Method for producing polymer

Abstract

[Problem] To provide a method for producing a highly pure resist polymer which exhibits excellent workability and which includes a structural unit having a phenolic hydroxyl group, a structural unit having an easily-acid-dissociable group, and a structural unit having a photoacid generation group. [Solution] A method for producing a polymer including a structural unit having a phenolic hydroxyl group, a structural unit having an acid-dissociable group, and a structural unit having a photoacid generation group, said method comprising: a step for polymerizing, in a solvent, a monomer having a structure in which a phenolic hydroxyl group is protected with at least an acetal group, a monomer having an acid-dissociable group, and a monomer having a photoacid generation group; and a deprotection step for removing the acetal group by bringing, in the absence of an acid having a pKa of not more than 8, a polymer obtained in the polymerization step into contact with a compound that is a proton source, wherein the rate of removal of the acetal group is not more than 98 mol%.

Description

Polymer manufacturing method

[0001] The present invention relates to a method for producing a polymer.

[0002] Microfabrication by photolithography has traditionally been used in semiconductor device manufacturing processes. For example, first, a thin film of a photolithography composition such as a photoresist or antireflective coating is formed on a semiconductor substrate such as a silicon wafer. Next, the substrate is irradiated with actinic light such as ultraviolet light through a mask pattern on which a semiconductor device pattern is drawn, and developed. The resulting photoresist pattern is used as a protective film to etch the substrate, thereby forming fine irregularities corresponding to the pattern on the substrate surface. In order to form such fine patterns, a resist composition with good lithography properties is required, and in order to improve the lithography properties of such resist compositions, high purity resist polymers are required.

[0003] Chemically amplified resist compositions having a base component whose solubility in a developer changes with the action of acid and an acid generator component that generates acid upon exposure have been used as resist compositions with good lithography properties. Resist polymers have also been proposed that incorporate structural units containing acid-generating groups that generate acid upon exposure as the acid generator component (see, for example, Patent Document 1). Such resist polymers function both as an acid generator and as a base component.

[0004] For resists, particularly resists for EUV, polymer compounds having structural units containing phenolic hydroxyl groups, structural units containing acid-dissociable groups (hereinafter referred to as acid-dissociable groups) that decompose under the action of acid to increase polarity, and structural units containing acid-generating groups (hereinafter referred to as photoacid-generating groups) that generate acid upon exposure are used as resist polymers that combine acid generator and base component functions. In particular, to improve the lithography properties of resists, structural units containing acid-dissociable groups that decompose more easily (hereinafter referred to as easily acid-dissociable groups) are used in place of the structural units containing acid-dissociable groups. Patent Document 2 discloses a method for producing a polymer compound having structural units containing phenolic hydroxyl groups and structural units containing acid-dissociable groups.

[0005] JP 2006-178317 A JP 2018-012823 A

[0006] However, a polymer compound having a structural unit containing a phenolic hydroxyl group and a structural unit containing an acid-dissociable group cannot be produced by the method reported in Patent Document 2. The reason for this is that when an acid component is added to the system to deprotect the protecting group of the phenolic hydroxyl group, decomposition of the acid-dissociable group also proceeds at the same time, resulting in a significant decrease in the purity of the target polymer compound. In response to this, a method of adding a base to the system to suppress decomposition of the acid-dissociable group is considered. However, when a base is added to the system, the photoacid-generating group reacts with the base, making it impossible to produce the target polymer compound containing a structural unit containing a phenolic hydroxyl group, a structural unit containing an acid-dissociable group, and a structural unit containing a photoacid-generating group.

[0007] Therefore, there is a need for a method for producing a high-purity resist polymer that functions as both an acid generator and a base component.

[0008] Furthermore, the present inventors have found that when a specific combination of monomers is used in producing the above polymer, the polymer precipitates during polymerization, resulting in poor workability. Therefore, there is a need for a method for producing the above polymer that not only produces a high-purity polymer but also ensures good workability.

[0009] Therefore, an object of the present invention is to provide a method for producing a resist polymer that is capable of producing a high-purity resist polymer that contains a structural unit having a phenolic hydroxyl group, a structural unit having an easily acid-dissociable group, and a structural unit having a photoacid-generating group, and that is also easy to work with.

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by polymerizing, in a solvent, a monomer having a structure in which a phenolic hydroxyl group is protected with an acetal group, a monomer having an acid-dissociable group, and a monomer having a photoacid-generating group, and then contacting the resulting polymer with a compound that serves as a proton source in the absence of an acid having a pKa of 8 or less, thereby deprotecting the acetal group in a specific ratio.

[0011] That is, the present invention provides the following inventions. [1] A method for producing a polymer containing a structural unit having a phenolic hydroxyl group, a structural unit having an acid-dissociable group, and a structural unit having a photoacid-generating group, comprising the steps of: polymerizing, in a solvent, a monomer having a structure in which the phenolic hydroxyl group is protected with at least an acetal group, a monomer having the acid-dissociable group, and a monomer having a photoacid-generating group; and a deprotection step of contacting the polymer obtained in the polymerization step with a compound that serves as a proton source in the absence of an acid having a pKa of 8 or less to deprotect the acetal groups, wherein the deprotection rate of the acetal groups is 98 mol % or less. [2] The method for producing a polymer according to [1], wherein the proton source in the deprotection step comprises at least one of an alcohol and a phenol. [3] The method for producing a polymer according to [2], wherein the alcohol has 6 or fewer carbon atoms. [4] The method for producing a polymer according to any one of [1] to [3], wherein the acid having a pKa of 8 or less is selected from the group consisting of acetic acid, oxalic acid, formic acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, malonic acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrobromic acid. [5] The method for producing a polymer according to any one of [1] to [4], wherein the deprotection rate of the acetal groups in the polymer in the deprotection step is 50 mol % or more. [6] The method for producing a polymer according to any one of [1] to [5], wherein the deprotection rate of the acetal groups in the polymer in the deprotection step is 95 mol % or less. [7] The method for producing a polymer according to any one of [1] to [6], further comprising a step of purifying the polymer obtained in the deprotection step using an alcohol-based solvent. [8] The method for producing a polymer according to [7], wherein the deprotection rate of the acetal groups in the polymer in the purification step is more than 98 mol %. [9] The method for producing a polymer according to any one of [1] to [8], wherein in the polymerization step, the content of the compound serving as a proton source contained in the polymerization solvent is 20 mass % or less of the total solvent.

[10] The method for producing a polymer according to any one of [1] to [9], wherein the monomer having a structure in which a phenolic hydroxyl group is protected with an acetal group includes a monomer having a structure in which a phenolic hydroxyl group of a compound represented by the following general formula (1) is protected with an acetal group represented by the following general formula (1-1): [In general formula (1), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １２ is a single bond or a divalent linking group which may have a hetero atom. n is an integer of 1 to 3. In general formula (1-1), R １３ and R １４ are each independently a hydrogen atom or an alkyl group. １５ is a hydrocarbon group. １５ is R １３ or R １４

[11] The monomer having an acid-dissociable group may be bonded to any one of the following general formula (2): [In general formula (2), R ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２２ represents a single bond or a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a hetero atom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a hetero atom. ２３ represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a heteroatom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a heteroatom. m is an integer of 0 to 2. R ２４ is an acid-dissociable group represented by the following general formula (2-1): [In general formula (2-1), R ２４１ represents a carbon atom. ２４２ is R ２４１ * represents a bond to the oxygen atom in formula (2). ２４３is an alkyl group or aromatic hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, or a group represented by the following general formula (2-1-1): In general formula (2-1-1), R ２４３１ , R ２４３２ and R ２４３３ are each independently a hydrogen atom or a saturated aliphatic hydrocarbon group. ２４３１ , R ２４３２ and R ２４３３ Two or more of the following may be bonded to each other to form a ring structure. * represents R in formula (2-1). ２４１

[12] The method for producing a polymer according to any one of [1] to

[10] , wherein the monomer having a photoacid generating group is represented by the following general formula (3): [In general formula (3), R ３１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ３２ is a single bond or an aromatic hydrocarbon group which may have a substituent. k is 0 or 1. R ３３ represents a single bond or a hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３４ represents a hydrocarbon group having 1 to 15 carbon atoms, and some or all of the hydrogen atoms in the hydrocarbon group may be replaced by fluorine atoms. ３５ , R ３６ and R ３７ each independently represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３５ , R ３６ and R ３７ any two or more of which may be bonded to each other to form a ring together with the sulfur atom in formula (3).

