JP5062943B2 - Copolymer for resist and method for producing the same, resist composition, and pattern forming method - Google Patents

Description

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

  In recent years, in the field of microfabrication in the manufacture of semiconductor elements and liquid crystal elements, miniaturization has rapidly progressed due to advances in lithography technology. As a technique for miniaturization, generally, the wavelength of irradiation light emitted from an exposure light source is shortened. Specifically, the conventional ultraviolet ray typified by g-line and i-line has changed to DUV (Deep Ultra Violet). ing.

At present, KrF excimer laser (248 nm) lithography technology has been introduced to the market, ArF excimer laser (193 nm) lithography technology has been introduced to further shorten the wavelength, and the next generation technology is F ₂ excimer laser. Lithography technology is being studied (157 nm). In addition, as a slightly different type of lithography technique, electron beam lithography technique has been energetically studied.

  As a high-resolution resist for such short-wavelength irradiation light or electron beam, a “chemically amplified resist” containing a photoacid generator has been proposed. At present, improvements and development of this chemically amplified resist are energetically active. It is being advanced.

  Also, the structure of the resin used for the resist has changed in response to the shortening of the wavelength of the irradiation light. In KrF excimer laser lithography, polyhydroxystyrene or a hydroxyl group thereof protected with an acid dissociable, dissolution inhibiting group was used. However, in ArF excimer laser lithography, the resin is transparent when irradiated with a wavelength of 193 nm. Is insufficient and almost unusable, and transparent acrylic resins are attracting attention at this wavelength. Examples of such acrylic resins include copolymers of (meth) acrylic acid ester having an adamantane skeleton in the ester portion and (meth) acrylic acid ester having a lactone skeleton in the ester portion. Etc. are described.

  In a method for producing a resist copolymer containing a structural unit having such a lactone skeleton, a method using a lactone as a polymerization solvent is described in Patent Document 3 and the like.

However, when such a copolymer is used as a resist composition, the copolymer in the resist solution once uniformly dissolved aggregates with time, and an insoluble matter called microgel is generated, resulting in a resist pattern. Occurrence of defects may cause problems such as circuit disconnection or defects, which may reduce the yield in the semiconductor manufacturing process. Further, resist pattern side wall roughness (hereinafter also referred to as “line edge roughness”) generated by patterning with an excimer laser and subsequent development processing occurs, causing problems such as non-uniform circuit width, circuit disconnection, and defects. This may cause a decrease in the yield in the semiconductor manufacturing process as in the case of the microgel.

  As described above, there is a demand for an excellent resist copolymer in which microgel formation in a resist solution is suppressed and line edge roughness is small without impairing the high sensitivity and resolution of a resist industrially. Currently.

JP 10-319595 A JP-A-10-274852 Japanese Patent Laid-Open No. 2002-6502

  The present invention has been made to solve the above-described problems of the prior arts, and the object of the present invention is to provide a resist with high sensitivity and resolution when used in DUV excimer laser lithography or electron beam lithography. An object of the present invention is to provide a resist copolymer and a method for producing the same, in which the formation of microgel in the resist solution is suppressed and the line edge roughness is low without being impaired.

  The present inventors have intensively studied to achieve the above object, and in particular, paying attention to the relationship between the polymerization solvent in producing the resist copolymer and the consumption rate of each monomer, and as a result, polymerization By controlling the consumption rate of the monomer having a lactone skeleton by the solvent, the formation of microgel in the resist solution using the obtained resist copolymer is suppressed, and further, the resist obtained using the resist It has been found that the line edge roughness of the pattern is greatly reduced, and the present invention has been completed.

That is, the first gist of the present invention is to use a monomer containing a monomer having a lactone skeleton and a polymerization solvent containing a lactone, and determine the abundance ratio of the lactone in the polymerization solvent. It is a manufacturing method of the copolymer for resists characterized by reducing with progress of this.

  The second gist of the present invention is the above method for producing a resist copolymer, wherein the monomer having a lactone skeleton is at least one selected from the following formulas (1) to (7).

(In the formula (1), R ⁴¹ represents a hydrogen atom or a methyl group, and R ⁴⁰¹ and R ⁴⁰² 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. Represents a carboxy group esterified with an alcohol having 1 to 6 or R ⁴⁰¹ and R ⁴⁰² together form —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms; [— (CH ₂ ) _j — (j represents an integer of 1 to 6)], i represents 0 or 1, and X ⁵ represents a hydroxy group, a carboxy group, or a carbon number of 1 to 6 as a substituent. Carbon which may have at least one group selected from the group consisting of an acyl group, 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 and an amino group A linear or branched alkyl group of 1 to 6 A hydroxy group, a carboxy group, an acyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a carboxy group or an amino group esterified with an alcohol having 1 to 6 carbon atoms, and n5 is 0 to 4 Represents an integer, and m represents 1 or 2. In addition, when n5 is 2 or more, X ⁵ includes a plurality of different groups.
Wherein (2), R ⁴² represents a hydrogen atom or a methyl group, R ^201, R ²⁰² are each independently a hydrogen atom, a linear or branched alkyl group, a hydroxy group, a carboxy group or a carbon number of 1 to 6 carbon atoms Represents a carboxy group esterified with an alcohol having 1 to 6; 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 1 carbon atoms; Represents a carboxy group esterified with an alcohol of 6, or A ¹ and A ² together represent —O—, —S—, —NH—, or a methylene chain having 1 to 6 carbon atoms [— ( CH ₂ ) _k — (k 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 as a substituent. C1-C6 linear or branched alkyl group which may have one group, a hydroxy group, a carboxy group, a C1-C6 acyl group, a C1-C6 alkoxy group, C1-C1 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. In addition, when n6 is 2 or more, it includes having a plurality of different groups as X ⁶ .
In formula (3), R ⁴³ represents a hydrogen atom or a methyl group, and R ²⁰³ and R ²⁰⁴ 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. Represents a carboxy group esterified with 1 to 6 alcohols, and A ³ and A ⁴ 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 1 carbon atoms. A carboxy group esterified with 6 alcohols, or A ³ and A ⁴ together with —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— ( CH _{2) l} - represents a (l is an integer of 1-6)]. X ⁷ 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 as a substituent. C1-C6 linear or branched alkyl group which may have one group, a hydroxy group, a carboxy group, a C1-C6 acyl group, a C1-C6 alkoxy group, C1-C1 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol of 6, and n7 represents an integer of 0 to 4. In addition, when n7 is 2 or more, it includes having a plurality of different groups as X ⁷ .
In the formula (4), R ⁴⁴ represents a hydrogen atom or a methyl group, and R ⁵¹ , R ⁶¹ and R ⁷¹ each independently represent a hydrogen atom or a methyl group. Y ¹¹ , Y ²¹ and Y ³¹ each independently represent —CH ₂ — or —CO—O—, and at least one of them represents —CO—O—. X ⁸ 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 as a substituent. C1-C6 linear or branched alkyl group which may have one group, a hydroxy group, a carboxy group, a C1-C6 acyl group, a C1-C6 alkoxy group, C1-C1 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol of 6, and n8 represents an integer of 0 to 4. Incidentally, also includes having a plurality of different groups as X ⁸ in the case of n8 is 2 or more.
In the formula (5), R ⁴⁵ represents a hydrogen atom or a methyl group, R ⁸ and R ⁹ each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, R ⁵² , R ⁶² , R ⁷² each independently represents a hydrogen atom or a methyl group. Y ¹² , Y ²² and Y ³² each independently represent —CH ₂ — or —CO—O—, and at least one of them represents —CO—O—. X ⁹ 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 as a substituent. C1-C6 linear or branched alkyl group which may have one group, a hydroxy group, a carboxy group, a C1-C6 acyl group, a C1-C6 alkoxy group, C1-C1 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol of 6, and n9 represents an integer of 0 to 4. In addition, when n9 is 2 or more, it includes having a plurality of different groups as X ⁹ .
In the formula (6), R ⁴⁶ represents a hydrogen atom or a methyl group, R ¹⁰ represents a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, and R ⁵³ , R ⁶³ and R ⁷³ are each independently Represents a hydrogen atom or a methyl group. Y ¹³ , Y ²³ and Y ³³ each independently represent —CH ₂ — or —CO—O—, and at least one of them represents —CO—O—. X ¹⁰ represents 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 as a substituent. C1-C6 linear or branched alkyl group which may have one group, a hydroxy group, a carboxy group, a C1-C6 acyl group, a C1-C6 alkoxy group, C1-C1 6 represents a carboxy group, a cyano group or an amino group esterified with an alcohol of 6, and n10 represents an integer of 0 to 4. Incidentally, also includes having a plurality of different groups as X ¹⁰ in the case of n10 is 2 or more.
In formula (10), R ⁹¹ , R ⁹² , R ⁹³ and R ⁹⁴ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a hydroxy group, a carboxy group or an alcohol having 1 to 6 carbon atoms. Or R ⁹¹ and R ⁹² together represent —O—, —S—, —NH— or a C 1-6 methylene chain [— (CH ₂ ) _t- (t represents an integer of 1 to 6)], and m1 represents 1 or 2. )

  In the above method for producing a copolymer for resist, it is desirable to include a monomer having an acid leaving group. Here, the “acid leaving group” means a group that decomposes or leaves by the action of an acid.

