Positive type resist composition and resist pattern formation method

Abstract

A technology is provided that enables the formation of a resist pattern with low reduction of the resist pattern top and high contrast. As a positive type resist composition, a positive type resist composition comprising copolymer A, copolymer B, and a solvent is used, wherein the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m2 or more.

Description

Technology Field

[0001] The present invention relates to a positive type resist composition and a method for forming a resist pattern. Background Technology

[0002] Conventionally, in fields such as semiconductor manufacturing, a polymer whose main chain is cut by irradiation with ionizing radiation such as electron beams or short-wavelength light such as ultraviolet rays (hereinafter, ionizing radiation and short-wavelength light may be collectively referred to as "ionizing radiation, etc.") and whose solubility in a developer is increased is used as a main chain-cutting positive type resist.

[0003] And, for example, Patent Document 1 discloses a positive resist composition comprising a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units, as a positive resist of a main chain cleavage type having excellent sensitivity to ionizing radiation, etc. and heat resistance. Prior art literature

[0004] Japanese Patent Publication No. 2018-154754 The problem to be solved

[0005] However, the resist pattern formed using the above-mentioned conventional positive-type resist composition had room for improvement in terms of reducing the reduction (top loss) of the resist pattern while simultaneously increasing the contrast of the resist pattern.

[0006] Accordingly, the present invention aims to provide a positive type resist composition capable of forming a resist pattern with low reduction of the resist pattern top and high contrast.

[0007] In addition, the present invention aims to provide a method for forming a resist pattern capable of forming a resist pattern with low reduction of the resist pattern top and high contrast. means of solving the problem

[0008] The inventors have conducted careful examinations to achieve the above objective. Then, the inventors newly discovered that if a positive-type resist composition comprising two types of predetermined copolymers is used as a positive-type resist, the reduction of the resist pattern top is small and a resist pattern with high contrast can be formed, and thus completed the present invention.

[0009] That is, the present invention aims to advantageously solve the above problem, wherein the positive-type resist composition of the present invention comprises copolymer A, copolymer B, and a solvent, and the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m² 2 It is characterized by the above. Thus, it comprises copolymer A, copolymer B, and a solvent, wherein the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m² 2 By using the above positive type resist composition, the reduction of the resist pattern top is small, and a resist pattern with high contrast can be formed.

[0010] Meanwhile, in the present invention, "surface free energy" can be measured using the method described in the embodiments of this specification.

[0011] Here, in the positive-type resist composition of the present invention, at least one of copolymer A and copolymer B is a main chain cleavage type copolymer containing a halogen atom. More preferably, at least one of copolymer A and copolymer B comprises a fluorine substituent, at least one of the halogen atom is a fluorine atom, and the fluorine atom is included in the fluorine substituent.

[0012] If at least one of copolymer A and copolymer B is a main chain cleavage type copolymer containing a halogen atom, and preferably at least one of copolymer A and copolymer B contains a fluorine substituent, and at least one of the halogen atom is a fluorine atom, and said fluorine atom is included in said fluorine substituent, then the reduction of the resist pattern top is further reduced, and a resist pattern with higher contrast can be formed.

[0013] Meanwhile, in the present invention, the statement that the copolymer is "main chain cleavage type" means that the copolymer has the property of having its main chain cleavage when ionizing radiation, such as electron beams or extreme ultraviolet (EUV), is irradiated onto the copolymer.

[0014] Here, it is preferable that the positive-type resist composition of the present invention substantially does not contain a component with a weight-average molecular weight (Mw) of less than 1000. By using a positive-type resist composition that substantially does not contain a component with a weight-average molecular weight (Mw) of less than 1000, the contrast of the resist pattern can be further enhanced.

[0015] Meanwhile, in the present invention, the “weight average molecular weight” can be measured as a standard polystyrene equivalent value using gel permeation chromatography.

