-azobisisobutyronitrile were dropped at a constant speed from a dropping device containing a monomer solution. The mixture was dropped into the flask over a period of time, and then the temperature of 80 ° C. was maintained for 1 hour. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-6. Table 1 shows the results of measuring the properties of the obtained copolymer A-6.

<Example 7>
Under a nitrogen atmosphere, 37.2 parts of PGMEA was put into a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 17.2 parts of a mixture of a monomer represented by the following formula (21-1) and a monomer represented by the following formula (21-2) (hereinafter referred to as DOLA);

A drop containing a monomer solution obtained by mixing 18.7 parts of MAdMA, 12.9 parts of HAdA, 73.2 parts of PGMEA, 0.24 parts of 1-octanethiol, and 1.32 parts of 2,2′-azobisisobutyronitrile. The solution was dropped into the flask at a constant speed over a period of 6 hours, and then the temperature of 80 ° C. was maintained for 1 hour. The subsequent operations were the same as those in Example 1 to obtain a copolymer A-7. Table 1 shows the results of measuring the properties of the obtained copolymer A-7.

<Comparative Example 1>
Under a nitrogen atmosphere, 38.9 parts of tetrahydrofuran was charged into a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and the temperature of the water bath was raised to 70 ° C. while stirring. 25.3 parts of 2-exo- (meth) acryloyloxy-4-oxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one (may be referred to as OTNMA), 21.3 parts of EAdMA, From a dropping device containing a monomer solution obtained by mixing 70.0 parts of tetrahydrofuran and 4.60 parts of dimethyl-2,2'-azobisisobutyrate, the solution was dropped into the flask at a constant speed over a period of 6 hours. , 70 ° C for 1 hour. The subsequent operations were the same as those in Example 1 to obtain a copolymer B-1. Table 1 shows the results of measuring the properties of the obtained copolymer B-1.

<Comparative Example 2>
Under a nitrogen atmosphere, 27.0 parts of OTNA, 17.4 parts of EAdMA, 73.2 parts of PGMEA, and 0.30 part of 1-octanethiol were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer while stirring. The temperature of the water bath was raised to 70 ° C. An initiator solution obtained by mixing 20.0 parts of PGMEA, 5.2 parts of γ-butyrolactone, and 1.96 parts of 2,2′-azobisisobutyronitrile was charged into a flask to initiate polymerization. Thereafter, the temperature of 70 ° C. was maintained for 7 hours. The subsequent operations were the same as those in Example 1 to obtain a copolymer B-2. Table 1 shows the results of measuring the properties of the obtained copolymer B-2.

<Comparative Example 3>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, 38.1 parts of PGMEA and 11.9 parts of γ-butyrolactone were added under a nitrogen atmosphere, and the temperature of the hot water bath was adjusted to 80 ° C while stirring. Raised. OTDA 17.3 parts, 2-acryloyloxy-2-methyladamantane (may be expressed as MAdA) 24.6 parts, HAdA 8.9 parts, PGMEA 68.6 parts, γ-butyrolactone 7.6 parts, 2-mercaptoethanol 0.16 parts, 2,2'-azobisisobutyronitrile 1.14 parts of a monomer solution containing a mixture was dropped into the flask over a period of 6 hours at a constant rate from the dropping device, then 80 C. was maintained for 1 hour. Subsequent operations were performed in the same manner as in Example 1, except that the obtained reaction solution was added dropwise to a mixed solution of water / methanol (20/80 (vol%)) in an amount of about 30 times while stirring. Polymer B-3 was obtained. Table 1 shows the results of measuring the properties of the obtained copolymer B-3.

<Comparative Example 4>
Under a nitrogen atmosphere, 5.0 parts of OTNA, 13.8 parts of OTNMA, 26.7 parts of MAdMA, and 76.0 parts of tetrahydrofuran were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and stirred with a water bath. Was raised to 70 ° C. An initiator solution obtained by mixing 30.0 parts of tetrahydrofuran and 5.52 parts of dimethyl-2,2'-azobisisobutyrate was charged into the flask, and polymerization was started. Thereafter, the temperature of 70 ° C. was maintained for 7 hours. The subsequent operations were the same as those in Example 1 to obtain a copolymer B-4. Table 1 shows the results of measuring the properties of the obtained copolymer B-4.

As described above, in Examples 1 to 7, the sensitivity and / or resolution were not impaired, the solubility in the resist solvent, the uprightness of the resist pattern by heat treatment, the line edge roughness were improved, and the resist film surface after the dry etching treatment was performed. Roughness was reduced and microgel formation in the resist solution was suppressed. On the other hand, in Comparative Examples 1 and 4, although the uprightness of the resist pattern was improved by the heat treatment, the solubility in the resist solvent and the line edge roughness were not improved, and generation of microgels in the resist solution was confirmed. Also, the surface roughness of the resist film after the dry etching was not sufficiently improved. In Comparative Examples 2 and 3, the solubility in the resist solvent, the line edge roughness, the surface roughness of the resist film after the dry etching treatment were improved, and the formation of microgels in the resist solution was suppressed. The uprightness of the resist pattern was not sufficiently improved.