  The monomer having an acid leaving group is preferably at least one monomer selected from the following formulas (8) to (11).

(In Formula (8), R ³¹ represents a hydrogen atom or a methyl group, R ¹ represents an alkyl group having 1 to 3 carbon atoms, and X ¹ represents a hydroxy group, a cyano group, a carboxy group, or a carbon number as a substituent. A straight chain having 1 to 6 carbon atoms which may have at least one group selected from the group consisting of an acyl group having 1 to 6 carbon atoms, an ester group with a carboxy group esterified with an alcohol having 1 to 6 carbon atoms, and an amino group; Represents a branched alkyl group, a hydroxy group, a cyano group, a carboxy group, an acyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a carboxy group or an amino group esterified with an alcohol having 1 to 6 carbon atoms. , N1 represents an integer of 0 to 4. In addition, when n1 is 2 or more, it includes that X ¹ has a plurality of different groups.
In the formula (9), R ³² represents a hydrogen atom or a methyl group, and R ² and R ³ each independently represents an alkyl group having 1 to 3 carbon atoms which may be substituted with a hydroxy group, a cyano group or an amino group. And X ² is selected from the group consisting of a hydroxy group, a cyano 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, and an amino group as a substituent. A linear or branched alkyl group having 1 to 6 carbon atoms, which may have at least one group, a hydroxy group, a cyano group, a carboxy group, an acyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms Represents a carboxy group or an amino group esterified with an alcohol having 1 to 6 carbon atoms, and n2 represents an integer of 0 to 4. Incidentally, also includes having a plurality of different groups as X ² in the case of n2 is 2 or more.
In Formula (10), R ³³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 1 to 3 carbon atoms, and R ³³¹ , R ³³² , R ³³³ , and R ³³⁴ are each independently a hydrogen atom, carbon Represents a linear or branched alkyl group having 1 to 6 and Z ¹ and Z ² are each independently —O—, —S—, —NH— or a methylene chain having 1 to 6 carbon atoms [— (CH ₂ ) _u1 -(U1 represents an integer of 1 to 6)], and X ³ is an ester with a hydroxy group, a cyano 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. A straight-chain or branched alkyl group having 1 to 6 carbon atoms, which may have at least one group selected from the group consisting of a carboxy group and an amino group, a hydroxy group, a cyano group, a carboxy group, and a carbon number of 1 ˜6 acyl group, C 1-6 alkoxy group, carbon number Represents esterified carboxyl group or an amino group at 6 alcohol, n3 represents an integer of 0 to 4, q is 0 or 1. In addition, when n3 is 2 or more, it includes having a plurality of different groups as X ³ .
In formula (11), R ³⁴ represents a hydrogen atom or a methyl group, R ⁵ represents an alkyl group having 1 to 3 carbon atoms, X ⁴ represents a hydroxy group, a cyano group, a carboxy group, or a carbon number 1 as a substituent. A straight chain or branched chain having 1 to 6 carbon atoms, which may have at least one group selected from the group consisting of an acyl group of -6, a carboxy group esterified with an alcohol having 1 to 6 carbons, and an amino group An alkyl group, a hydroxy group, a cyano group, a carboxy group, an acyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a carboxy group or an amino group esterified with an alcohol having 1 to 6 carbon atoms, n4 represents an integer of 0 to 4, and r represents an integer of 0 to 2. In addition, when n4 is 2 or more, it includes having a plurality of different groups as X ⁴ . )

  The third gist of the present invention is the polymer as described above, wherein the polymerization is carried out while a solution obtained by dissolving the monomer that is a constituent unit of the polymer of the present invention in an organic solvent is dropped into a polymerization vessel. It is a manufacturing method.

  The fourth gist of the present invention is a resist composition comprising a resist copolymer obtained by each of the above production methods.

  The fifth gist of the present invention is a resist polymer having a structural unit having a lactone skeleton, wherein the average copolymer composition ratio of the structural unit having a lactone skeleton in the resist copolymer is X mol%. When the copolymer composition ratio of the structural unit having a lactone skeleton in the copolymer composition distribution curve obtained by the critical adsorption chromatography method is an area ratio in the range of (X-5) mol% to (X + 5) mol%. It is a polymer for resist which is 42 to 95%.

The sixth gist of the present invention is a resist polymer having a structural unit having a lactone skeleton, wherein the average copolymer composition ratio of the structural unit having a lactone skeleton of the resist copolymer is X mol%. The copolymer composition ratio of the structural unit having a lactone skeleton in the copolymer composition distribution curve obtained by the critical adsorption chromatography method is an area ratio in the range of (X-5) mol% to (X + 5) mol%. It is -95% or more, It is a copolymer for resists manufactured with the manufacturing method of Claim 1.
The seventh gist of the present invention is a chemically amplified resist composition comprising the resist copolymer and a photoacid generator.
An eighth aspect of the present invention is a pattern comprising a step of applying the resist composition on a substrate to be processed, a step of exposing with light having a wavelength of 250 nm or less, and a step of developing using a developer. It is a forming method. The ninth gist of the present invention is a pattern forming method including a step of applying the resist composition on a substrate to be processed, a step of exposing with an electron beam, and a step of developing using a developer. It is.

  Resist copolymer resist composition obtained by the production method of the present invention, and the resist copolymer of the present invention, the formation of microgel in the resist solution is suppressed without impairing high sensitivity and resolution, In addition, the line edge roughness is small, and a highly accurate fine resist pattern can be stably formed. Therefore, the resist copolymer and 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.

The resist copolymer of the present invention contains a monomer unit having a lactone skeleton.
A monomer having a lactone skeleton has a structure having a cyclic saturated hydrocarbon containing an endocyclic carboxyl group (—CO—O—), and a monomer having an ethylenic double bond as a polymerizable functional group Is the body. By using such a monomer for the copolymerization reaction, a copolymer containing a structural unit having a lactone skeleton can be obtained.

Examples of the monomer having a lactone skeleton include (meth) acrylate having a δ-valerolactone ring, (meth) acrylate having a γ-butyrolactone ring, (meth) acrylate having a polycyclic lactone, and the like. And derivatives having a substituent on the lactone ring of the compound. More specifically, monomers represented by the above formulas (1) to (7) may be mentioned as preferable ones. In addition, 2- (1- (meth) acryloyloxy) ethyl-4-butanolide And pantoyl lactone (meth) acrylate. In the present invention, “(meth) acrylate” is a general term for acrylate and methacrylate.

  Resist copolymers consisting of structural units having a lactone skeleton have excellent adhesion to highly polar surfaces such as metal surfaces, and these structural units are protected by acid (protective groups). When it contains, it has excellent sensitivity. Furthermore, when these structural units having a lactone skeleton contain a high carbon density, they have excellent dry etching resistance.

  In order to introduce a structural unit having a lactone skeleton into the polymer, for example, a monomer having a lactone skeleton may be polymerized.

  Monomers having a lactone skeleton can be used alone or in combination of two or more as required.

  The ratio of the structural unit having a lactone skeleton is preferably in the range of 10 to 90 mol%, more preferably in terms of the number of microgels of the resist composition, sensitivity, resolution, and adhesion to the substrate, relative to the whole polymer. Is in the range of 30 to 70 mol%.

  The monomer having a lactone skeleton is preferably a compound represented by the above formulas (1) to (7) from the viewpoint of high resist sensitivity and resolution.

  As specific examples of the formula (1), the following formulas (1-1) to (1-4)

Is mentioned. Among these, monomers represented by (1-1) and (1-4) are preferable from the viewpoint of sensitivity and resolution. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (2), the following formulas (2-1) to (2-4)

Is mentioned. Among these, from the viewpoint of dry etching resistance, the monomers represented by the above formulas (2-2) and (2-4) are preferable. From the viewpoint of solubility in a resist solvent, the above formula (2-3) The monomer represented is preferred. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (3), the following formulas (3-1) to (3-8)

Is mentioned. Among these, from the viewpoint of dry etching resistance, the monomers represented by the above formulas (3-2), (3-4), (3-6) and (3-8) and their geometric isomers, optical isomerism The monomers represented by the above formulas (3-3) and (3-7) and their geometrical isomers and optical isomers are preferable from the viewpoint of solubility in a resist solvent. R represents a hydrogen atom or a methyl group.

  Specific examples of the formula (4) include the following formulas (4-1) to (4-4).

Is mentioned. Of these, monomers represented by the formulas (4-1), (4-3), and (4-4) are preferable from the viewpoint of sensitivity and resolution. R represents a hydrogen atom or a methyl group.