[0016] In addition, in the present invention, "substantially not included" means not actively incorporated except in cases where it is inevitably incorporated. Specifically, it refers to a positive-type resist composition in which the content ratio of a component having a weight average molecular weight (Mw) of less than 1000 is less than 0.05 mass%.

[0017] In addition, the positive-type resist composition of the present invention comprises at least one of the copolymer A and the copolymer B, the following formula (V):

[0018] [Chemical Formula 1]

[0019]

[0020] [In formula (V), X is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or an alkyl halide group, and R 1 It is preferable to have a monomer unit (V) represented as [an organic group having 3 or more and 10 or fewer fluorine atoms]. If at least one of copolymer A and copolymer B has a monomer unit (V), the contrast of the resist pattern can be further enhanced.

[0021] In addition, the positive-type resist composition of the present invention comprises, wherein the copolymer A is of the following formula (I):

[0022] [Chemical Formula 2]

[0023]

[0024] A monomer unit (I) represented by [wherein L is a divalent linker having a fluorine atom, and Ar is an aromatic ring that may have a substituent] and the following formula (II):

[0025] [Chemical Formula 3]

[0026]

[0027] [In Equation (II), R 1 It is an alkyl group, and R 2 is a hydrogen atom, an alkyl group, a halogen atom, an alkyl halide group, a hydroxyl group, a carboxyl group, or a carboxyl halide group, and R 3 It is preferable to have a monomer unit (II) represented as follows: [It is an alkyl group substituted with a hydrogen atom, an unsubstituted alkyl group, or a fluorine atom, and p and q are integers from 0 to 5, and p + q = 5.]. By using copolymer A having monomer unit (I) and monomer unit (II), the contrast of the resist pattern can be further enhanced.

[0028] Meanwhile, in the present invention, "may have a substituent" means "non-substituent, or having a substituent."

[0029] In addition, the positive-type resist composition of the present invention comprises, wherein the copolymer B is of the following formula (III):

[0030] [Chemical Formula 4]

[0031]

[0032] [In Equation (III), R 1 A monomer unit (III) represented as [an organic group having 5 or more and 7 or less fluorine atoms] and the following formula (IV):

[0033] [Chemical Formula 5]

[0034]

[0035] [In Equation (IV), R 1 It is an alkyl group, and R 2 is a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and R 3 It is preferable to have a monomer unit (IV) represented as follows: [It is an alkyl group substituted with a hydrogen atom, an unsubstituted alkyl group, or a fluorine atom, and p and q are integers from 0 to 5, and p + q = 5.]. By using copolymer B having monomer unit (III) and monomer unit (IV), the contrast of the resist pattern can be further enhanced.

[0036] Furthermore, the present invention aims to advantageously solve the above problem. The method for forming a resist pattern according to the present invention is characterized by comprising the steps of: forming a resist film using any one of the positive-type resist compositions described above; exposing the resist film to light; and developing the exposed resist film. In this way, by forming a resist film using the positive-type resist composition of the present invention, exposing the obtained resist film to light, and then developing the exposed resist film, it is possible to form a resist pattern with low reduction of the resist pattern top and high contrast.

[0037] Furthermore, in the resist pattern forming method of the present invention, it is preferable to perform the above-mentioned development using alcohol. By developing with alcohol, the contrast of the resist pattern can be further enhanced. Effects of the invention

[0038] According to the present invention, a positive resist composition capable of forming a resist pattern with low reduction of the resist pattern top and high contrast can be provided.

[0039] In addition, according to the present invention, a method for forming a resist pattern can be provided that has a small reduction in the resist pattern top and can also form a resist pattern with high contrast. Specific details for implementing the invention

[0040] Hereinafter, embodiments of the present invention will be described in detail.

[0041] Here, the positive-type resist composition of the present invention is used to form a resist film when forming a resist pattern using ionizing radiation such as electron beams or EUV. Furthermore, the method for forming a resist pattern of the present invention is to form a resist pattern using the positive-type resist composition of the present invention. Here, the method for forming a resist pattern of the present invention is not particularly limited and can be used, for example, when forming a resist pattern in a manufacturing process for semiconductors, photomasks, molds, etc.