[0012] According to the present invention, a method for producing a resist polymer can be provided that can obtain a highly pure polymer and has excellent workability. Furthermore, since acid removal is not required, the process can be shortened, and since no acid is used, the risk of metal contamination can be reduced.

[0013] The following describes embodiments of the present invention, but it should be understood that the present invention is not limited to the following embodiments, and that appropriate modifications and improvements to the following embodiments based on the ordinary knowledge of those skilled in the art, as long as they do not deviate from the spirit of the present invention, also fall within the scope of the present invention.

[0014] [Polymer] The polymer obtained by the production method of the present invention contains a structural unit having a phenolic hydroxyl group, a structural unit having an acid-dissociable group, and a structural unit having a photoacid-generating group. Each structural unit constituting the polymer will be described below.

[0015] (Structural Unit Having a Phenolic Hydroxyl Group) The structural unit having a phenolic hydroxyl group is specifically a structure represented by the following general formula (1-0): [In general formula (1-0), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １２ represents a single bond or a divalent linking group which may have a hetero atom, and n represents an integer of 1 to 3. In formula (1-0), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, and is more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom, from the viewpoint of industrial availability.

[0016] In the formula (1-0), R １２ R is a divalent linking group which may have a heteroatom, or a single bond. １２ In the formula (I), preferred examples of the divalent linking group containing a hetero atom include *-O-, *-C(=O)-O-, *-C(=O)-, *-O-C(=O)-O-, *-C(=O)-NH-, *-NH-, *-NH-C(=NH)- (H may be substituted with a substituent such as an alkyl group or an acyl group), *-S-, and *-S(=O) ２-, *-S(=O) ２ -O-, general formula *-Y ２１ -O-Y ２２ -, *-Y ２１ -O-, *-Y ２１ -C(=O)-O-, *-C(=O)-O-Y ２１ -, *-[Y ２１ -C(=O)-O] ｍ” -Y ２２ -, *-Y21-OC(=O)-Y ２２ - or *-Y ２１ -S(=O) ２ -O-Y ２２ -, wherein Y ２１ and Y ２２ are each independently a divalent hydrocarbon group which may have a substituent, O is an oxygen atom, and m" is an integer of 0 to 3. * represents a bond to the main chain. When the divalent linking group containing a hetero atom is *-C(=O)-NH-, *-C(=O)-NH-C(=O)-, *-NH-, or *-NH-C(=NH)-, the H may be substituted with a substituent such as an alkyl group or acyl. The substituent (alkyl group, acyl group, etc.) preferably has 1 to 10 carbon atoms, more preferably 1 to 8, and particularly preferably 1 to 5. General formula *-Y ２１ -O-Y ２２ -, *-Y ２１ -O-, *-Y ２１ -C(=O)-O-, *-C(=O)-O-Y ２１ -, *-[Y ２１ -C(=O)-O] ｍ” -Y ２２ -, *-Y ２１ -OC(=O)-Y ２２ - or *-Y ２１ -S(=O) ２ -O-Y ２２ -Middle, Y ２１ and Y ２２ are each independently a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include R ２３ Examples of the divalent hydrocarbon group include the same groups as those mentioned in the description of the divalent hydrocarbon group in Y. ２１As Y, a linear aliphatic hydrocarbon group is preferred, a linear alkylene group is more preferred, a linear alkylene group having 1 to 5 carbon atoms is even more preferred, and a methylene group or an ethylene group is particularly preferred. ２２ is preferably a linear or branched aliphatic hydrocarbon group, more preferably a methylene group, an ethylene group or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group. ２１ -C(=O)-O] ｍ” -Y ２２ In the group represented by -, m" is an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 1. That is, the group represented by the formula *-[Y ２１ -C(=O)-O] ｍ” -Y ２２ The group represented by - includes the group represented by the formula *-Y ２１ -C(=O)-O-Y ２２ Among them, groups represented by the formula *-(CH2) are particularly preferred. ａ’ -C(=O)-O-(CH ２ ) ｂ’ In the formula, a' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1. b' is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, even more preferably 1 or 2, and most preferably 1.

[0017] R １２ is preferably a single bond, an ester bond [*-C(=O)-O-], an ether bond (*-O-), a linear or branched alkylene group, or a combination thereof, more preferably a single bond or an ester bond, and even more preferably a single bond.

[0018] In the present invention, polymerization is carried out using a monomer having a structure in which the phenolic hydroxyl group is protected with an acetal group as a monomer that provides a structural unit having a phenolic hydroxyl group. Specifically, a monomer having a structure in which the phenolic hydroxyl group of a compound represented by the following general formula (1) is protected with an acetal group represented by the following general formula (1-1) can be mentioned. [In general formula (1), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １２ is a single bond or a divalent linking group which may have a hetero atom. n is an integer of 1 to 3. In general formula (1-1), R １３ and R １４ are each independently a hydrogen atom or an alkyl group. １５ is a hydrocarbon group. １５ is R １３ or R １４ may bond to any one of the following to form a ring. * represents a bond to the oxygen atom in formula (1).

[0019] R in general formula (1) １１ , R １２ and n are the same as in formula (1-0).

[0020] Examples of the acetal group include a group represented by the following general formula (1-1).

[0021] In the formula (1-1), R １３ and R １４ are each independently a hydrogen atom or an alkyl group. １３ or R １４ Preferably, either one of R is an alkyl group having 1 to 5 carbon atoms. Specific examples of preferred alkyl groups include linear or branched alkyl groups. More specific examples include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, and neopentyl groups. Methyl or ethyl groups are more preferred, and methyl groups are particularly preferred. In addition, R １３ or R １４When either of R is an alkyl group, the other is preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom. １５ is a hydrocarbon group. １５ is R １３ or R １４ * represents a bond to the oxygen atom of formula (1).

[0022] In the formula (1-1), R １５ Examples of the hydrocarbon group include a linear or branched alkyl group and a cyclic hydrocarbon group. The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and the like. Among these, a methyl group, an ethyl group, or an n-butyl group is preferred, a methyl group or an ethyl group is more preferred, and an ethyl group is even more preferred.

[0023] The branched alkyl group preferably has 3 to 10 carbon atoms, more preferably 3 to 5. Specific examples include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group, with an isopropyl group being preferred.

[0024] R １５ When is a cyclic hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and may be a polycyclic group or a monocyclic group. As an aliphatic hydrocarbon group that is a monocyclic group, a group in which one hydrogen atom has been removed from a monocycloalkane is preferred. As the monocycloalkane, one having 3 to 6 carbon atoms is preferred, and specific examples thereof include cyclopentane and cyclohexane. As an aliphatic hydrocarbon group that is a polycyclic group, a group in which one hydrogen atom has been removed from a polycycloalkane is preferred, and as the polycycloalkane, one having 7 to 12 carbon atoms is preferred, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, etc.