  Specific examples of the formula (5) include the following formulas (5-1) to (5-10).

Is mentioned. Among these, from the viewpoint of sensitivity and resolution, the monomer represented by the formula (5-1) is preferable. R represents a hydrogen atom or a methyl group.

  Specific examples of the formula (6) include the following formulas (6-1) to (6-4).

Is mentioned. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (7), the following formulas (7-1) to (7-10)

Is mentioned. Among them, the monomers represented by the formulas (7-1) to (7-3) and the formulas (7-6) to (7-8) are preferable from the viewpoint of excellent solubility in organic solvents. The monomer represented by the formula (7-2) is more preferable from the viewpoint of high dry etching resistance required for the resist.

  In the method of the present invention, the lactone used as a polymerization solvent is a cyclic saturated hydrocarbon containing an intracyclic carboxyl group, and may have a linear or branched saturated hydrocarbon substituent on the ring. Good compound. Specific examples include β-butyrolactone, γ-butyrolactone, α-methyl-γ-butyrolactone, and the like. Among them, γ-butyrolactone having a low boiling point is preferable.

As a solvent that can be used as a polymerization solvent together with the above lactones, a solvent that can dissolve both the monomer, a polymerization initiator, and a chain transfer agent when the chain transfer agent is used in combination is preferable. . Examples of such an organic solvent include 1,4-dioxane, isopropyl alcohol, acetone, tetrahydrofuran (hereinafter sometimes referred to as THF), methyl ethyl ketone (hereinafter sometimes referred to as MEK), methyl isobutyl ketone, and propylene. Examples thereof include glycol monomethyl ether acetate (hereinafter sometimes referred to as PGMEA) and ethyl lactate. These solvents can be used alone or in combination of two or more as required.

  In the present invention, changing the abundance ratio of lactones in the polymerization solvent (hereinafter also referred to as “concentration”) means that the concentration of lactones in the polymerization solvent is continuously changed between the start of the polymerization reaction and the end of the polymerization reaction. This also includes the case of changing to, or the case of changing intermittently. Further, it means that the concentration of lactones in the polymerization solvent increases or decreases with the progress of the polymerization reaction. Further, when the concentration of lactones in the polymerization solvent is increased as the polymerization reaction proceeds, the concentration of lactones dropped or introduced into the polymerization reaction solution is set higher than the concentration of lactones already present in the polymerization vessel. A mixed solvent containing lactones or a single lactone can be used. On the other hand, when the concentration of lactones is lowered as the polymerization reaction proceeds, the concentration of lactones dropped or introduced into the polymerization reaction solution should be lower than the concentration of lactones already present in the polymerization vessel. A mixed solvent containing lactones or a single solvent other than lactones can be used. The “mixed solvent” defined in the present invention is only required to be a mixed solvent at the end of the polymerization reaction, and includes the case where it is a single solvent of lactones or a single solvent other than lactones at the initial stage of the reaction. .

  The mixing ratio of lactones and other solvents is, for example, in the case of a mixed solvent of γ-butyrolactone and THF, preferably from 28.5 to 100% by mass of γ-butyrolactone, and in the case of a mixed solvent of γ-butyrolactone and PGMEA Γ-butyrolactone is preferably 3.3 to 100% by mass, but the combination of lactones and other solvents is not limited thereto.

  The concentration change amount of the lactone is preferably 3% by mass to 20% by mass per hour from the viewpoint of the consumption rate of the monomer having a lactone skeleton during the polymerization reaction.

  The reason why the use of the resist copolymer obtained by the production method of the present invention exhibits excellent performance such as generation of microgel in the resist solution and reduction of line edge roughness will be described below. It is estimated as follows.

  That is, the resist copolymer obtained by the conventional production method in which the concentration of the lactone as a solvent with respect to the polymerization solvent does not change is a chain of structural units having a lactone skeleton in one molecular chain. Since the length is long, the structural unit chain distribution becomes nonuniform in the resist copolymer as a whole, and a microgel is generated in the resist solution. Further, if the structural unit chain distribution is non-uniform, the distribution of protecting groups that are eliminated by an acid on the resist film surface and in the inside becomes non-uniform, thereby resulting in poor line edge roughness.

  In contrast, the resist copolymer obtained by the production method of the present invention can control the chain distribution of structural units having a lactone skeleton by changing the concentration of the lactone as a solvent with respect to the polymerization solvent. As a result, the chain distribution of other structural units can also be controlled, and the chain length of the same structural unit in one molecular chain is shorter than that of the prior art, and the structural unit chain distribution as a whole resist copolymer Becomes uniform and the copolymer composition distribution becomes narrow, thereby solving the problems found in the prior art.

  That is, the present invention is based on the finding that the consumption rate of a monomer having a lactone skeleton relatively decreases as the concentration of lactones in a solvent increases.

  When this is applied, in the copolymerization of a monomer having a lactone skeleton with another monomer, if the consumption rate of the monomer having a lactone skeleton is relatively high, the lactone in the solvent at the initial stage of polymerization The chain length of the monomer having a lactone skeleton can be shortened by increasing the concentration of the monomer and decreasing the concentration of the lactone in the solvent as the polymerization proceeds. On the other hand, if the consumption rate of the monomer having a lactone skeleton is relatively slow, the concentration of lactones in the solvent is lowered at the beginning of the polymerization, and the concentration of lactones in the solvent as the polymerization proceeds. You can raise it.

  As described above, the monomer component copolymerized with the monomer having a lactone skeleton is preferably a monomer having an acid leaving group because it can be used as a chemically amplified resist. Examples of the acid leaving group include cyclic ether groups such as tertiary alkyl groups, tetrahydropyranyl groups and tetrahydrofuranyl groups, and alkoxyalkyl groups such as 1-ethoxyethyl group and 1-methoxypropyl group. .

  The monomer having an acid leaving group preferably contains an alicyclic skeleton in terms of dry etching resistance. The structural unit having an alicyclic skeleton is a structural unit skeleton having a structure having at least one cyclic aliphatic hydrocarbon group. This cyclic aliphatic hydrocarbon group may have a substituent.

  Examples of the (meth) acrylic monomer having an alicyclic skeleton include, for example, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tetracyclododecanyl (meth) acrylate, and tricyclodecanyl. (Meth) acrylate, dicyclopentadienyl (meth) acrylate, and derivatives having a substituent on the alicyclic skeleton of these compounds are preferred. In this alicyclic skeleton, the binding site with the (meth) acrylic acid unit may be a tertiary carbon to form an acid leaving group, or through a tertiary carbon atom such as a tert-butyl group. It may be combined with a (meth) acrylic acid unit.

  Resist copolymers containing (meth) acrylic monomers having an alicyclic skeleton are excellent in dry etching resistance, and these (meth) acrylic monomers have acid-eliminating groups. It has excellent sensitivity. Furthermore, when these (meth) acrylic monomers contain polar groups such as hydroxyl groups, they have excellent resist pattern shape stability.

  The monomer which has an acid leaving group can be used 1 type or in combination of 2 or more type as needed.

  The ratio of the structural unit having an acid leaving group is preferably in the range of 10 to 90 mol%, more preferably in the range of 30 to 70 mol% with respect to the entire copolymer. As the ratio of the structural unit having an acid-eliminable group increases, the sensitivity and resolution improve, and as the ratio decreases, the adhesion to the metal surface or the like decreases.

  In the present invention, a monomer having an alicyclic skeleton represented by the above formulas (8) to (11) is preferable as the monomer having an acid leaving group. Specific examples of the formula (8) include the following formulas (8-1) to (8-4).

Is mentioned. Especially, the monomer represented by said Formula (8-1), said Formula (8-2), and said Formula (8-4) from the point of a sensitivity and the resolution is preferable. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (9), the following formulas (9-1) to (9-10)

Is mentioned. Among these, from the viewpoint of sensitivity and resolution, the monomer represented by the formula (9-1) is preferable. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (10), the following formulas (10-1) to (10-8)

Is mentioned. Among these, from the viewpoint of sensitivity and resolution, monomers represented by the formula (10-1), the formula (10-2), the formula (10-5), and the formula (10-6), and these Of the monomers represented by the above formula (10-5) and the above formula (10-6), and their geometric isomers, optical, and the like. Isomers are preferred. R represents a hydrogen atom or a methyl group.

  As specific examples of the formula (11), the following formulas (11-1) to (11-8)

Is mentioned. Among these, from the viewpoint of excellent sensitivity and resolution, monomers represented by the formula (11-1), the formula (11-2), the formula (11-5), and the formula (11-6) are preferable. . Moreover, the monomer represented by said Formula (11-5)-(11-6) is preferable from the point which is excellent in resist pattern rectangularity. R represents a hydrogen atom or a methyl group.

  In the method for producing a resist copolymer of the present invention, when the obtained copolymer is used for ArF excimer laser lithography, both an acid-eliminating monomer and a monomer having a lactone skeleton are used. It is preferable to use a monomer having a polar group because it is excellent in pattern shape rectangularity.