[0042] (Positive-type resist composition)

[0043] The positive-type resist composition of the present invention comprises copolymer A and copolymer B, which are described in detail below, and a solvent, and optionally further comprises a known additive that can be incorporated into the positive-type resist composition.

[0044] And, the positive-type resist composition of the present invention comprises copolymer A and copolymer B, and the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m² 2 It is necessary to have the above. And, the positive-type resist composition of the present invention has a difference in surface free energy of 4 mJ / m 2 Since the copolymer A and copolymer B described above are contained as a positive-type resist, using the positive-type resist composition can reduce the reduction of the resist pattern top and form a high-contrast resist pattern.

[0045] In addition, the positive-type resist composition of the present invention preferably does not substantially contain a component having a weight average molecular weight (Mw) of less than 1000, and specifically, the content ratio of the component having a weight average molecular weight (Mw) of less than 1000 in the positive-type resist composition is less than 0.05 mass%, less than 0.01 mass%, and more preferably less than 0.001 mass%.

[0046] Copolymer A

[0047] Copolymer A included in the positive-type resist composition of the present invention has a difference of 4 mJ / m² between the surface free energy of copolymer A and the surface free energy of copolymer B. 2 As such, it is not particularly limited. Furthermore, in order to form a resist pattern with less reduction of the resist pattern top and higher contrast, copolymer A is preferably a main chain cleavage type copolymer containing a halogen atom, and more preferably comprises a fluorine substituent, wherein at least one of the halogen atoms is a fluorine atom and said fluorine atom is included in said fluorine substituent. Here, the fluorine substituent is not particularly limited as long as it is a substituent having a fluorine atom.

[0048] [Surface Free Energy of Copolymer A]

[0049] Here, the surface free energy of copolymer A is 28 mJ / m² 2 It is desirable that it be above 29 mJ / m 2 It is more desirable to have an ideal value of 30 mJ / m² 2 It is more desirable to have an ideal value of 35 mJ / m² 2 It is desirable that it be less than or equal to 34 mJ / m² 2 It is more desirable that it be less than or equal to 33 mJ / m 2 It is more desirable to be less than this.

[0050] In addition, copolymer A included in the positive type resist composition of the present invention is, in terms of further enhancing the contrast of the resist pattern, the following formula (V):

[0051] [Chemical Formula 6]

[0052]

[0053] [In formula (V), X is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or an alkyl halide group, and R 1 It is preferable to have a monomer unit (V) represented as [an organic group having 3 or more and 10 or fewer fluorine atoms].

[0054] Here, the monomer unit (V) is given by the following formula (e):

[0055] [Chemical Formula 7]

[0056]

[0057] [In Equation (e), X and R 1 It is a structural unit derived from a monomer (e) represented by [V].

[0058] In addition, the ratio of monomer unit (e) among the total monomer units constituting copolymer A is not particularly limited and, for example, can be 30 mol% or more, preferably 40 mol% or more, more preferably 45 mol% or more, can be 70 mol% or less, preferably 60 mol% or less, and more preferably 55 mol% or less.

[0059] Here, halogen atoms that can constitute X in formulas (V) and (e) may include, for example, chlorine atoms, fluorine atoms, bromine atoms, iodine atoms, or astatine atoms. Additionally, alkylsulfonyl groups that can constitute X in formulas (V) and (e) may include, for example, methylsulfonyl groups or ethylsulfonyl groups. Additionally, alkoxy groups that can constitute X in formulas (V) and (e) may include, for example, methoxy groups, ethoxy groups, or propoxy groups. Additionally, acyl groups that can constitute X in formulas (V) and (e) may include formyl groups, acetyl groups, or propionyl groups. Additionally, alkyl ester groups that can constitute X in formulas (V) and (e) may include methyl ester groups or ethyl ester groups. In addition, alkyl halide groups that can constitute X in formulas (V) and (e) may include, for example, methyl halide groups having 1 or more and 3 or fewer halogen atoms.