[0025] R １５ When R is an aromatic hydrocarbon group, it preferably has 5 to 30 carbon atoms, more preferably 5 to 20, even more preferably 6 to 15, and particularly preferably 6 to 12. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which some of the carbon atoms constituting the aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in aromatic heterocycles include oxygen atoms, sulfur atoms, and nitrogen atoms. Specific examples of aromatic heterocycles include pyridine rings and thiophene rings. １５ Specific examples of the aromatic hydrocarbon group in the formula (I) include a group in which one hydrogen atom has been removed from the aromatic hydrocarbon ring or aromatic heterocycle (an aryl group or a heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound containing two or more aromatic rings (e.g., biphenyl, fluorene, etc.); and a group in which one hydrogen atom of the aromatic hydrocarbon ring or aromatic heterocycle has been substituted with an alkylene group (e.g., an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocycle preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

[0026] R １５ The cyclic hydrocarbon group in may have a substituent. Examples of the substituent include -R Ｐ１ , -R Ｐ２ -O-R Ｐ１ , -R Ｐ２ -CO-R Ｐ１ , -R Ｐ２ -CO-OR Ｐ１ , -R Ｐ２ -O-CO-R Ｐ１ , -R Ｐ２ -OH, -R Ｐ２ -CN or -R Ｐ２ -COOH, etc. Ｐ１ R is a monovalent linear saturated hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms. Ｐ２is a single bond, a divalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms. Ｐ１ and R Ｐ２ Some or all of the hydrogen atoms in the chain saturated hydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, and the aromatic hydrocarbon group may be substituted with fluorine atoms. The aliphatic cyclic saturated hydrocarbon group may have one or more of one type of the above-mentioned substituents, or may have one or more of each of two or more types of the above-mentioned substituents. Examples of the monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group. Examples of monovalent aliphatic cyclic saturated hydrocarbon groups having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, and cyclododecyl; and polycyclic aliphatic saturated hydrocarbon groups such as bicyclo[2.2.2]octanyl, tricyclo[5.2.1.02,6]decanyl, tricyclo[3.3.1.13,7]decanyl, tetracyclo[6.2.1.13,6.02,7]dodecanyl, and adamantyl. Examples of monovalent aromatic hydrocarbon groups having 6 to 30 carbon atoms include groups in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene. R Ｐ２ In the formula (I), examples of the divalent linear saturated hydrocarbon group having 1 to 10 carbon atoms, the divalent alicyclic saturated hydrocarbon group having 3 to 20 carbon atoms, and the divalent aromatic hydrocarbon group having 6 to 30 carbon atoms include groups in which one hydrogen atom has been removed from each of the above-mentioned monovalent hydrocarbon groups.

[0027] Among the above, R １５ is preferably a linear or branched alkyl group, more preferably a linear alkyl group.

[0028] R １５ But, R １３ or R １４When the cyclic group is bonded to any one of the above to form a ring, the cyclic group is preferably a 4- to 7-membered ring, more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

[0029] In the formula (1), n ​​is an integer of 1 to 3, preferably 1 or 2, and more preferably 1.

[0030] Specific examples of monomers in which the phenolic hydroxyl group is protected with an acetal group are shown below. α represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.

[0031]

[0032] In the production method of the embodiment, the monomer that provides the structural unit having a phenolic hydroxyl group may be used alone or in combination of two or more. The monomer is preferably a monomer having a structure in which the phenolic hydroxyl group of the compound represented by general formula (1) is protected with an acetal group represented by general formula (1-1), because such a monomer has excellent workability and facilitates more stable synthesis of the polymer of the present invention.

[0033] (Structural Unit Having Acid-Dissociable Group) The polymer obtained by the production method of the present invention is produced using a monomer having an acid-dissociable group as one of the monomers. The term "acid-dissociable group" refers to a group in which at least a part of the bond in the structure of the acid-dissociable group can be cleaved by the action of an acid. The structural unit having an acid-dissociable group in the polymer changes the solubility of the polymer in a developer for photolithography by dissociating the acid-dissociable group by the action of an acid to generate a highly polar carboxyl group. As the monomer having an acid-dissociable group, a wide variety of conventionally known monomers can be used. Among them, monomers having an acid-dissociable group are preferred because they are likely to improve the properties (sensitivity, shape, etc.) in lithography using EUV (extreme ultraviolet) or EB (electron beam): [In general formula (2), R ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２２represents a single bond or a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a hetero atom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a hetero atom. ２３ represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a heteroatom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a heteroatom. m is an integer of 0 to 2. R ２４ is an acid-dissociable group represented by the following general formula (2-1): [In general formula (2-1), R ２４１ represents a carbon atom. ２４２ is R ２４１ * represents a bond to the oxygen atom in formula (2). ２４３ is an alkyl group or aromatic hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, or a group represented by the following general formula (2-1-1): In general formula (2-1-1), R ２４３１ , R ２４３２ and R ２４３３ are each independently a hydrogen atom or a saturated aliphatic hydrocarbon group. ２４３１ , R ２４３２ and R ２４３３ Two or more of the following may be bonded to each other to form a ring structure. * represents R in formula (2-1). ２４１ It means a bond to the group represented by the following formula.] is preferred.

[0034] In the formula (2), R ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２１ The alkyl group having 1 to 5 carbon atoms in R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. ２１The halogenated alkyl group having 1 to 5 carbon atoms in R is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms have been substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being particularly preferred. ２１ As the alkyl group, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms is preferred, and from the viewpoint of industrial availability, a hydrogen atom or a methyl group is more preferred, and a methyl group is even more preferred.

[0035] In the formula (2), R ２２ represents a single bond or a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a hetero atom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a hetero atom. ２２ The divalent hydrocarbon group and the heteroatom-containing group substituting part or all of the hydrogen atoms in the hydrocarbon group in ２３ Examples include those similar to those in

[0036] In the formula (2), R ２３ represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a heteroatom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a heteroatom. ２３The divalent hydrocarbon group in may be a chain hydrocarbon group, a cyclic hydrocarbon group, or a combination thereof. Examples of the chain hydrocarbon group include a linear alkylene group and a branched alkylene group. Examples of the cyclic hydrocarbon group include alicyclic groups such as cyclopentane, cyclohexane, norbornane, isobornane, adamantane, and tricyclodecane; aromatic ring groups such as benzene, naphthalene, fluorene, anthracene, phenanthrene, pyrene, and biphenyl, and fused ring groups thereof. Examples of substituents that the hydrocarbon group may have include an alkyl group, a cycloalkyl group, an alkoxy group, an acetyl group, a hydroxyl group, a cyano group, and a halogen atom. In addition, some of the carbon atoms contained in the hydrocarbon group may be replaced with a heteroatom or a group containing a heteroatom, thereby forming an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a heterocycle, or the like.

[0037] In the formula (2), m is an integer of 0 to 2, preferably 0 or 1, and more preferably 0. ２４ is an acid-dissociable group. ２４ The acid-dissociable group in the formula (2-1) is preferably an acid-dissociable group represented by the formula (2-1).

[0038] In the formula (2-1), R ２４１ represents a carbon atom. ２４２ is R ２４１ R is a group that forms an alicyclic ring or a condensed ring of an alicyclic ring and an aromatic ring together with R. ２４２ is R ２４１ The alicyclic hydrocarbon group formed together with may be monocyclic or polycyclic. As an alicyclic hydrocarbon group that is a monocyclic group, a group in which two hydrogen atoms have been removed from a monocycloalkane is preferred. The monocycloalkane is preferably one having 3 to 6 carbon atoms, specific examples of which include cyclopentane and cyclohexane. As an aliphatic hydrocarbon group that is a polycyclic group, a group in which two hydrogen atoms have been removed from a polycycloalkane is preferred, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, specific examples of which include adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, etc.

[0039] R ２４２ is R ２４１ The alicyclic portion of the condensed ring formed by the alicyclic ring and the aromatic ring together may be a monocyclic ring or a polycyclic ring. Specific examples of the aromatic hydrocarbon group portion of the condensed ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and aromatic heterocycles in which some of the carbon atoms constituting the aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in the aromatic heterocycle include oxygen atoms, sulfur atoms, and nitrogen atoms. Specific examples of aromatic heterocycles include pyridine rings, thiophene rings, and furan rings.

[0040] In the formula (2-1), R ２４２ is R ２４１ The alicyclic ring formed together with the aromatic ring or the condensed ring of the alicyclic ring and the aromatic ring may have a substituent, such as a methyl group, an ethyl group, a propyl group, a hydroxy group, a hydroxyalkyl group, a carboxy group, a halogen atom, an alkoxy group, an acyl group, an alkyloxycarbonyl group, or an alkylcarbonyloxy group.

[0041] In the formula (2-1), R ２４３ is an alkyl group or aromatic hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, or a group represented by the general formula (2-1-1) above.

[0042] R ２４３ Specific examples of the alkyl group having 1 to 10 carbon atoms in the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, a methyl group, an ethyl group, an n-butyl group, an isopropyl group, and a tert-butyl group are preferred, and a methyl group, an ethyl group, or an isopropyl group is more preferred.