Claims (13)

A resist copolymer containing a monomer unit having an alicyclic skeleton, wherein the resist copolymer contains an acrylic monomer unit in an amount of 20 mol% to 68 mol%. For copolymers. The resist copolymer according to claim 1, wherein the monomer unit having an alicyclic skeleton is at least one monomer unit selected from the following formulas (A1) to (A4) and (A10).

(In the formulas (A1) to (A4) and (A10), R represents a hydrogen atom or a methyl group, and R ¹ , R ² , and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms. ⁴ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ^{41 to} R ⁴⁴ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or a carbon atom. R ^{45 to} R ⁴⁸ each independently represent a hydrogen atom, —R ⁵⁰ —CN, —R ⁵¹ —CH (CN) ₂ , —R ⁵² —COO. —R ⁵³ , — (CH ₃ ) _m —C (CF ₃ ) ₂ —OH, wherein R ⁴⁹ is a hydrogen atom, an alkoxy group having 1 to 3 carbon atoms which may have a branch, a cyano group Or an ester group having 1 to 6 carbon atoms, and R ^{50 to} R ⁵² each independently represent a carbon atom. X represents an alkylene group which may have a branch or a single bond, and R ⁵³ represents an acid-eliminable group, and X and Y each independently represent -O- or -CH _2-. , —CH ₂ CH ₂ —, m represents an integer of 0 to 6, p represents an integer of 0 to 2. R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or a hydroxyl group. R ¹⁰¹ represents an alkyl group having 1 to 3 carbon atoms, and r represents an integer of 0 to 2.) 3. The copolymer for resist according to claim 1, wherein the copolymer for resist contains a monomer unit having a lactone skeleton. A resist copolymer containing a monomer unit having a lactone skeleton, wherein the resist copolymer contains an acrylic monomer unit in an amount of 20 mol% or more and 68 mol% or less. Polymer. 5. The resist copolymer according to claim 3, wherein the monomer unit having a lactone skeleton is at least one monomer unit selected from the following formulas (A5) and (A6).

(In the formula (A5), R represents a hydrogen atom or a methyl group, and R ⁶¹ and R ⁶² each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group, or a carbon number. A ¹ and A ² each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or 1 to 6 carbon atoms; 6 represents a carboxy group esterified with an alcohol, or A ¹ and A ² together represent —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— ( CH ₂ ) _q — (q represents an integer of 1 to 6)], wherein X ⁵ is a hydroxyl group, a carboxy group, an acyl group having 1 to 6 carbon atoms, or an alcohol having 1 to 6 carbon atoms as a substituent. Esterified carboxy group, shea A linear or branched alkyl group having 1 to 6 carbon atoms, which may have at least one group selected from the group consisting of a group and an amino group, a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, carbon Represents an alkoxy group having 1 to 6 carbon atoms, a carboxy group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group or an amino group, and n5 represents an integer of 0 to 4. In the case where n5 is 2 or more, Also includes having a plurality of different groups as X ⁵ .
In the formula (A6), R represents a hydrogen atom or a methyl group, and R ⁶³ and R ⁶⁴ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or a 1 carbon atom. represents esterified carboxy group at 6 alcohol, a ^3, a ⁴ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, hydroxy group, the number carboxy group or a carbon 1-6 Represents a carboxy group esterified with an alcohol of the formula (I), or A ³ and A ⁴ are taken together to form —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— (CH ₂ ) _r- (r represents an integer of 1 to 6)]. X ⁶ is at least one selected from the group consisting of a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, a carboxy group esterified with an alcohol having 1 to 6 carbon atoms, a cyano group and an amino group. A linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol, and n6 represents an integer of 0 to 4. Incidentally, also includes having a plurality of different groups as X ⁶ in the case of n6 is 2 or more. ) The total content of the monomer unit having an alicyclic skeleton and the monomer unit having a lactone skeleton is at least 80 mol% of all monomer units constituting the copolymer for resist. The copolymer for resist according to any one of the above. The method for producing a resist copolymer according to any one of claims 1 to 6, wherein a solvent is previously charged into a polymerization vessel, and the polymerization vessel is heated to a predetermined polymerization temperature, and then polymerized with a monomer. A method for producing a copolymer for resists, comprising dropping a monomer solution in which an initiator is dissolved in an organic solvent into a polymerization vessel. The method for producing a resist copolymer according to any one of claims 1 to 6, wherein a part of the monomers is charged into a polymerization vessel in advance, and the polymerization vessel is heated to a predetermined polymerization temperature to carry out the polymerization. A method for producing a copolymer for resists, comprising, after starting the above, a monomer solution obtained by dissolving the remaining monomers and a polymerization initiator in an organic solvent is dropped into a polymerization vessel. The method for producing a resist copolymer according to claim 7 or 8, wherein at least two or more monomer solutions having different monomer composition ratios are independently dropped into a polymerization vessel. Of producing a copolymer for resist. A resist composition comprising the copolymer for a resist according to claim 1. A pattern manufacturing method comprising at least a step of applying the resist composition according to claim 10 on a substrate to be processed, and a step of exposing the resist composition to light having a wavelength of 250 nm or less. 12. The pattern manufacturing method according to claim 11, wherein the light used for exposure is ArF excimer laser light. A pattern manufacturing method comprising at least a step of applying the resist composition according to claim 10 on a substrate to be processed and a step of exposing the substrate to an electron beam.