  The monomer having a polar group is a monomer having at least one of a hydroxyl group, a cyano group, an amino group, and an anhydrous carboxy group, and having an ethylenic double bond as a polymerizable functional group. . By using such a monomer for the copolymerization reaction, a copolymer containing a structural unit having a polar group can be obtained.

  Monomers having a polar group can be used alone or in combination of two or more.

  The ratio of the structural unit having a polar group in the copolymer (excluding those containing a lactone skeleton or an acid leaving group) is preferably in the range of 2 to 50 mol%, more preferably in the range of 5 to 40 mol%. preferable.

  Examples of the monomer having such a polar group include hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, cyanonorbornyl (meth) acrylate, hydroxyadamantyl (meth) acrylate, ( (Meth) acrylic acid cyanotricyclodecanyl, (meth) acrylic acid hydroxytricyclodecanyl, maleic anhydride, itaconic anhydride, (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) Examples include acrylamide, a monomer having a substituent on the cyclic hydrocarbon group of these compounds, and p-hydroxystyrene.

  Specific examples of the monomer having a polar group include monomers represented by the following formulas (12-1) to (12-18).

Is mentioned. Among these, the above formulas (12-4) to (12-13) are preferable from the viewpoint of high dry etching resistance required for the resist. R represents a hydrogen atom or a methyl group.

  In the method for producing a resist copolymer of the present invention, a vinyl monomer other than a monomer having an acid leaving group, a monomer having a lactone skeleton, and a monomer having a polar group (Hereinafter referred to as “another vinyl monomer”) may be used.

  Other vinyl monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid-n-propyl, (meth) acrylic Acid-iso-propyl, (meth) acrylic acid-n-butyl, (meth) acrylic acid-iso-butyl, (meth) acrylic acid-tert-butyl, (meth) acrylic acid methoxymethyl, (meth) acrylic acid- n-propoxyethyl, (meth) acrylic acid-iso-propoxyethyl, (meth) acrylic acid-n-butoxyethyl, (meth) acrylic acid-iso-butoxyethyl, (meth) acrylic acid-tert-butoxyethyl, ( (Meth) acrylic acid-2-ethoxyethyl, (meth) acrylic acid-1-ethoxyethyl, (meth) acrylic acid-2,2,2-trifluoroethyl, (meth) acrylic acid-2,2,3 , 3-tetrafluoro-n-propyl, (meth) acrylic acid-2,2,3,3,3-pentafluoro-n-propyl, etc. Tri) fluoromethyl (meth) acrylate methyl, α- (tri) fluoromethyl ethyl (meth) acrylate, α- (tri) fluoromethyl (meth) acrylate-2-ethylhexyl, α- (tri) fluoromethyl ( Meth) acrylic acid-n-propyl, α- (tri) fluoromethyl (meth) acrylic acid-iso-propyl, α- (tri) fluoromethyl (meth) acrylic acid-n-butyl, α- (tri) fluoromethyl (Meth) acrylic acid-iso-butyl, α- (tri) fluoromethyl (meth) acrylic acid-tert-butyl, α- (tri) fluoromethyl (meth) acrylic acid methoxymethyl, α- (tri) full Ethoxyethyl romethyl (meth) acrylate, α- (tri) fluoromethyl (meth) acrylic acid-n-propoxyethyl, α- (tri) fluoromethyl (meth) acrylic acid-iso-propoxyethyl, α- (tri) Fluoromethyl (meth) acrylic acid-n-butoxyethyl, α- (tri) fluoromethyl (meth) acrylic acid-iso-butoxyethyl, α- (tri) fluoromethyl (meth) acrylic acid-tert-butoxyethyl, etc. Α-fluoro (meth) acrylic acid ester having a linear or branched skeleton structure; aromatic alkenyl compounds such as styrene, α-methylstyrene, vinyltoluene, etc .; non-acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc. Saturated carboxylic acid; vinyl chloride, ethylene, vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl Rupiroridon, and the like. These can be used alone or in combination of two or more as required. Further, when these monomers contain a protecting group that is eliminated by an acid, excellent sensitivity is obtained.

  Other vinyl monomers can be used as long as the properties of the resulting copolymer are not significantly impaired. The proportion of structural units derived from the vinyl monomer in the copolymer is preferably 20 mol% or less.

  In radical polymerization using a polymerization initiator, a radical form of the polymerization initiator is generated in the reaction solution, and the chain polymerization of monomers proceeds from this radical form as a starting point. The polymerization initiator used for the production of the resist copolymer of the present invention is preferably one that generates radicals efficiently by heat. Examples of such a polymerization initiator include azo compounds such as 2,2′-azobisisobutyronitrile and dimethyl-2,2′-azobisisobutyrate; 2,5-dimethyl-2,5- And organic oxides such as bis (tert-butylperoxy) hexane. Moreover, when producing the copolymer for lithography using an ArF excimer laser light source, what does not have an aromatic ring in a molecular structure is preferable so that light transmittance may not be reduced as much as possible. Furthermore, in consideration of safety during polymerization, the polymerization initiator preferably has a 10-hour half-life temperature of 60 ° C. or higher.

  A chain transfer agent may be used when producing the resist copolymer. The advantage of using a chain transfer agent is that the amount of the polymerization initiator can be reduced when the low molecular weight copolymer is produced, and the molecular weight distribution of the copolymer can be reduced. Suitable chain transfer agents include, for example, 1-butanethiol, 2-butanethiol, 1-octanethiol, 1-decanethiol, 1-tetradecanethiol, cyclohexanethiol, 2-methyl-1-propanethiol, 2-mercapto Examples include ethanol.

  In the polymerization reaction, a polymer having a radical at the growth end is generated in the reaction solution. However, when a chain transfer agent is used, the radical at the growth end draws hydrogen from the chain transfer agent and becomes a polymer in which the growth end is deactivated. Become. On the other hand, the chain transfer agent from which hydrogen has been extracted has a structure having radicals, and the radical forms the starting point, and the monomer is chain-polymerized again. Therefore, a chain transfer residue exists at the terminal of the obtained polymer. When producing a copolymer for lithography using an ArF excimer laser light source, it is preferable to use a chain transfer agent having no aromatic ring so as not to reduce the light transmittance of the copolymer as much as possible.

  The method for producing the polymer of the present invention is not particularly limited, but a polymerization method called drop polymerization, which is generally performed by solution polymerization and a monomer is dropped into a polymerization vessel, is preferable.

  Among them, from the viewpoint that a polymer having a narrow composition distribution and / or molecular weight distribution can be easily obtained, a monomer that becomes a constituent unit of a target polymer by polymerization (even if only a monomer is used, The polymer of the present invention is preferably produced by a polymerization method called dropping polymerization in which the polymerization is carried out while dropping the solution in an organic solvent.

In the drop polymerization method, for example, an organic solvent is previously charged in a polymerization vessel and heated to a predetermined polymerization temperature, and then a monomer, a polymerization initiator, and a chain transfer agent dissolved in an organic solvent if necessary The body solution is dropped into the organic solvent in the polymerization vessel. The monomer may be dropped without being dissolved in the organic solvent. In that case, a solution in which the polymerization initiator and, if necessary, the chain transfer agent are dissolved in the monomer is dropped into the organic solvent. Further, the monomer may be dropped into the polymerization vessel without previously charging the organic solvent into the polymerization vessel. Moreover, a monomer, a polymerization initiator, and a chain transfer agent can each be dripped individually or in arbitrary combinations. The polymerization temperature in the dropping polymerization method is not particularly limited, but is preferably in the range of 50 to 150 ° C.