[0043] R ２４３Examples of the substituent that the alkyl group having 1 to 10 carbon atoms may have include a hydroxyl group, a carboxyl group, a halogen atom, an alkoxy group, and an alkyloxycarbonyl group.

[0044] R ２４３ The aromatic hydrocarbon group in the formula (I) is a hydrocarbon group having at least one aromatic ring, and may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is preferably 5 to 30, more preferably 5 to 20, even more preferably 6 to 15, and particularly preferably 6 to 12. Specific examples include phenyl, naphthyl, anthracenyl, phenanthryl, and the like, as well as tolyl and benzyl groups in which these groups are substituted with alkyl groups (methyl, ethyl, propyl, etc.) or alkylene groups. Furthermore, aromatic heterocycles in which some of the carbon atoms constituting the aromatic ring are substituted with heteroatoms such as oxygen atoms, sulfur atoms, or nitrogen atoms may also be used, such as pyridyl, thienyl, and furanyl groups.

[0045] R ２４３ Examples of the substituent that the aromatic hydrocarbon group may have include a hydroxyl group, a carboxyl group, a halogen atom, an alkoxy group, and an alkyloxycarbonyl group.

[0046] In the formula (2-1-1), R ２４３１ , R ２４３２ and R ２４３３ are each independently a hydrogen atom or a saturated aliphatic hydrocarbon group. ２４３１ , R ２４３２ and R ２４３３ The saturated aliphatic hydrocarbon group in the formula (I) includes a chain saturated hydrocarbon group, an alicyclic saturated hydrocarbon group, or a combination thereof.

[0047] R ２４３１ , R ２４３２ and R ２４３３ The number of carbon atoms in the chain saturated hydrocarbon group in the formula (I) is preferably 1 to 10, and more preferably 1 to 5. Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.

[0048] R２４３１ , R ２４３２ and R ２４３３ The number of carbon atoms in the alicyclic saturated hydrocarbon group in the formula (I) is preferably 3 to 20, and examples of the alicyclic saturated hydrocarbon group include monocyclic groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group; and polycyclic groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo[3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7]dodecanyl group, and an adamantyl group.

[0049] The formula (2-1-1) (wherein R ２４３１ , R ２４３２ and R ２４３３ Two or more of R may be bonded to each other to form a ring structure. ２４３１ , R ２４３２ and R ２４３３ Examples of the group containing a carbon-carbon double bond formed by two or more of the above being bonded to each other to form a cyclic structure include a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, a methylcyclohexenyl group, a cyclopentylidene-ethenyl group, a cyclohexylidene-ethenyl group, etc. Among these, from the viewpoint of ease of synthesis of the monomer of general formula (2), a cyclopentenyl group, a cyclohexenyl group, and a cyclopentylidene-ethenyl group are preferred.

[0050] R ２４３１ , R ２４３２ and R ２４３３ Among these, from the viewpoint of ease of synthesis of the monomer of the general formula (2), is preferably a hydrogen atom or a monovalent chain saturated hydrocarbon group having 1 to 10 carbon atoms, and among these, a hydrogen atom, a methyl group, or an ethyl group is more preferred, and a hydrogen atom is particularly preferred.

[0051] Among the acid-dissociable groups represented by general formula (2-1), R ２４３An acid-dissociable group in which R is an aromatic hydrocarbon group or a group represented by general formula (2-1-1) is a group that can dissociate with relatively low energy and is suitable for improving the sensitivity of resists. The method of the present invention is suitable for polymerizing a polymer containing such easily decomposable acid-dissociable groups that dissociate with relatively low energy while suppressing decomposition of the structure. Specific examples of acid-dissociable groups represented by general formula (2-1) are shown below. * denotes a bond to the oxygen atom in formula (2).

[0052] Specific examples of the monomer of the general formula (2) include monomers having a structure in which an acid-dissociable group such as those exemplified in [Chemical Formula 14] to [Chemical Formula 20] is bonded to an ester bond of acrylic acid or methacrylic acid.

[0053] (Structural Unit Having a Photoacid Generating Group) The polymer obtained by the production method of the present invention is produced using a monomer having a photoacid generating group as one of the monomers. The photoacid generating group generates an acid when irradiated with high-energy rays such as ultraviolet rays, far ultraviolet rays, electron beams, EUV, X-rays, gamma rays, and synchrotron radiation. When a polymer compound having this structure is used as the base resin of a resist composition, it is possible to appropriately control the movement and diffusion of the generated acid. A wide variety of conventionally known monomers having a photoacid generating group can be used, but particularly preferred are those having a structure represented by the following general formula (3): [In general formula (3), R ３１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ３２ is a single bond or an aromatic hydrocarbon group which may have a substituent. k is 0 or 1. R ３３ represents a single bond or a hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３４ represents a hydrocarbon group having 1 to 15 carbon atoms, and some or all of the hydrogen atoms in the hydrocarbon group may be replaced by fluorine atoms.３５ , R ３６ and R ３７ each independently represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３５ , R ３６ and R ３７ any two or more of which may be bonded to each other to form a ring together with the sulfur atom in formula (3).] is preferred.

[0054] In the formula (3), R ３１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ３１ The alkyl group having 1 to 5 carbon atoms in R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. ３１ The halogenated alkyl group having 1 to 5 carbon atoms in R is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms have been substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom being particularly preferred. ３１ As the alkyl group, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms is preferred, and from the viewpoint of industrial availability, a hydrogen atom or a methyl group is more preferred, and a methyl group is even more preferred.

[0055] R in the above general formula (3) ３２ is a single bond or an aromatic hydrocarbon group which may have a substituent. Examples of the aromatic hydrocarbon group include groups in which two hydrogen atoms have been removed from an aromatic ring such as benzene, naphthalene, anthracene, pyrene, or biphenyl, and a phenylene group is preferred. Examples of the substituent include an alkyl group, a cycloalkyl group, an alkoxy group, an acetyl group, a hydroxyl group, a cyano group, and a halogen atom, and the substituent is preferably unsubstituted. R in the above general formula (3) ３３represents a hydrocarbon group having 1 to 30 carbon atoms, which may have a single bond or a substituent, and some of the carbon atoms in the hydrocarbon group may be replaced with a heteroatom or a group containing a heteroatom. The hydrocarbon group may be a chain hydrocarbon group, a cyclic hydrocarbon group, or a combination thereof. Examples of the chain hydrocarbon group include linear alkylene groups and branched alkylene groups. Examples of the cyclic hydrocarbon group include alicyclic groups such as cyclopentane, cyclohexane, norbornane, adamantane, and tricyclodecane; aromatic groups such as benzene, naphthalene, anthracene, pyrene, and biphenyl; and fused ring groups thereof. Examples of the substituent that the hydrocarbon group may have include alkyl groups, cycloalkyl groups, alkoxy groups, acetyl groups, hydroxyl groups, cyano groups, and halogen atoms. In particular, fluorine atoms and iodine atoms exhibit high absorbance at 13.5 nm EUV and are therefore effective in increasing the sensitivity of EUV lithography. In addition, some of the carbon atoms contained in the hydrocarbon group may be replaced with heteroatoms or groups containing heteroatoms, thereby forming an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, or the like. ３４ represents a hydrocarbon group having 1 to 15 carbon atoms, in which some or all of the hydrogen atoms may be substituted with fluorine atoms. The hydrocarbon group is a chain hydrocarbon group, a cyclic hydrocarbon group, or a group combining these, preferably a chain saturated hydrocarbon group or a cyclic saturated hydrocarbon group, more preferably a chain saturated hydrocarbon group, and even more preferably a chain saturated hydrocarbon group in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0056] Preferred anion structures of the sulfonium salt of the monomer represented by the above general formula (3) include, but are not limited to, those shown below.