[0060] Among them, it is preferable that X be a halogen atom, and more preferable that X be a chlorine atom.

[0061] Also, R in equations (V) and (e) 1 It is an organic group having 3 or more and 10 or less fluorine atoms, and R 1 The number of fluorine atoms included in is preferably 5 or more and 7 or less. R 1 If the number of fluorine atoms included therein is greater than or equal to the above lower limit, copolymer A is useful as a main chain cleavage type positive resist. In addition, R 1 If the number of fluorine atoms included is less than or equal to the upper limit value, the manufacturing efficiency of copolymer A is excellent.

[0062] Organic groups having 3 to 10 (preferably 5 to 7) fluorine atoms are not particularly limited and may include, for example, fluoroalkyl groups having 3 to 10 fluorine atoms, such as (a-1) to (a-30) below; fluoroalkoxyalkyl groups having 3 to 10 fluorine atoms, such as (a-31) to (a-54) below; fluoroalkoxyalkenyl groups having 3 to 10 fluorine atoms, such as fluoroethoxyvinyl groups; and organic groups represented by the following formula (A) (hereinafter referred to as “organic group (A)”).

[0063] -L-Ar ···(A)

[0064] [In the organic group (A), L is a divalent linker and Ar is an aromatic ring that may have a substituent, and the number of fluorine atoms included in the organic group (A) is 3 or more and 10 or less (preferably 5 or more and 7 or less).]

[0065] [Chemical Formula 8]

[0066]

[0067] [Chemical Formula 9]

[0068]

[0069] The divalent linking group that can constitute L in the organic group (A) is not particularly limited, and examples include an alkylene group that may have a substituent, an alkenylene group that may have a substituent, etc.

[0070] In addition, the alkylene groups that may have substituents are not particularly limited, and examples include chain-type alkylene groups such as methylene groups, ethylene groups, propylene groups, n-butylene groups, and isobutylene groups, and cyclic alkylene groups such as 1,4-cyclohexylene groups. Among these, as the alkylene groups, chain-type alkylene groups having 1 to 6 carbon atoms, such as methylene groups, ethylene groups, propylene groups, n-butylene groups, and isobutylene groups, are preferred; straight-chain alkylene groups having 1 to 6 carbon atoms, such as methylene groups, ethylene groups, propylene groups, and n-butylene groups, are more preferred; and straight-chain alkylene groups having 1 to 3 carbon atoms, such as methylene groups, ethylene groups, and propylene groups, are even more preferred.

[0071] In addition, the alkenylene groups that may have substituents are not particularly limited, and examples include chain-type alkenylene groups such as ethenylene groups, 2-propenylene groups, 2-butenylene groups, and 3-butenylene groups, and cyclic alkenylene groups such as cyclohexanylene groups. Among these, as the alkenylene groups, straight-chain alkenylene groups having 2 to 6 carbon atoms, such as ethenylene groups, 2-propenylene groups, 2-butenylene groups, and 3-butenylene groups, are preferred.

[0072] Among the above, from the perspective of sufficiently improving the sensitivity of the obtained copolymer A to ionizing radiation, etc., as a divalent linker, an alkylene group having a substituent is preferred, a chain-type alkylene group having 1 to 6 carbon atoms having a substituent is more preferred, a straight-chain alkylene group having 1 to 6 carbon atoms having a substituent is even more preferred, and a straight-chain alkylene group having 1 to 3 carbon atoms having a substituent is particularly preferred.