Although the density | concentration of the monomer solution dissolved in the organic solvent is not specifically limited, It is preferable to exist in the range of 5-50 mass%.
The copolymer of the present invention and the copolymer obtained by the production method of the present invention are characterized by a narrow copolymer composition distribution, thereby exhibiting excellent properties when used as a resist composition. The copolymer composition distribution can be obtained simply, rapidly and accurately by the method described below.
A method for measuring the copolymer composition distribution of the resist polymer using the critical adsorption chromatography method will be described.
The analysis method of the copolymer composition distribution of the resist copolymer using the critical adsorption chromatography method is based on a liquid phase chromatography (LC) method, and a commercially available LC apparatus can be used.
In the critical adsorption chromatography method, a mixture of a good solvent and a poor solvent (eluent) of a copolymer as a sample is used as a moving layer, inorganic and organic gels are used as a fixed layer, a sample, a gel, a sample, and an eluent In this method, the components are separated and detected by the polar distribution of one polymer chain of the copolymer as a sample, that is, the copolymer composition distribution, utilizing the interaction generated between the two. The eluent serving as the moving layer is pressure-fed at a constant flow rate by a constant-rate liquid feed pump. Inorganic and organic gels, which are fixed layers, are packed into a (for analysis) column and used. A typical LC system consists of an eluent tank, a pump, a switching valve, a sampling loop, a switching valve, a guard column, an analytical column, a detector, and a waste liquid tank in the order in which the eluent flows. ing.
A resist copolymer to be measured for the copolymer composition distribution is dissolved in a solvent in which the copolymer is completely dissolved to prepare a sample. The solvent to be used is not particularly limited as long as it is a good solvent for the resist copolymer or a mixed solvent in which the resist copolymer is completely dissolved in a mixture of the good solvent and the poor solvent. For example, water, methanol, ethanol , Alcohol solvents such as isopropanol, chlorine solvents such as carbon tetrachloride, chloroform, methylene chloride, chlorobenzene and dichlorobenzene, nitrile solvents such as acetonitrile, hydrocarbon solvents such as hexane, heptane and cyclohexane, benzene, toluene, Aromatic solvents such as xylene, acetate solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as diethyl ether, diisopropyl ether, 1,4-dioxane, tetrahydrofuran, N, N-dimethyl Formamide, N, N-amide solvent such as dimethylacetamide, sulfo solvents such as dimethyl sulfoxide, nitrogen-containing aromatic solvents such as pyridine, can be used weakly acidic solvent such as acetic acid. These solvents may be deuterated. Further, when preparing the sample, the resist copolymer may be dissolved after being dried in solid form, or the polymer solution after polymerization may be diluted with the above-mentioned solvent. The concentration of the sample is usually 0.05 to 10 mg / mL, preferably 0.1 to 5 mg / mL. If the sample concentration is too low, the detection sensitivity will decrease and the analysis accuracy will decrease, or the sample will be difficult to prepare.If the sample concentration is too high, the signal will exceed the measurement limit of the detector. This is not preferable because the analysis accuracy is lowered due to the excessively high value. The amount of the sample injected into the LC device is usually 5 to 200 μL, preferably 10 to 100 μL. If the amount of sample is too small, there will be a problem that the detection sensitivity will decrease or the accuracy of sample injection will decrease and the analysis accuracy will decrease.If the amount of sample is too large, the signal will exceed the measurement limit of the detector. This is not preferable because the analysis accuracy is lowered due to the excessively high value. The amount of the sample can be set to a desired amount by the LC apparatus.
The eluent used as the moving layer separates the copolymer composed of two or more kinds of structural units having different polarities according to the chemical composition ratio. It is necessary to use it. Therefore, a good solvent of the resist copolymer to be measured for the copolymer composition distribution or a mixed solvent in which the resist copolymer is completely dissolved in a mixture of the good solvent and the poor solvent is used. The same solvent as that used for preparing the mixture is used, but the mixing composition ratio is not particularly limited when mixed and used. The eluent is usually sent by a metering pump at a flow rate of 0.1 to 2.0 mL / min, preferably 0.2 to 1.0 mL / min. If the flow rate is small, the analysis time becomes long, and if the flow rate is large, the analysis accuracy is deteriorated. The liquid feeding accuracy of the metering liquid pump is usually within about ± 1.0% to about ± 0.5%. In addition, since the eluent used is a mixture of two or more types of solvents, a quantitative liquid feeding pump capable of mixing two or more types of solvents at an arbitrary ratio or changing the mixing ratio with time. Two or more units are preferably provided. Moreover, in order to mix two or more types of solvents uniformly, it is preferable to provide a mixing column between the metering liquid pump and the switching valve. Furthermore, it is preferable to provide a deaeration device between the eluent tank and the metered liquid feed pump because minute bubbles present in the eluent are removed and the liquid feed speed is stabilized.
The eluent sent out by the fixed liquid feed pump is sent to the analytical column, but there is a sample injection mechanism in front of the analytical column. The sample injection mechanism has a configuration of switching valve + sampling loop + switching valve. The sampling loop is a part for temporarily storing the sample. In a state where the eluent constantly flows, the eluent is sent to the analytical column without passing through the sampling loop. At the time of sample injection, a switching valve provided on both sides of the sampling loop is switched to the sample side, so that the sample in the sampling loop is sent to the analytical column.
In the method for analyzing a copolymer composition distribution of the present invention, the capacity of the sampling loop is usually 10 to 200 μL, preferably 10 to 50 μL. The sampling loop capacity is set by replacing the sampling loop with a desired capacity. For example, 10, 20, 50, 100 and 200 μL sampling loops are commercially available from Tosoh Corporation. The volume of the sampling loop to be used is determined by a ratio to the amount of sample (here, sampling loop volume / sample amount = sampling loop volume ratio). The sampling loop capacity ratio is usually 1 to 10, preferably 1 to 5, and particularly preferably 1 to 3. When the amount of sample, the volume of the sampling loop, and the volume ratio of the sampling loop are within the above ranges, the volume balance is excellent and the analysis accuracy of the copolymer composition distribution of the resist copolymer is good.
A guard column is disposed between the analysis column and the sample injection mechanism as necessary. The guard column is, for example, for removing unnecessary components and foreign matters in the eluent in the sample and preventing the analysis column from deteriorating.
As the fixed layer, an inorganic or organic gel is packed in a column (in the present invention, also referred to as “analysis column” in order to be distinguished from the guard column). The total length of the analytical column is usually 10 to 50 cm, more preferably 10 to 40 cm. For example, when one 15 cm column is used, it is preferably 1 to 3 in series, particularly preferably one. The inner diameter of the column is not particularly limited, but is usually 7 mm or less, preferably 5 mm or less. The inorganic or organic gel can be selected according to the polarity of the sample to be measured, such as silica gel, polyvinyl alcohol gel, polyhydroxyacrylate gel, polyacrylate gel, polystyrene-divinylbenzene gel, alumina, and carbon. Moreover, you may use what gave the chemical modification with a C4-C18 alkyl chain, a phenyl group, a cyano group, an amino group, a sulfo group, diol, a glyceropropyl group, etc. with respect to said stationary phase. . Among these, silica gel, polyacrylate gel, and polystyrene-divinylbenzene gel chemically modified with an alkyl chain having 4 to 18 carbon atoms are preferable from the viewpoint that the analysis accuracy of the copolymer composition distribution of the resist copolymer is good.
The inorganic or organic gel is in the form of particles, but the particle size is usually 20 μm or less, preferably 10 μm or less. The particle size is a value in a tetrahydrofuran (hereinafter sometimes referred to as THF) solvent because the degree of swelling varies depending on the type of eluent. An inorganic or organic gel having such a particle size is commercially available from a liquid chromatography apparatus company or the like.
By using the above inorganic or organic gel as a filler over the entire length of the analytical column, the balance of the interaction between the inorganic or organic gel and the resist copolymer is improved, the analytical accuracy is good, and the time required is short. It becomes possible to analyze the copolymer composition.
Since the sample flowing out from the analytical column is separated by the polarity of one polymer chain of the copolymer, the proportion of each copolymer composition fraction component is detected by detecting this with an appropriate detector. it can. As detectors, UV / Vis absorbance (UV-Vis) detector, fluorescence detector, differential refractive index (RI) detector, multi-wavelength detector, conductivity detector, electrochemical detector, evaporative light scattering detection (ELSD), mass spectrometer (MSD), nuclear magnetic resonance (NMR) apparatus, infrared (IR) spectrophotometer and the like. Among them, ELSD is preferable because it can be used even when the eluent has low light transmittance in the ultraviolet light and visible light regions. Also, NMR is preferred because the copolymer composition can be determined directly. A data processor is connected to the detector, and the copolymer composition distribution is quantified by a method described later, usually using a computer or the like.
The analytical column and preferably the detector are placed in a constant temperature bath and maintained at a constant temperature. This is to eliminate disturbance of measurement accuracy when measuring molecular weight as much as possible and improve analysis accuracy. The column is usually maintained at a temperature slightly higher than room temperature to room temperature, and the temperature control accuracy is preferably ± 0.2 ° C. or less, particularly preferably ± 0.1 ° C. or less.