[0057] In the above general formula (3), R ３５ , R ３６ and R ３７each independently represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced by a heteroatom or a group containing a heteroatom. Examples of the hydrocarbon group include aromatic hydrocarbon groups such as a phenyl group, a naphthyl group, an anthracenyl group, and a biphenyl group; alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a tert-butyl group; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, a norbornyl group, a tricyclo[5.2.1.02,6]decanyl group, and an adamantyl group, or a group combining these. ３５ , R ３６ and R ３７ Any two or more of the R may be bonded to each other to form a ring together with the sulfur atom in formula (3). ３５ , R ３６ , and R ３７ The sulfonium cation containing the formula (I) preferably contains an aromatic hydrocarbon group. Substituents that the hydrocarbon group may have include a hydroxyl group, a cyano group, a halogen atom, and the like, with a hydroxyl group and a fluorine atom being preferred. Furthermore, some of the carbon atoms contained in the hydrocarbon group may be replaced with a heteroatom or a group containing a heteroatom, and may form a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, a lactone ring, a sultone ring, a carboxylic acid anhydride, a haloalkyl group, or the like.

[0058] Specific examples of the sulfonium cation structure represented by the general formula (3) include those shown below, although the present invention is not limited thereto.

[0059] Specific structures of the monomer of the present invention represented by the above general formula (3) include any combination of anions and cations of the structures exemplified above.

[0060] Here, a method for synthesizing a salt that can be used as a raw material for the monomer represented by the above general formula (3) will be described. The following sulfonium cations will be used as examples, but the present invention is not limited to this method. (wherein M represents a cation. R ４１ , R ４２ , R ４３ , R ４４ represents a monovalent organic group. ３１ , R ３２ , k, R ３３ , R ３４ , R ３５ , R ３６ , R ３７ is the same as above. X － indicates a halide ion or a methyl sulfate ion.)

[0061] First, the sulfonate salt represented by the above formula (20) is synthesized with reference to JP 2010-215608 A. Next, the cation of the obtained sulfonate salt is exchanged with an ammonium cation by ion exchange to obtain the ammonium sulfonate salt represented by the above formula (21). In this case, the ion exchange reaction can be carried out using an organic solvent such as dichloromethane, ethyl acetate, methyl isobutyl ketone, methanol, ethanol, or acetonitrile, either alone or in combination with water. For example, a mixture with an aqueous solution of benzyltrimethylammonium chloride can be used.

[0062] Next, the resulting ammonium sulfonate salt is reacted with an acylating agent to synthesize the acylated ammonium sulfonate salt represented by formula (22). This reaction can be easily carried out by a known method. For example, there is a method in which the ammonium sulfonate salt represented by formula (21) is reacted with an acylating agent and a base such as triethylamine, pyridine, or 4-dimethylaminopyridine in a solvent such as methylene chloride, toluene, hexane, diethyl ether, tetrahydrofuran, or acetonitrile, either sequentially or simultaneously, and then cooled or heated as necessary to carry out the reaction.

[0063] Furthermore, the sulfonium salt represented by the above formula (23) is synthesized from the obtained acylated ammonium sulfonate salt represented by the above formula (22). For example, the reaction can be carried out by mixing an organic solvent such as dichloromethane, ethyl acetate, methyl isobutyl ketone, methanol, ethanol, or acetonitrile, either alone or in combination with water, with an aqueous solution of triphenylsulfonium chloride.

[0064] [Method for Producing Polymer] The method for producing a polymer of the present invention includes a polymerization step and a deprotection step, and may further include a purification step. Each step of the method for producing a polymer of the present invention will be described below.

[0065] [Polymerization Step] The method for producing a polymer of the present invention includes a step of polymerizing, in a solvent, a monomer in which a phenolic hydroxyl group is protected with an acetal group, a monomer having an acid-dissociable group, and a monomer having a photoacid-generating group. The mode of the polymerization reaction is not particularly limited, and conventionally known polymerization methods such as radical polymerization, cationic polymerization, and living anionic polymerization can be applied.

[0066] In the case of radical polymerization, the monomer, radical polymerization initiator, and optionally, chain transfer agent are dissolved in a solvent and heated and stirred, preferably under an inert gas atmosphere such as nitrogen. For example, the polymerization can be carried out by a so-called bulk polymerization method in which all raw materials, such as the monomer, polymerization initiator, and chain transfer agent, are dissolved in a solvent and heated to the polymerization temperature; a method in which the monomer is dissolved in a solvent and heated to the polymerization temperature, followed by the addition of the polymerization initiator; or a so-called dropwise polymerization method in which a solution of the monomer, polymerization initiator, and other components dissolved in a solvent is added dropwise to a solvent heated to the polymerization temperature. Among these, the dropwise polymerization method is preferred because of its high reproducibility for each production lot. In particular, a so-called independent dropwise method in which the monomer and the polymerization initiator, which is a radical generating source, are added dropwise separately can also be carried out. It is also possible to previously supply a portion of each of the monomer, polymerization initiator, chain transfer agent, and other components to the polymerization system. In the dropping method, the monomer concentration and radical concentration in the polymerization system can be adjusted by changing the composition of the monomer solution to be supplied and the supply speed of the monomer solution and polymerization initiator, thereby controlling the dispersity and composition distribution of the produced polymer.

[0067] The radical polymerization initiator may be a conventionally known one, such as an azo polymerization initiator or a peroxide polymerization initiator. Specific examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 1,1'-azobis(cyclohexane-1-carbonitrile), and 4,4'-azobis(4-cyanovaleric acid). Azo compound polymerization initiators are preferred because of their excellent handling safety. Specific examples of peroxide-based polymerization initiators include decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis(3,5,5-trimethylhexanoyl) peroxide, succinic acid peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxypivalate, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate. These polymerization initiators can be used alone or in combination. The amount of polymerization initiator used can be selected depending on the target molecular weight, the types of monomers, polymerization initiators, chain transfer agents, solvents, etc., the structural unit composition, the polymerization temperature, the dropping rate, and the like.

[0068] Known chain transfer agents can be used as needed. Thiol compounds are preferred, and a wide variety of known thiol compounds can be selected. Specific examples include t-dodecyl mercaptan, mercaptoethanol, mercaptoacetic acid, and mercaptopropionic acid. Thiol compounds having a structure in which a 2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl group is bonded to a saturated aliphatic hydrocarbon are particularly preferred because they are effective in suppressing roughness and defects in lithography patterns. The amount of chain transfer agent used can be selected depending on the target molecular weight, the types of monomers, polymerization initiators, chain transfer agents, and solvents, the structural unit composition, the polymerization temperature, the dropping rate, and other factors.

[0069] The solvent used in the polymerization reaction is not particularly limited as long as it can stably dissolve the monomers, polymerization initiator, chain transfer agent, and the resulting polymer. Specific examples of the polymerization solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, and methyl propionate; ether esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as tetrahydrofuran, 1,4-dioxane, and ethylene glycol dimethyl ether; aromatic hydrocarbons such as toluene and xylene; N,N-dimethylformamide, acetonitrile, and chloroform. In the polymerization step, the polymerization solvent may contain a compound serving as a proton source, and the content thereof is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, of the total solvent. If the content of the compound serving as a proton source is within the above-mentioned numerical range, deprotection and dissociation of the acid-dissociable group are less likely to occur during the polymerization, resulting in good deprotection results, as described below. Specific examples of the compound serving as a proton source include the compounds serving as proton sources described in the deprotection step, which will be described below.

[0070] These polymerization solvents may be used alone or in combination of two or more. Also, a high-boiling compound that has high solubility for the monomers, polymerization initiator, chain transfer agent, and the resulting polymer, such as 3-methoxy-3-methyl-1-butyl acetate, ethyl 3-ethoxypropionate, γ-butyrolactone, diethylene glycol dimethyl ether, N-methylpyrrolidone, or dimethyl sulfoxide, may be used in combination.

[0071] There is no particular restriction on the amount of the polymerization solvent used, but if the amount of the solvent used is too small, the monomer may precipitate or the viscosity may become too high, making it impossible to maintain a uniform polymerization system, while if the amount of the solvent used is too large, the conversion rate of the monomer may be insufficient or the molecular weight of the polymer may not be increased to the desired value. Usually, the amount of the solvent used is 0.5 to 20 parts by mass, preferably 1 to 10 parts by mass, per part by mass of the monomer.