[0073] In addition, from the perspective of further improving the sensitivity of copolymer A to ionizing radiation, etc., it is desirable that the divalent linker capable of constituting L of the organic group (A) has one or more electron-withdrawing groups. Among these, when the divalent linker is an alkylene group having an electron-withdrawing group as a substituent or an alkenylene group having an electron-withdrawing group as a substituent, it is desirable that the electron-withdrawing group is bonded to a carbon that is bonded to O adjacent to the carbonyl carbon in formula (V).

[0074] Meanwhile, the electron-attracting group capable of sufficiently improving sensitivity to ionizing radiation, etc., is not particularly limited, and for example, at least one selected from the group consisting of a fluorine atom, a fluoroalkyl group, a cyano group, and a nitro group may be cited. In addition, the fluoroalkyl group is not particularly limited, and for example, a fluoroalkyl group having 1 to 5 carbon atoms may be cited. Among these, as the fluoroalkyl group, a perfluoroalkyl group having 1 to 5 carbon atoms is preferred, and a trifluoromethyl group is more preferred.

[0075] And, from the perspective of further increasing the productivity of copolymer A, as for L in the organic group (A), a divalent linker containing 3 or more and 10 or fewer fluorine atoms is preferred, a divalent linker containing 3 or more and 6 or fewer fluorine atoms is more preferred, and a trifluoromethylmethylene group, a pentafluoroethylmethylene group, or a bis(trifluoromethyl)methylene group is even more preferred.

[0076] In addition, among the organic groups (A), Ar can be an aromatic hydrocarbon group that may have a substituent and an aromatic heterocyclic group that may have a substituent.

[0077] In addition, aromatic hydrocarbon groups are not particularly limited and examples include benzene groups, biphenyl groups, naphthalene groups, azulene groups, anthracene groups, phenanthrene groups, pyrene groups, chrysene groups, naphthacene groups, triphenylene groups, o-terphenyl groups, m-terphenyl groups, p-terphenyl groups, acenaphthene groups, coronene groups, fluorene groups, fluoranthrene groups, pentacene groups, perylene groups, pentaphene groups, physene groups, pyranthrene groups, etc.

[0078] In addition, aromatic complex groups are not particularly limited and may include, for example, furan groups, thiophene groups, pyridine groups, pyridazine groups, pyrimidine groups, pyrazine groups, triazine groups, oxadiazole groups, triazole groups, imidazole groups, pyrazol groups, thiazole groups, indole groups, benzimidazole groups, benzothiazole groups, benzoxazole groups, quinoxaline groups, quinazolin groups, phthalazine groups, benzofuran groups, dibenzofuran groups, benzothiophene groups, dibenzothiophene groups, carbazole groups, etc.

[0079] In addition, the substituents that Ar can have are not particularly limited, and examples include alkyl groups, fluorine atoms, and fluoroalkyl groups. Also, alkyl groups that Ar can have as substituents include, for example, chain-type alkyl groups having 1 to 6 carbon atoms, such as methyl groups, ethyl groups, propyl groups, n-butyl groups, and isobutyl groups. In addition, fluoroalkyl groups that Ar can have as substituents include, for example, fluoroalkyl groups having 1 to 5 carbon atoms, such as trifluoromethyl groups, trifluoroethyl groups, and pentafluoropropyl groups.

[0080] Among these, from the perspective of increasing the ease of manufacturing copolymer A, for Ar in the organic group (A), an aromatic hydrocarbon group that may have a substituent is preferred, an unsubstituted aromatic hydrocarbon group is more preferred, and a benzene group (phenyl group) is even more preferred.