Next, a method for analyzing the composition distribution of a copolymer using the critical adsorption chromatography method of the present invention will be described. Here, for simplicity, a copolymer composed of two types of structural units will be described.
Here, for simplicity, a copolymer UT composed of two types of structural units u and t will be described.
First, polymers (hereinafter referred to as homopolymers) U and T having only three structural units having three or more different mass average molecular weights are prepared. The method for producing the homopolymer is not particularly limited, such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. However, since the molecular weight control is easy and the molecular weight distribution is relatively narrow, solution polymerization is preferable. In order to remove impurities contained in the homopolymer, a reprecipitation purification operation is preferably performed. Furthermore, in order to obtain samples having different mass average molecular weights, homopolymers having a certain mass average molecular weight may be subjected to molecular weight fractionation by known methods such as solvent fractionation, precipitation fractionation, and chromatographic fractionation. The polymerization initiator, depending on the case, the molecular weight modifier or chain transfer agent, and the polymerization solvent are not particularly limited.
Next, the type and composition ratio of the eluent, the analytical column, and the column temperature are determined so that the top points of the elution curves of the respective homopolymers U having different mass average molecular weights coincide. The measurement conditions (type of eluent, composition ratio, analytical column, column temperature) at this time are defined as critical adsorption conditions for the homopolymer U (hereinafter referred to as CA conditions). Similarly, although the CA conditions for the homopolymer T are determined, the type of eluent and the analytical column are preferably the same as those for the homopolymer U. As the eluent, a solvent that completely dissolves the homopolymers U and T is used. The column temperature is preferably 60 ° C. or lower because the eluent does not decompose or volatilize, and preferably 0 ° C. or higher because the viscosity of the eluent is low.
And among the CA conditions of the homopolymers U and T, the CA conditions of the homopolymer with a slow time at which the top point of the elution curve appears from the CA conditions of the homopolymer with a fast time at which the top point of the elution curve appears. When liquid phase chromatography is performed using a solution of the copolymer UT as a sample under measurement conditions that are changed at a constant rate (hereinafter referred to as “composition distribution measurement conditions”), the copolymer composition ratio of the copolymer UT is obtained. A corresponding elution curve can be obtained.
However, depending on the combination of structural units, it may not be possible to find CA conditions in which both the type of eluent and the analytical column are common. In such a case, it is possible to obtain an elution curve by fixing the measurement under the CA condition of one of the structural units.
The elution curve of the copolymer UT thus obtained can correspond to the elution time and the copolymer composition by any one of the following three methods. The elution curve can be read as a copolymer composition distribution curve.
Method 1: Method using NMR as a detector In this method, a sample of copolymer UT separated by an analytical column is directly introduced into an NMR apparatus, and an NMR spectrum obtained by performing NMR measurement at regular intervals, By obtaining the copolymer composition ratio, the elution time is replaced with the copolymer composition ratio. The interval for NMR measurement is preferably within 30 seconds from the point that the copolymer composition distribution curve becomes smooth.
Method 2: Method for Measuring Copolymerization Composition Ratio of Fractionated Sample by NMR In the above Method 1, a sample of copolymer UT separated by an analytical column was directly introduced into an NMR apparatus. In this method, the sample of the separated copolymer UT is once fractionated into several types, and then the fractionated sample is subjected to NMR measurement to obtain a copolymer composition ratio for each fraction. The elution time is replaced with the copolymer composition ratio. The interval for fraction collection is preferably within 30 seconds from the point that the copolymer composition distribution curve becomes smooth.
Method 3: Using a Sample with a Known Copolymerization Composition Ratio as a Standard Several types of samples with different copolymerization composition ratios (hereinafter referred to as “standard samples”) are measured under the above-described composition distribution measurement conditions and obtained with each standard sample The time at the top of the elution curve is replaced with the copolymer composition ratio. The standard sample is preferably one having as little copolymer composition distribution as possible.
Of the above three methods, Method 1 or Method 2 is preferable from the viewpoint of more accurate copolymer composition distribution curve, and Method 3 is preferable because no special apparatus is required.
When the elution curve thus obtained is wide, it indicates that the copolymer composition distribution is wide, and conversely, when the elution curve is sharp, it indicates that the copolymer composition distribution is narrow.
The reliability of the measurement is judged by measuring the composition of the eluent sampled at a specific elution time around the apex point three times by NMR, and the error of each component is within ± 0.2%. be able to.
The average copolymer composition ratio of the structural unit having a lactone skeleton of the copolymer is a copolymer composition ratio calculated using the peak intensity of the monomer unit having a lactone skeleton in the spectrum obtained by NMR measurement. That's it. Note that the nucleus to be observed in the NMR measurement needs to be either ¹ H or ¹³ C. The sample concentration during NMR measurement is preferably 0.1 to 10 (mass / volume)%, more preferably 0.2 to 7 (mass / volume)% when the observation nucleus is ¹ H, and the observation nucleus is ^In the case of ¹³ C, 1 to 40 (mass / volume)% is preferable, and 5 to 30 (mass / volume)% is more preferable.
The area (P) of the copolymer composition distribution curve delimited by -5 mol% to +5 mol% of the average copolymer composition (X, unit mol%) of the structural unit (A) is the diagonal line of the elution curve below. It is the area of the part shown.
The total area of the copolymer composition distribution curve is the area (Q) surrounded by the elution curve and the baseline in the elution curve below.
Therefore, in the copolymer composition distribution curve, the entire area of the copolymer composition distribution curve divided in the range of −5 mol% to +5 mol% of the average copolymer composition ratio of the structural unit having a lactone skeleton of the resist copolymer. The ratio to is obtained by (P / Q) × 100 [%], and this needs to be 42 to 95%. A larger value means that the copolymer composition distribution is narrower. Preferably, the lower limit is 50% or more.

  The mass average molecular weight of the resist copolymer of the present invention is not particularly limited, but the lower limit is preferably 1,000 or more, more preferably 2,000 or more, and more preferably 4,000 or more. Further preferred. The upper limit is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. If the mass average molecular weight is larger than this, the solubility in the resist solution is lowered and the resolution is lowered. If the mass average molecular weight is smaller than this, the dry etching resistance tends to decrease and the resist shape tends to deteriorate.

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

  The resist copolymer solution produced by a method such as solution polymerization is suitable as it is or in a good solvent such as 1,4-dioxane, acetone, tetrahydrofuran, methyl isobutyl ketone, γ-butyrolactone, PGMEA, ethyl lactate, etc. After diluting to a proper solution viscosity, the solution is dropped into a large amount of poor solvent such as methanol or water to precipitate a resist copolymer.

  This step is generally called “reprecipitation” and may be unnecessary in some cases, but is very effective for removing unreacted monomers remaining in the polymerization solution, polymerization initiators, and the like. If these unreacted substances remain as they are, there is a possibility of adversely affecting the resist performance. Therefore, it is preferable to remove them as much as possible.

  Then, the resist copolymer of the present invention can be obtained by filtering the precipitate and drying it sufficiently. Moreover, after filtering off, it can also be used with a moist powder without drying. Further, the produced copolymer solution can be used as a resist composition as it is or after being diluted with an appropriate solvent. At that time, additives such as a storage stabilizer may be appropriately added.

  The resist composition of the present invention is obtained by dissolving the resist polymer of the present invention as described above in a solvent. The chemically amplified resist composition of the present invention is obtained by dissolving the resist polymer of the present invention and a photoacid generator as described above in a solvent. The resist polymer of the present invention may be used alone or in combination of two or more. In addition, without separating the polymer from the polymer solution obtained by solution polymerization or the like, this polymer solution can be used as it is in the resist composition, or the polymer solution can be diluted with an appropriate solvent to form a resist. It can also be used in a composition.

  These solvents are arbitrarily selected according to the purpose, but the selection of the solvent may be restricted by reasons other than the solubility of the resin, for example, uniformity of the coating film, appearance, safety, and the like.

Solvents usually used for preparing the resist composition 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 Propylene glycol monoalkyl acetates such as acetate, ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether Diethylene glycol alkyl such as diethylene glycol dimethyl ether and diethylene glycol monomethyl ether Ethers, esters such as ethyl acetate and ethyl lactate, alcohols such as n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, cyclohexanol and 1-octanol, 1, Examples include 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 used is usually 200 parts by mass or more and more preferably 300 parts by mass or more with respect to 100 parts by mass of the resist polymer (copolymer of the present invention). Moreover, the usage-amount of a solvent is 5000 mass parts or less normally with respect to 100 mass parts of resist polymers (copolymer of this invention), and it is more preferable that it is 2000 mass parts or less.

  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 that can be used as the acid generator of the chemically amplified resist composition.

  Examples of such a photoacid generator include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonic acid ester compounds, quinonediazide compounds, and diazomethane compounds. Of these, onium salt compounds such as sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts are preferred.

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

  A photo-acid generator can be used individually or in mixture of 2 or more types.

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

  When the amount of the photoacid generator used 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 is increased. This is preferable because it can prevent the occurrence of uneven coating during coating of the composition and scum during development.

  Furthermore, various additives such as surfactants, quenchers, sensitizers, antihalation agents, storage stabilizers, antifoaming agents, and the like can be blended with the resist composition of the present invention as necessary. Any of these additives can be used as long as it is known in the art. Moreover, the compounding quantity of these additives is not specifically limited, What is necessary is just to determine suitably.

  Next, an example of the pattern forming 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 formed by spin coating or the like. And the to-be-processed board | substrate with which this resist composition was apply | coated is dried by baking process (prebaking) etc., and a resist film is formed on a board | substrate.

Next, the resist film thus obtained is irradiated with light or an electron beam having a wavelength of 250 nm or less through a photomask (exposure). The light used for exposure is preferably KrF excimer laser light, ArF excimer laser light, or F ₂ excimer laser light, and particularly preferably ArF excimer laser light.