[0072] In the dropping polymerization method, the amount of solvent charged in advance into the reaction vessel (hereinafter sometimes referred to as the "initially charged solvent") may be at least the minimum amount that allows stirring, but if it is more than necessary, the amount of monomer solution that can be supplied decreases, which is undesirable because it reduces production efficiency. Typically, the volume ratio of the solvent to the final charge amount (i.e., the total amount of the initially charged solvent and the monomer solution and initiator solution to be dropped) is selected, for example, from a range of 1 / 30 or more, preferably 1 / 20 to 1 / 2, and particularly preferably 1 / 10 to 1 / 3. Note that a portion of the monomer may be premixed with the initially charged solvent.

[0073] In the dropping polymerization method, a short dropping time is undesirable because the degree of dispersion tends to become broad and the temperature of the polymerization solution decreases due to the large amount of solution being dropped at once. Conversely, a long dropping time is undesirable because the polymer is subjected to more heat than necessary and productivity decreases. Therefore, the dropping time is usually selected from the range of 0.5 to 24 hours, preferably 1 to 12 hours, and particularly preferably 2 to 8 hours.

[0074] After the dropwise addition is completed and after the temperature is raised to the polymerization temperature in the batch temperature-raising method, it is preferable to maintain the temperature for a certain period of time or further raise the temperature to carry out aging, thereby reacting the remaining unreacted monomer. If the aging time is too long, the production efficiency per unit time decreases and the polymer is subjected to more heat than necessary, which is undesirable. Therefore, the aging time is usually selected within 12 hours, preferably within 6 hours, and particularly preferably within the range of 1 to 4 hours.

[0075] The polymerization temperature can be appropriately selected depending on the boiling points of the solvent, monomer, chain transfer agent, etc., the half-life temperature of the polymerization initiator, etc. At low temperatures, polymerization proceeds slowly, resulting in productivity problems, while temperatures higher than necessary result in problems with the stability of the monomers and polymer. Therefore, the polymerization temperature is preferably selected within the range of 40 to 160°C, and particularly preferably 60 to 120°C. The polymerization temperature significantly affects the molecular weight and copolymer composition of the polymer, and therefore must be precisely controlled. Meanwhile, polymerization reactions are generally exothermic, and the polymerization temperature tends to increase, making it difficult to control at a constant temperature. For this reason, in the present invention, it is preferable to include at least one compound having a boiling point close to the target polymerization temperature as the polymerization solvent, and to set the polymerization temperature at or above the initial boiling point of the compound at the polymerization pressure. This method allows the latent heat of vaporization of the polymerization solvent to suppress an increase in polymerization temperature.

[0076] The polymerization pressure is not particularly limited and may be normal pressure, elevated pressure, or reduced pressure, but is usually normal pressure. In the case of radical polymerization, when radicals are generated from the initiator, nitrogen gas is generated in the case of an azo-based initiator, and oxygen gas is generated in the case of a peroxide-based initiator. Therefore, in order to suppress fluctuations in the polymerization pressure, it is preferable to use an open polymerization system and carry out the polymerization at near atmospheric pressure.

[0077] The decomposition rate of the acid-dissociable group in the polymerization step is １ The rate of decomposition of an acid-dissociable group in the polymerization step can be measured by the integral ratio of signals in H-NMR. The rate of decomposition of an acid-dissociable group in the polymerization step refers to the molar ratio of the structural units in which an acid-dissociable group has been dissociated from the structural units having an acid-dissociable group to the sum of the structural units in which an acid-dissociable group has been dissociated from the structural units having an acid-dissociable group and the structural units in which an acid-dissociable group has not been dissociated from the structural units having an acid-dissociable group, in the polymer after the polymerization step. Specifically, ２４ The structural unit from which the group is dissociated and the structural unit having an acid-dissociable group are represented by R ２４ The structural unit having an acid-dissociable group is selected from the structural units having an acid-dissociable group and the structural units having an acid-dissociable group in the general formula (2) R ２４ The molar ratio of structural units from which the group dissociates.

[0078] [Deprotection Step] The production method of the present invention includes a step of deprotecting the acetal groups at a specific ratio by contacting the polymer obtained in the polymerization step with a compound that serves as a proton source in the absence of an acid having a pKa of 8 or less. In the deprotection step of the present invention, it is important that the acetal groups that protect the phenolic hydroxyl groups are deprotected at a specific ratio while the acid-dissociable groups are not dissociated.

[0079] The temperature for the deprotection reaction is in the range of 0 to 120°C, preferably in the range of 20 to 100°C. If the reaction temperature is higher than this range, undesirable side reactions such as elimination of the acid-dissociable group and reaction of the eliminated acid-dissociable group with the phenolic hydroxyl group of p-hydroxystyrene occur. Furthermore, if the reaction temperature is lower than this range, the deprotection reaction takes a long time, resulting in reduced productivity, which is undesirable. The deprotection of a specific proportion of acetal groups in the present invention can be achieved by adjusting the temperature or time for the deprotection reaction depending on the monomer and the compound serving as the proton source.

[0080] The solvent used in the deprotection reaction is not particularly limited as long as it can stably dissolve the polymer before and after deprotection. Specific examples of the solvent include those similar to the polymerization solvent. These can be used alone or in combination of two or more.

[0081] (Compound serving as a proton source) In the production method of the present invention, a compound serving as a proton source is used in the step of deprotecting the acetal group. The compound serving as a proton source preferably contains at least one of alcohols and phenols, and more preferably an alcohol having 6 or fewer carbon atoms. Examples of alcohols having 6 or fewer carbon atoms include methanol, ethanol, propanol, isopropanol, butanol, sec-butanol, tert-butanol, amyl alcohol, hexanol, cyclohexanol, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0082] (Acids with a pKa of 8 or less) In the production method of the present invention, acids with a pKa of 8 or less are not used in the step of deprotecting the acetal group. Examples of acids with a pKa of 8 or less include acetic acid, oxalic acid, formic acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, malonic acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrobromic acid. Unless otherwise specified, the pKa of these acids is the value in water at 25°C. These values ​​can be known by referring to known literature (for example, "Chemical Handbook" edited by the Chemical Society of Japan, Maruzen Publishing).

[0083] The deprotection rate of the acetal group in the deprotection step is 98 mol% or less, preferably 97 mol% or less, and more preferably 95 mol% or less. The deprotection rate of the acetal group is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more. When the deprotection rate of the acetal group is within the above-mentioned range, the decomposition of the acid-dissociable group is reduced, and a high-purity polymer can be obtained. The deprotection rate can be kept within the above-mentioned range by adjusting the reaction temperature and reaction time of the deprotection reaction. The deprotection rate of the acid-dissociable group in the deprotection step is １ The deprotection rate can be measured by the integral ratio of the signals in H-NMR. １３ The deprotection rate in the deprotection step can be measured by the integral ratio of signals in C-NMR. The deprotection rate in the deprotection step refers to the molar ratio of structural units having a phenolic hydroxyl group from which an acetal group has been deprotected to the sum of structural units having a phenolic hydroxyl group protected with an acetal group and structural units having a phenolic hydroxyl group from which the acetal group has been deprotected, in the polymer after the deprotection step. Similarly, the acid-dissociable group decomposition rate in the deprotection step refers to the molar ratio of structural units from which an acid-dissociable group has been dissociated to the sum of structural units from which an acid-dissociable group has been dissociated and structural units from which an acid-dissociable group has not been dissociated, in the polymer after the deprotection step. Specifically, as in the "[polymerization step]", the deprotection rate in the deprotection step refers to the molar ratio of structural units from which an acid-dissociable group has been dissociated to R２４ The structural unit from which the group is dissociated and the structural unit having an acid-dissociable group are represented by R ２４ The structural unit having an acid-dissociable group is selected from the structural units having an acid-dissociable group and the structural units having an acid-dissociable group in the general formula (2) R ２４ The molar ratio of structural units from which the group dissociates.