[0081] And, the monomer (e) represented by formula (V) is not particularly limited and, for example, α-chloroacrylic acid fluoroalkyl esters such as α-chloroacrylic acid 2,2,2-trifluoroethyl, α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-chloroacrylic acid 3,3,4,4,4-pentafluorobutyl, α-chloroacrylic acid 1H-1-(trifluoromethyl)trifluoroethyl, α-chloroacrylic acid 1H,1H,3H-hexafluorobutyl, α-chloroacrylic acid 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl, α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl; Examples include α-chloroacrylate fluoroalkoxyalkyl esters such as α-chloroacrylate pentafluoroethoxymethyl ester and α-chloroacrylate pentafluoroethoxyethyl ester; α-chloroacrylate fluoroalkoxyalkenyl esters such as α-chloroacrylate pentafluoroethoxyvinyl ester; α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl, α-chloroacrylate-1-phenyl-2,2,2-trifluoroethyl, α-chloroacrylate-1-phenyl-2,2,2-trifluoroethyl, α-chloroacrylate-1-phenyl-2,2,3,3,3-pentafluoropropyl, etc. And, from the perspective of further increasing the manufacturing efficiency of copolymer A, the monomer (e) represented by formula (V) is preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl, α-chloroacrylic acid-1-phenyl-2,2,2-trifluoroethyl, or α-chloroacrylic acid-1-phenyl-2,2,3,3,3-pentafluoropropyl, and more preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl, or α-chloroacrylic acid-1-phenyl-2,2,3,3,3-pentafluoropropyl.

[0082] In addition, copolymer A included in the positive type resist composition of the present invention is, in terms of further enhancing the contrast of the resist pattern, the following formula (I):

[0083] [Chemical Formula 10]

[0084]

[0085] A monomer unit (I) represented by [wherein L is a divalent linker having a fluorine atom and Ar is an aromatic group that may have a substituent] and the following formula (II):

[0086] [Chemical Formula 11]

[0087]

[0088] [In Equation (II), R 1 It is an alkyl group, and R 2 is a hydrogen atom, an alkyl group, a halogen atom, an alkyl halide group, a hydroxyl group, a carboxyl group, or a carboxyl halide group, and R 3 It is more preferable to have a monomer unit (II) represented as follows: [silver, hydrogen atom, unsubstituted alkyl group or alkyl group substituted with a fluorine atom, p and q are integers from 0 to 5, and p + q = 5.]

[0089] Meanwhile, copolymer A may include any monomer unit other than monomer unit (I) and monomer unit (II), and the proportion of monomer unit (I) and monomer unit (II) among the total monomer units constituting copolymer A is preferably 90 mol% or more in total, and more preferably 100 mol% (i.e., copolymer A contains only monomer unit (I) and monomer unit (II)).

[0090] In addition, copolymer A contains monomer units (I) and monomer units (II), so that when irradiated with electron beams, etc., the main chain is cleaved and efficiently reduced to a low molecular weight.

[0091] Here, the monomer unit (I) is given by the following formula (a):

[0092] [Chemical Formula 12]

[0093]

[0094] It is a structural unit derived from monomer (a) represented by [wherein L and Ar are identical to in formula (I).]

[0095] Here, as a divalent linker having a fluorine atom that can constitute L in formulas (I) and (a), examples include a divalent chain-type alkyl group having 1 to 5 carbon atoms having a fluorine atom. In addition, the number of fluorine atoms is preferably 3 or more and 10 or less, and 5 or more and 7 or less.

[0096] In addition, aromatic rings that may have substituents and can constitute Ar in Equation (I) and Equation (a) include aromatic hydrocarbon rings that may have substituents and aromatic complex rings that may have substituents.

[0097] In addition, aromatic hydrocarbon groups are not particularly limited, and, for example, groups identical to the aromatic hydrocarbon groups that can constitute Ar in the above-described formulas (V) and (e) may be cited.

[0098] In addition, aromatic complex generators are not particularly limited, and, for example, any aromatic complex generator identical to Ar in the above-described equations (V) and (e) can be used.

[0099] In addition, the substituents that Ar can have are not particularly limited, and, for example, groups identical to the substituents that Ar can have in the above-described formulas (V) and (e) can be cited.

[0100] Among these, from the perspective of sufficiently improving sensitivity to electron beams, etc., for Ar in formulas (I) and (a), an aromatic hydrocarbon group that may have a substituent is preferred, an unsubstituted aromatic hydrocarbon group is more preferred, and a benzene group (phenyl group) is even more preferred.