  After the exposure, heat treatment is appropriately performed (post-exposure baking, PEB), the substrate is immersed in an alkaline developer, and the exposed portion is dissolved and removed in the developer (development). Any known alkaline developer may be used. Then, after development, the substrate is appropriately rinsed with pure water or the like. In this way, a resist pattern is formed on the substrate to be processed.

  Usually, a substrate to be processed on which a resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist, and a portion without the resist is selectively etched. After etching, the resist is usually removed using a release agent.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In the examples and comparative examples, “parts” means “parts by mass” unless otherwise specified. Further, physical properties and the like in Examples and Comparative Examples were measured using the following methods.

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

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

(3) Sensitivity 100 parts of a copolymer for resist, 2 parts of triphenylsulfonium triflate as a photoacid generator, and 700 parts of PGMEA as a solvent are mixed to obtain a uniform solution, and then filtered through a membrane filter having a pore size of 0.1 μm. Then, a resist composition solution was prepared. Thereafter, this resist composition solution was spin-coated on a silicon wafer and pre-baked 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, post-exposure baking was performed using a hot plate at 120 ° C. for 60 seconds. Subsequently, it developed at room temperature using the 2.38 mass% tetramethylammonium hydroxide aqueous solution, wash | cleaned with the pure water, and dried, and the resist pattern was formed. Sensitivity was measured as the minimum exposure amount for forming a line-and-space (L / S = 1/1) with a line width of 1/1.

(4) Resolution The minimum dimension (μm) of the resist pattern that is resolved when the exposure amount is exposed is defined as the resolution.

(5) Number of microgels For the resist composition solution prepared as described above, the number of microgels in the solution immediately after preparation (initial value of microgel) and Michael gel in the solution after standing at 4 ° C. for 1 week (The number of microgels after time) was counted with a particle counter manufactured by Rion. Along with the initial value of the microgel, the number of increased microgels calculated by (number of microgels after time) − (initial value of microgel) was measured. The number of microgels having a particle size of 0.25 μm or more present in 1 ml of the resist composition solution was counted.

(6) Line edge roughness For the range of 5 μm side edge in the longitudinal direction of a 0.20 μm resist pattern produced using a 0.20 μm mask, the distance from the reference line where the pattern side edge should be 50 points were measured with a −6340F field emission scanning electron microscope, the standard deviation was obtained, and 3σ was calculated. A smaller value indicates better performance.

<Example 1>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, under a nitrogen atmosphere, 14.7 parts of propylene glycol monomethyl ether acetate (hereinafter sometimes referred to as PGMEA), γ-butyrolactone (hereinafter referred to as γ-) 6.7 parts) (sometimes referred to as BL), and the temperature of the hot water bath was raised to 80 ° C. with stirring. The γ-BL concentration at this point was 31.3 % by mass. β-methacryloyloxy-γ-butyrolactone (hereinafter sometimes referred to as HGBMA) 18.0 parts, 2-methacryloyloxy-2-methyladamantane (hereinafter sometimes referred to as MAdMA) 22.0 parts, PGMEA 60.0 From a dropping apparatus containing a monomer solution mixed with 0.82 part of 2,2′-azobisisobutyronitrile (hereinafter sometimes referred to as AIBN) in a flask at a constant rate for 6 hours. It was dripped. The γ-BL concentration at the end of dropping of the monomer solution was 20% by mass. Then, the temperature of 80 degreeC was hold | maintained for 1 hour. Subsequently, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer A-1). In order to completely remove the monomer remaining in the precipitate, the obtained precipitate was filtered and washed in about 30 times the amount of methanol with respect to the monomer used for the polymerization. The resulting precipitate was filtered off and dried under reduced pressure at 50 ° C. for about 40 hours. Table 1 shows the results obtained by measuring the physical properties of the obtained copolymer A-1.

<Example 2>
Under a nitrogen atmosphere, 20.0 parts of γ-BL 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. The γ-BL concentration at this point was 100 % by mass. 2-exo-methacryloyloxy-4-oxatricyclo [4.2.1.03,7] nonan-5-one (hereinafter sometimes referred to as NLMA) 26.2 parts, MAdMA 29.1 parts, PGMEA 24. From a dropping device containing a monomer solution in which 8 parts, γ-BL 37.8 parts, tert-butyl peroxyisobutyrate 0.30 part, and n-butyl mercaptan 0.90 part were mixed, at a constant rate, 6 hours. And dropped into the flask. The γ-BL concentration at the end of dropping of the monomer solution was 25% by mass. Then, the temperature of 80 degreeC was hold | maintained for 30 minutes. Next, after the obtained reaction solution was diluted with 2 times amount of γ-BL, it was dropped into about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer A-2). It was. The subsequent operations were performed in the same manner as in Example 1, and the results of measuring the physical properties of the copolymer A-2 obtained are shown in Table 1.

< Reference Example 3>
Under a nitrogen atmosphere, 31.2 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. The γ-BL concentration at this point was 0% by mass. 8- or 9-acryloyloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one (hereinafter sometimes referred to as OTDA) 19.5 parts, 2-methacryloyloxy- 2-ethyladamantane (hereinafter sometimes referred to as EAdMA) 18.4 parts, 1-methacryloyloxy-3-hydroxyadamantane (hereinafter sometimes referred to as HAdMA) 9.0 parts, PGMEA 53.1 parts, γ- 6 hours at a constant rate from a dropping apparatus containing a monomer solution mixed with 56.2 parts of BL and 2.76 parts of dimethyl-2,2′-azobisisobutyrate (hereinafter sometimes referred to as DAIB). And dropped into the flask. The γ-BL concentration at the end of dropping of the monomer solution was 40% by mass. Then, the temperature of 80 degreeC was hold | maintained for 1 hour. Next, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer A-3). The subsequent operations were performed in the same manner as in Example 1, and the results of measuring physical properties of the copolymer A-3 obtained are shown in Table 1.

<Example 4>
Under a nitrogen atmosphere, 14.3 parts of PGMEA and 20.5 parts of γ-BL were 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. At this time, the γ-BL concentration in the polymerization solvent was 59% by mass. α-methacryloyloxy-γ-butyrolactone (hereinafter sometimes referred to as GBLMA) 13.3 parts, EAdMA 20.3 parts, 2- or 3-cyano-5-norbornyl methacrylate (hereinafter sometimes referred to as CNNMA) ) From a dropping apparatus containing a monomer solution in which 8.2 parts, 53.9 parts of PGMEA, 8.8 parts of γ-BL, 1.32 parts of AIBN, and 0.30 parts of n-octyl mercaptan were added at a constant rate for 4 hours. And dropped into the flask. The γ-BL concentration in the polymerization solvent at the end of dropping of the monomer solution was 30% by mass. Then, the temperature of 80 degreeC was hold | maintained for 3 hours. Next, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer A-4). The subsequent operations were performed in the same manner as in Example 1, and the results of measuring the physical properties of the copolymer A-4 obtained are shown in Table 1.

<Comparative Example 1>
Under a nitrogen atmosphere, 26.6 parts of PGMEA and 6.6 parts of γ-BL were 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. The γ-BL concentration at this point was 20% by mass. From a dropping apparatus containing a monomer solution in which 18.4 parts of HGBMA, 21.5 parts of MAdMA, 47.9 parts of PGMEA, 12.0 parts of γ-BL, and 0.82 parts of AIBN were mixed, into the flask at a constant rate over 6 hours. It was dripped. The γ-BL concentration at the end of dropping of the monomer solution was 20% by mass. Then, the temperature of 80 degreeC was hold | maintained for 1 hour. Next, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer B-1). The subsequent operations are shown in Table 1 as a result of measuring physical properties of the copolymer B-1 obtained in the same manner as in Example 1.

<Comparative example 2>
Under a nitrogen atmosphere, 9.3 parts of PGMEA and 20.0 parts of γ-BL were 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. At this time, the concentration of γ-butyrolactone was 68.3 % by mass. A dropping device containing a monomer solution in which 26.9 parts of NLMA, 28.4 parts of MAdMA, 62.5 parts of γ-BL, 0.30 part of tert-butyl peroxyisobutyrate, and 0.90 part of n-butyl mercaptan are mixed. Then, it was dropped into the flask at a constant rate over 6 hours . Then, the temperature of 80 degreeC was hold | maintained for 30 minutes. Next, the resulting reaction solution was diluted with 2 times the amount of γ-BL and then added dropwise to about 30 times the amount of methanol with stirring to obtain a white precipitate (copolymer B-2). It was. The subsequent operations were performed in the same manner as in Example 1, and the results of measuring the physical properties of the copolymer B-2 obtained are shown in Table 1.

<Comparative Example 3>
Under a nitrogen atmosphere, 18.7 parts of PGMEA and 12.5 parts of γ-BL were 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. The γ-BL concentration at this point was 40% by mass. From a dropping apparatus containing a monomer solution in which 19.1 parts of OTDA, 18.8 parts of EAdMA, 9.0 parts of HAdMA, 65.6 parts of PGMEA, 43.7 parts of γ-BL and 2.76 parts of DAIB were added at a constant speed for 6 hours. And dropped into the flask. The γ-butyrolactone concentration at the end of dropping of the monomer solution was 40% by mass. Then, the temperature of 80 degreeC was hold | maintained for 1 hour. Next, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate (copolymer B-3). The subsequent operations were performed in the same manner as in Example 1, and the results of measuring the physical properties of the copolymer B-3 obtained are shown in Table 1.