[0084] [Purification Step] The production method of the present invention may further include a step of purifying the polymer obtained in the deprotection step using an alcohol-based solvent. When the polymer obtained by the production method of the present invention contains impurities such as solvent, unreacted monomer, oligomer, reaction by-product, etc., this step is effective for removing these impurities or for obtaining a polymer with a desired dispersity. The deprotection rate of the acetal groups in the polymer in the purification step is preferably more than 98 mol%, more preferably 99 mol% or more. When the deprotection rate of the acetal groups is within the above numerical range, the polymer can be used as a raw material for a high-quality resist material. The decomposition rate of the acid-dissociable groups in the purification step is １ Integral ratio of signals in H-NMR and １３ The deprotection rate can be measured by the integral ratio of the signals in C-NMR. １３ The deprotection rate in the purification step can be measured by the integral ratio of signals in C-NMR. The deprotection rate in the purification step refers to the molar ratio of structural units having a phenolic hydroxyl group from which an acetal group has been deprotected to the sum of structural units having a phenolic hydroxyl group protected with an acetal group and structural units having a phenolic hydroxyl group from which the acetal group has been deprotected, in the polymer after the purification step. Similarly, the acid-dissociable group decomposition rate in the purification step refers to the molar ratio of structural units from which an acid-dissociable group has been dissociated to the sum of structural units from which an acid-dissociable group has been dissociated and structural units from which an acid-dissociable group has not been dissociated, in the polymer after the purification step. Specifically, as in the "[polymerization step]", the deprotection rate in the purification step refers to the molar ratio of structural units from which an acid-dissociable group has been dissociated to R ２４ The structural unit from which the group is dissociated and the structural unit having an acid-dissociable group are represented by R ２４The structural unit having an acid-dissociable group is selected from the structural units having an acid-dissociable group and the structural units having an acid-dissociable group in the general formula (2) R ２４ The molar ratio of structural units from which the group dissociates.

[0085] Specifically, the method is carried out by diluting a solution containing a polymer by adding a good solvent as necessary, and then bringing the solution into contact with a poor solvent to precipitate the polymer and extract impurities into the liquid phase (hereinafter referred to as precipitation purification), or by extracting the polymer into a liquid-liquid two-phase solution, and extracting the polymer into the good solvent phase and the impurities into the poor solvent phase.

[0086] In the precipitation purification, the precipitated solid may be subjected to solid-liquid separation by a method such as filtration or decantation, and then the solid may be further washed with a poor solvent, etc. The purification may be carried out before or after the deprotection reaction.

[0087] The types and amounts of the poor solvent and good solvent used for purification are not particularly limited as long as they allow the polymer to be separated from low-molecular-weight compounds, and can be appropriately selected depending on the solubility of the polymer in the poor solvent, the type and amount of the solvent used in the polymerization, the type and amount of impurities, etc.

[0088] The temperature during purification must be strictly controlled because it significantly affects the molecular weight and dispersity of the polymer, and the removal rate of impurities such as residual monomers and initiator residues. If the purification temperature is too low, the solubility of impurities in the precipitation extraction treatment solvent and washing solvent will be insufficient, and impurities will not be sufficiently removed, resulting in inefficiency. Conversely, if the purification temperature is too high, the polymer will dissolve in the purification solvent, disrupting the composition balance in the low molecular weight region of the polymer and reducing the yield, which is undesirable. For this reason, purification is preferably carried out in the range of 0 to 80°C, preferably 0 to 60°C.

[0089] [Other Steps] After the purification step, the polymer may be subjected to filtration or solvent substitution, if necessary.

[0090] [Resist Resin Composition] The polymer obtained by the production method of the present invention is useful as a base polymer for a resist resin composition. In addition to the polymer, the resist resin composition contains an acid generator, an acid diffusion inhibitor, and a solvent capable of uniformly dissolving these components. Conventional known compounds can be used as these components. Furthermore, the resist composition can contain, as needed, conventional resist additives, such as organic carboxylic acids or phosphorus oxoacids for preventing deterioration of the acid generator's sensitivity and improving the resist pattern shape and deposition stability, additional resins for improving the performance of the resist film, surfactants for improving coatability, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, and dyes.

[0091] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

[0092] The acid-labile group decomposition rate and acetal group deprotection rate of the polymers synthesized in the examples are as follows: １ H-NMR and １３ Analysis was performed by C-NMR. Apparatus: Bruker AV500 Deuterated solvent: DMSO-d6 1H-NMR: Measurement temperature 30°C 13C-NMR: Measurement temperature 45°C, inverse gated decoupling method, chromium (III) acetylacetonate used

[0093] The monomers and solvents used in this example and their abbreviations are as follows: *1 PHS-EE: p-(1-ethoxyethoxy)styrene PHS: p-hydroxystyrene VCPMA: 1-vinylcyclopentyl methacrylate PCHMA: 1-phenylcyclohexyl methacrylate PCPMA: 1-phenylcyclopentyl methacrylate MCPMA: 1-methylcyclopentyl methacrylate Monomer A: triphenylsulfonium 3-(methacryloyloxy)-1-propanesulfonate *2 MEK: methyl ethyl ketone PGME: propylene glycol monomethyl ether

[0094] Example 1 (Polymerization Step) 14.0 g of PHS-EE, 21.9 g of VCPMA, and 23.1 g of Monomer A, each representing a monomer with a phenolic hydroxyl group protected by an acetal group, a monomer having an acid-dissociable group, and a monomer having a photoacid-generating group, were mixed in a vessel with 3.9 g of dimethyl 2,2'-azobis(2-methylpropionate), and 115.6 g of MEK to prepare a monomer solution. (The molar ratio of PHS-EE / VCPMA / Monomer A was 30 / 50 / 20.) 56.4 g of MEK was charged into a four-neck glass flask reaction vessel equipped with a thermometer, a condenser, and a stirrer. After creating a nitrogen atmosphere, the vessel was heated to 79°C. The monomer solution was added dropwise at a constant rate over 4 hours, and the polymerization reaction was continued for another 2 hours. After completion of the polymerization, the vessel was cooled to room temperature. Stirring during polymerization was carried out at 400 rpm using a PTFE football-shaped stirrer (Φ15 x 35 mm) and a magnetic stirrer (Tokyo Glass Instruments Co., Ltd., powerful stirrer F-205D). The composition ratio (molar ratio) of each structural unit in the polymer was calculated by NMR analysis. No signals derived from methacrylic acid units, which indicate decomposition of VCPMA units, were observed, and the decomposition rate of acid-dissociable groups was 0%. The polymerization conditions in the polymerization process, the decomposition rate of acid-dissociable groups, and whether or not the polymer precipitated are summarized in Table 1.

[0095] (Acetal Group Deprotection Step) 100 g of the polymerization solution obtained in the polymerization step and 15 g of methanol as a proton source were placed in a reaction vessel equipped with a thermometer, a condenser, and a stirrer, and the mixture was heated at 60°C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature. A portion of the reaction solution was sampled, and the solvent was distilled off under a nitrogen stream. NMR analysis showed that the deprotection rate of PHS-EE units was 90 mol %, and the decomposition rate of VCPMA units was 1 mol %. (Note that the decomposition rate of VCPMA units includes the decomposition of unreacted VCPMA monomers.) The reaction conditions, acetal group deprotection rate, and acid-dissociable group decomposition rate in the deprotection step are summarized in Table 2.

[0096] (Purification Step) The reaction solution obtained in the deprotection step was mixed with hexane and stirred to precipitate the polymer. After standing, the polymer was separated by decantation. The polymer was redissolved in an acetone / methanol mixed solvent (acetone / methanol weight ratio = 80 / 20), reprecipitated with hexane, and separated by decantation. This procedure was repeated four times, and finally the polymer was dissolved in an acetone / methanol mixed solvent. A portion of the purified polymer solution was sampled and dried under reduced pressure at 40°C to obtain a polymer powder, which was subjected to NMR analysis. The NMR analysis showed that the deprotection rate of PHS-EE was 100 mol %, and the decomposition rate of VCPMA was 0.1 mol %. At first glance, the acid-dissociable group decomposition rate appears to be lower than that in the deprotection step; this is thought to be due to the removal of methacrylic acid resulting from the decomposition of unreacted VCPMA monomer by purification. The acetal group deprotection rate and acid-dissociable group decomposition rate after the purification step are summarized in Table 3.