[0101] And, from the perspective of sufficiently improving sensitivity to electron beams, etc., the monomer (a) represented by the formula (a) described above, which can form the monomer unit (I) represented by the formula (I) described above, is preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) and α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPhOMe), and more preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl. That is, copolymer A preferably has at least one of an α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl unit and an α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl unit, and more preferably has an α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl unit.

[0102] Meanwhile, the ratio of monomer unit (I) among the total monomer units constituting copolymer A is not particularly limited and, for example, can be 30 mol% or more, is preferably 40 mol% or more, is more preferably 45 mol% or more, can be 70 mol% or less, is preferably 60 mol% or less, and is more preferably 55 mol% or less.

[0103] In addition, the monomer unit (II) is the following formula (b):

[0104] [Chemical Formula 13]

[0105]

[0106] [In Equation (b), R 1 and R 2 ..., and, p and q are the same as in formula (II).] is a structural unit derived from monomer (b).

[0107] Here, R in Equation (II) and Equation (b) 1 , R2 The alkyl groups that can constitute are not particularly limited, and examples include unsubstituted alkyl groups having 1 to 5 carbon atoms. Among these, R 1 , R 2 As for the alkyl groups that can constitute it, methyl or ethyl groups are preferred.

[0108] Also, R in Equation (II) and Equation (b) 2 The halogen atoms that can constitute it are not particularly limited and include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. Among these, fluorine atoms are preferred as halogen atoms.

[0109] Also, R in Equation (II) and Equation (b) 2 The alkyl halide groups that can constitute the group are not particularly limited, and examples include fluoroalkyl groups having 1 to 5 carbon atoms. Among these, perfluoroalkyl groups having 1 to 5 carbon atoms are preferred as alkyl halide groups, and trifluoromethyl groups are more preferred.

[0110] Also, R in Equation (II) and Equation (b) 2 Halogenated carboxyl groups that can constitute the structure are not particularly limited, and examples include chloride carboxyl groups (-C(=O)-Cl), fluoride carboxyl groups (-C(=O)-F), bromide carboxyl groups (-C(=O)-Br), etc.

[0111] And, in terms of improving the ease of preparation of copolymer A and the cleavage of the main chain when irradiated with electron beams, etc., R in formulas (II) and (b) 1 It is preferable that the silver be an alkyl group having 1 to 5 carbon atoms, and more preferable that it be a methyl group.

[0112] In addition, from the perspective of improving the ease of preparation of copolymer A and the cleavage of the main chain when irradiated with electron beams, etc., it is preferable that p in formula (II) and formula (b) be 0 or 1.

[0113] In addition, if p in Equation (II) and Equation (b) is any one of 1 to 5, R in Equation (II) and Equation (b) 2 It is preferable that it be an alkyl group having 1 to 5 carbon atoms, and more preferable that it be a methyl group.

[0114] Also, R in equations (II) and (b) 3 The unsubstituted alkyl groups that can constitute are not particularly limited, and may include unsubstituted alkyl groups having 1 to 5 carbon atoms. Among these, R 3 As for the unsubstituted alkyl groups that can constitute it, a methyl group or an ethyl group is preferred.

[0115] Also, R in equations (II) and (b) 3 An alkyl group substituted with a fluorine atom that can constitute it is not particularly limited, and may include a group having a structure in which some or all of the hydrogen atoms in the alkyl group are substituted with a fluorine atom.

[0116] In addition, the monomer (b) represented by the formula (b) described above, which can form the monomer unit (II) represented by the formula (II) described above, is not particularly limited and, for example, α-methylstyrene (AMS) and its derivatives such as the following monomers (b-1) to (b-12) may be used.