As described above, in Examples 1 to 2 and 4, the formation of microgel in the resist solution was suppressed and the line edge roughness was improved without deteriorating the sensitivity and / or resolution. On the other hand, in Comparative Example 1, the formation of microgel in the resist solution was suppressed, but the line edge roughness was not improved. In Comparative Examples 2 and 3, many microgels were formed in the resist solution, and the line edge roughness was not improved.

<Example 5>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, in a nitrogen atmosphere, 6.2 parts of PGMEA and 32.7 parts of γ-butyrolactone were placed, and the temperature of the water bath was increased to 80 ° C. while stirring. Raised. At this time, the concentration of γ-butyrolactone was 84% by mass. From a dropping apparatus containing a monomer solution in which 24.4 parts of OTDA, 22.3 parts of EAdMA, 70.1 parts of PGMEA, 0.18 part of 1-octanethiol and 1.32 parts of AIBN were added, the flask was stirred at a constant speed for 6 hours. It was dripped in. The concentration of γ-butyrolactone immediately after the dropping was 30% by mass. Then, the temperature of 80 degreeC was hold | maintained for 1 hour. Next, the obtained reaction solution was added dropwise to about 10 times amount of methanol with stirring to obtain a white precipitate (copolymer A-5). The resulting precipitate was filtered off and dried under reduced pressure at 60 ° C. for about 40 hours. Table 2 shows a result obtained by measuring physical properties of the obtained copolymer A-5.

<Comparative example 4>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, under a nitrogen atmosphere, 26.6 parts of OTDA, 19.8 parts of EAdMA, 139.4 parts of PGMEA, and 2.62 parts of AIBN are placed in a total amount and stirred in a hot water bath. The temperature was raised to 80 ° C. and polymerization was carried out at that temperature for 7 hours. Subsequently, the obtained reaction solution was diluted about 2-fold with PGMEA. Thereafter, the same operations as in Example 5 were carried out, so as to obtain a copolymer B-4. Table 2 shows a result obtained by measuring properties of the obtained copolymer B-4.

<Comparative Example 5>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, 39.0 parts of PGMEA was placed in a nitrogen atmosphere, and the temperature of the hot water bath was raised to 80 ° C. while stirring, and polymerization was performed at that temperature for 7 hours. It was. Thereafter, the same operations as in Example 5 were carried out, so as to obtain a copolymer B-5. Table 2 shows a result obtained by measuring physical properties of the obtained copolymer B-5.

<Comparative Example 6>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, 27.3 parts of PGMEA and 11.7 parts of γ-butyrolactone were placed under a nitrogen atmosphere, and the temperature of the hot water bath was increased to 80 ° C. while stirring. Raised. At this time, the concentration of γ-butyrolactone was 30% by mass. From a dropping apparatus containing a monomer solution in which 24.4 parts of OTDA, 22.3 parts of EAdMA, 49.1 parts of PGMEA, 21.0 parts of γ-butyrolactone, 0.18 part of 1-octanethiol and 1.32 parts of AIBN were mixed. The solution was dropped into the flask over 6 hours at a constant speed. The concentration of γ-butyrolactone immediately after the dropping was 30% by mass. Subsequent operations were the same as those of Example 1, and copolymer B-3 was obtained. Table 2 shows a result obtained by measuring physical properties of the obtained copolymer B-6.

<Synthesis Example 1>
Synthesis of EAdMA homopolymers (EM-1, EM-2, EM-3, and EM-4) having different mass average molecular weights

A flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer was charged with 12.4 parts of EAdMA, 23.0 parts of THF, and 0.66 parts of AIBN under a nitrogen atmosphere, and the temperature of the hot water bath was 65 ° C. with stirring. And polymerized at that temperature for 7 hours. Next, the obtained reaction solution was diluted about 2 times with THF, and dropped into about 10 times amount of methanol with stirring to obtain a precipitate of a white precipitate (homopolymer EM-1). The resulting precipitate was filtered off and dried under reduced pressure at 60 ° C. for about 40 hours. The obtained homopolymer EM-1 was Mw = 2100 and Mw / Mn = 1.46.
Next, a homopolymer EM-2 with Mw = 4700 and Mw / Mn = 1.86 was obtained except that the amount of AIBN used was changed to 0.06 part.
Further, except that the amounts of THF and AIBN used were changed to 15.2 parts and 0.04 parts, respectively, the same operation as described above was carried out to obtain a homopolymer EM-3 having Mw = 8200 and Mw / Mn = 1.96. Obtained.
Then, except that the amounts of THF and AIBN used were changed to 10.1 parts and 0.04 parts, respectively, the same operation as described above was performed, and a homopolymer EM-4 having Mw = 13500 and Mw / Mn = 2.02 was obtained. Obtained.

<Measurement Example 1>
1 mg of each of the homopolymers EM-1, EM-2, EM-3, and EM-4, and the copolymer G for resist, and 1 mL of a mixed solvent of chloroform / acetonitrile = 80% by volume / 20% by volume. The sample solution of each homopolymer was prepared by mixing.
One eluent tank filled with chloroform (CLF) / acetonitrile (ATN) = 80 vol% / 20 vol%, which was ultrasonically degassed in advance, and a metered liquid feed pump PU-980 manufactured by JASCO Corporation, GL Sciences column jacket LCD-250 equipped with 100 μL sample loop, switching valve and column jacket temperature controller NESLAB RTE-111, and Phenomenex column KROMASIL5C4 (fixed layer: alkyl having 4 carbon atoms) It was composed of 5 μm diameter silica gel chemically modified with a chain, column: 250 mm length × 4.6 mm inner diameter separation column section, and an evaporative light scattering detector (ELSD) PL-EMD960 manufactured by Polymer Laboratories. Liquid chromatography (L ) In the apparatus, by introducing a sample solution 50μL of homopolymer EM-1 of EAdMA, it performs LC measurement was obtained elution curve of EM-1 in 20 minutes. The eluent flow rate was 0.2 mL / min, the column oven temperature was 24 ° C., and the ELSD gas flow rate and detection temperature were 7.2 L / min and 65 ° C., respectively.
The elution curves of the homopolymers EM-2, EM-3, and EM-4 were obtained in the same manner as described above for 20 minutes.
The top points of the elution curves of EM-1 to EM-4 coincided, and the above conditions became the critical adsorption conditions (CA conditions) for the homopolymer of EAdMA.
Then, under the CA conditions of the EAdMA homopolymer, coastal adsorption chromatography was performed using the resist copolymer A-5, B-4, and B-5 solutions as samples in the same manner as described above. A curve was obtained in 20 minutes, and P / Q was determined based on the curve. The results are shown in Table 2.

The resist polymer (Example 5) obtained by the production method of the present invention has a narrow copolymer composition distribution. The resist composition using this copolymer has sufficient sensitivity and resolution, and is developed. There were few defects at the time, and the formation of microgels in the resist solution was also small.
On the other hand, the polymers of Comparative Examples 4 and 5 had a wide copolymer composition distribution, and the resist composition using this polymer had many defects at the time of development, and many microgel formations in the resist solution were confirmed.

Claims (7)

And two or more monomers of the monomer and other monomer having a lactone skeleton, using a polymerization solvent containing a lactone, the abundance ratio of the lactone in the polymerization medium in the polymerization reaction Decrease in the range of 3-20% per hour with progress (however, in the polymerization reaction, the consumption rate of the monomer having the lactone skeleton is compared with the consumption rate of the other monomers) The polymerization solvent containing the lactones may have a linear or branched saturated hydrocarbon substituent on the ring, or a cyclic saturated solvent containing a carboxyl group in the ring. A method for producing a copolymer for resist, which is a hydrocarbon .   The method for producing a resist copolymer according to claim 1, comprising a monomer having an acid leaving group.   The production method according to claim 1, wherein, when producing the copolymer, the polymerization is performed while a solution in which at least one monomer is dissolved in an organic solvent is dropped into a polymerization vessel. In any one of claims 1 to 3 comprising a resist copolymer obtained by the production method described, the manufacturing method of the resist composition. A pattern manufacturing comprising: a step of applying a resist composition obtained by the method according to claim 4 on a substrate to be processed; a step of exposing with light having a wavelength of 250 nm or less; and a step of developing using a developer. Method. 6. The pattern manufacturing method according to claim 5 , wherein the light used for exposure is an ArF excimer laser. A pattern manufacturing method comprising a step of applying a resist composition obtained by the method according to claim 4 on a substrate to be processed, a step of exposing with an electron beam, and a step of developing using a developer.