[0097] Examples 2 to 7, Comparative Examples 3 to 5 Polymerization reactions, deprotection reactions, and purification were carried out in accordance with Example 1, except that the types of monomers, polymerization solvents, and deprotection reaction conditions were changed as shown in Tables 1 and 2. However, in the purification steps of Example 7 and Comparative Example 5, an acetone / methanol mixed solvent (acetone / methanol weight ratio = 40 / 60) was used to redissolve the resin. The results of whether stirring was performed in the polymerization step, and the acetal group deprotection rate and acid-dissociable group decomposition rate after each step are summarized in Tables 1 to 3, respectively.

[0098] Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, except that PHS without a protecting group (MEK solution containing 25% by mass of PHS with a purity of 99%) was used instead of PHS-EE, and PCPMA was used instead of VCPMA. Since a deprotection step was not required, purification was carried out after the polymerization step in the same manner as in Example 1. The results of whether stirring was performed during the polymerization step and the acid-dissociable group decomposition rate after each step are summarized in Tables 1 to 3, respectively.

[0099] Comparative Example 2 Polymerization was carried out in the same manner as in Example 1, except that PHS not having a protecting group (MEK solution containing 25% by mass of PHS with a purity of 99%) was used instead of PHS-EE. A large amount of polymer precipitated during the polymerization reaction, making stirring impossible and the polymerization reaction could not be continued.

[0100]

[0101]

[0102]

[0103] In Examples 1 to 7 using the method of the present invention, the acetal protecting groups of p-hydroxystyrene were deprotected at 63 to 90 mol% without using an acid catalyst in the deprotection step, and 98 mol% or more of deprotection was achieved in the subsequent purification step, while decomposition of the acid-labile groups was also suppressed to a low level. In particular, even in Examples 1 to 6, in which a monomer having a readily decomposable acid-labile group was used, a post-purification acid-labile group decomposition rate of less than 1 mol% was achieved. In Example 4, it was found that even if the polymerization solvent contained a proton source (propylene glycol monomethyl ether), deprotection results comparable to those of the other Examples were obtained as long as the proton source was 20 mass% or less of the total polymerization solvent. On the other hand, in Comparative Example 1, in which p-hydroxystyrene in which the phenolic hydroxyl group was not protected was polymerized, decomposition of the readily decomposable acid-labile group was observed. This is thought to be due to the weak acidity of the phenolic hydroxyl group, which partially decomposed the acid-labile group. Furthermore, in Comparative Example 2, in which p-hydroxystyrene was polymerized with a monomer having a readily decomposable acid-labile group different from that in Comparative Example 1, a large amount of polymer precipitated during polymerization, making stirring impossible. Furthermore, in Comparative Example 3, in which the acetal groups were deprotected using an acid catalyst (p-toluenesulfonic acid), the decomposition rate of the readily decomposable acid-dissociable groups was high. In Comparative Example 4, in which all acetal groups were deprotected in the deprotection step, the decomposition rate of the readily decomposable acid-dissociable groups was high. Although the reason for this is unclear, it is speculated that the deprotection reaction of the acetal groups proceeds more preferentially than the decomposition of the acid-dissociable groups, and that the decomposition of the acid-dissociable groups begins after the deprotection reaction of the acetal groups is completed. In Comparative Example 5, in which the deprotection reaction was not performed and only purification was carried out after polymerization, the deprotection rate of the acetal groups was insufficient.

[0104] According to the present invention, in the production of a polymer containing a structural unit having a phenolic hydroxyl group, a structural unit having an easily decomposable acid-dissociable group, and a structural unit having a photoacid-generating group, it is possible to suppress the generation of a carboxylic acid structural unit due to decomposition of the easily decomposable acid-dissociable group, and to produce a high-purity polymer. The polymer obtained by the present invention can be suitably used in a resist for EUV or EB lithography.

Claims

1. A method for producing a polymer containing a structural unit having a phenolic hydroxyl group, a structural unit having an acid-dissociable group, and a structural unit having a photoacid-generating group, the method comprising the steps of: polymerizing, in a solvent, a monomer having a structure in which the phenolic hydroxyl group is protected with at least an acetal group, a monomer having an acid-dissociable group, and a monomer having a photoacid-generating group; and a deprotection step in which the polymer obtained in the polymerization step is contacted with a compound that serves as a proton source in the absence of an acid having a pKa of 8 or less to deprotect the acetal groups, wherein the deprotection rate of the acetal groups is 98 mol % or less.

2. The method for producing a polymer according to claim 1, wherein the proton source in the deprotection step comprises at least one of an alcohol and a phenol.

3. The method for producing a polymer according to claim 2, wherein the alcohol has 6 or less carbon atoms.

4. The method for producing a polymer according to any one of claims 1 to 3, wherein the acid having a pKa of 8 or less is selected from the group consisting of acetic acid, oxalic acid, formic acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, malonic acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrobromic acid.

5. The method for producing a polymer according to any one of claims 1 to 4, wherein the deprotection rate of the acetal groups in the polymer in the deprotection step is 50 mol % or more.

6. The method for producing a polymer according to any one of claims 1 to 5, wherein the deprotection rate of the acetal groups in the polymer in the deprotection step is 95 mol % or less.

7. The method for producing a polymer according to any one of claims 1 to 6, further comprising a step of purifying the polymer obtained in the deprotection step using an alcohol-based solvent.

8. The method for producing a polymer according to claim 7, wherein the deprotection rate of the acetal groups in the polymer in the purification step is more than 98% by mole.

9. The method for producing a polymer according to any one of claims 1 to 8, wherein in the polymerization step, the content of the compound serving as a proton source contained in the polymerization solvent is 20 mass % or less of the total solvent.

10. The method for producing a polymer according to any one of claims 1 to 9, wherein the monomer having a structure in which a phenolic hydroxyl group is protected with an acetal group includes a monomer having a structure in which a phenolic hydroxyl group of a compound represented by the following general formula (1) is protected with an acetal group represented by the following general formula (1-1): [In general formula (1), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １２ is a single bond or a divalent linking group which may have a hetero atom. n is an integer of 1 to 3. In general formula (1-1), R １３ and R １４ are each independently a hydrogen atom or an alkyl group. １５ is a hydrocarbon group. １５ is R １３ or R １４ * represents a bond to the oxygen atom of formula (1).

11. The monomer having an acid-dissociable group is at least represented by the following general formula (2): [In general formula (2), R ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２２ represents a single bond or a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a hetero atom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a hetero atom. ２３ represents a divalent hydrocarbon group having 1 to 30 carbon atoms which may be interrupted by a heteroatom, and some or all of the hydrogen atoms in the hydrocarbon group may be substituted with a group containing a heteroatom. m is an integer of 0 to 2. R ２４ is an acid-dissociable group represented by the following general formula (2-1): [In general formula (2-1), R ２４１ represents a carbon atom. ２４２ is R ２４１ * represents a bond to the oxygen atom in formula (2). ２４３ is an alkyl group or aromatic hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, or a group represented by the following general formula (2-1-1): In general formula (2-1-1), R ２４３１ , R ２４３２ and R ２４３３ are each independently a hydrogen atom or a saturated aliphatic hydrocarbon group. ２４３１ , R ２４３２ and R ２４３３ Two or more of the following may be bonded to each other to form a ring structure. * represents R in formula (2-1). ２４１ The method for producing a polymer according to any one of claims 1 to 10, comprising a monomer represented by the formula:

12. The monomer having a photoacid generating group is represented by the following general formula (3): [In general formula (3), R ３１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ３２ is a single bond or an aromatic hydrocarbon group which may have a substituent. k is 0 or 1. R ３３ represents a single bond or a hydrocarbon group having 1 to 30 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３４ represents a hydrocarbon group having 1 to 15 carbon atoms, and some or all of the hydrogen atoms in the hydrocarbon group may be replaced by fluorine atoms. ３５ , R ３６ and R ３７ each independently represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and some of the carbon atoms contained in the hydrocarbon group may be replaced with a hetero atom or a group containing a hetero atom. ３５ , R ３６ and R ３７ any two or more of which may be bonded to each other to form a ring together with the sulfur atom in formula (3).

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