[0117] [Chemical Formula 14]

[0118]

[0119] Meanwhile, from the perspective of improving the ease of preparation of copolymer A and the cleavage of the main chain when irradiated with electron beams, etc., α-methylstyrene is preferred as the monomer (b) represented by the formula (b) described above, which can form monomer units (II). That is, copolymer A is preferred to have α-methylstyrene units.

[0120] And, the ratio of monomer unit (II) among the total monomer units constituting copolymer A is not particularly limited, and, for example, can be 30 mol% or more, is 40 mol% or more, is more preferably 45 mol% or more, can be 70 mol% or less, is 60 mol% or less, and is more preferably 55 mol% or less.

[0121] <Properties of Copolymer A>

[0122] [Weight Average Molecular Weight (Mw)]

[0123] The weight average molecular weight (Mw) of copolymer A is preferably 100,000 or more, more preferably 125,000 or more, even more preferably 150,000 or more, preferably 600,000 or less, and more preferably 500,000 or less. If the weight average molecular weight (Mw) of copolymer A is greater than or equal to the lower limit value, the reduction of the resist pattern top is further reduced, and a resist pattern with further improved contrast can be formed. In addition, if the weight average molecular weight (Mw) of copolymer A is less than or equal to the upper limit value, the adjustment of the positive-type resist composition can be facilitated.

[0124] [Number Average Molecular Weight (Mn)]

[0125] The number average molecular weight (Mn) of copolymer A is preferably 100,000 or more, more preferably 110,000 or more, preferably 300,000 or less, and more preferably 200,000 or less. If the number average molecular weight of copolymer A is greater than or equal to the lower limit value, the reduction of the resist pattern top can be further reduced, and a resist pattern with further improved contrast can be formed. In addition, if the number average molecular weight of copolymer A is less than or equal to the upper limit value, the preparation of a positive-type resist composition becomes easier.

[0126] [Molecular Weight Distribution (Mw / Mn)]

[0127] In addition, the molecular weight distribution (Mw / Mn) of copolymer A is preferably 1.20 or higher, more preferably 1.25 or higher, even more preferably 1.30 or higher, preferably 2.00 or lower, more preferably 1.80 or lower, and even more preferably 1.60 or lower.

[0128] Meanwhile, in the present invention, the "number average molecular weight" can be measured as a standard polystyrene equivalent value using gel permeation chromatography, and the "molecular weight distribution" can be obtained by calculating the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight).

[0129] [Method for preparing copolymer A]

[0130] The method of preparing copolymer A is not particularly limited. For example, copolymer A having the monomer unit (V) described above can be prepared by polymerizing a monomer composition comprising monomer (e) and any monomer copolymerizable with monomer (e), recovering the obtained copolymer, and optionally purifying it.

[0131] Meanwhile, the composition, molecular weight distribution, number average molecular weight, and weight average molecular weight of copolymer A can be adjusted by changing the polymerization and purification conditions. Specifically, for example, the number average molecular weight and weight average molecular weight can be increased by lowering the polymerization temperature. Additionally, the number average molecular weight and weight average molecular weight can be increased by shortening the polymerization time. Furthermore, the molecular weight distribution can be reduced by performing purification.

[0132] Polymerization of Monomer Composition

[0133] Here, as the monomer composition used for preparing copolymer A, for example, a mixture of a monomer component comprising monomer (e) and any monomer copolymerizable with monomer (e), an optionally usable solvent, an optionally usable polymerization initiator, and optionally added additives may be used. Furthermore, the polymerization of the monomer composition may be carried out using known methods. Among these, it is preferable to use cyclopentanone, water, etc., as the solvent.

[0134] In addition, the polymer obtained by polymerizing the monomer composition is not particularly limited and can be recovered by adding a solvent such as tetrahydrofuran to a solution containing the polymer, and then dropping the solution containing the solvent into a non-solvent such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, or hexane to coagulate the polymer.

[0135] Purification of Polymers

[0136] Meanwhile, the purification method used to purify the obtained polymer is not particularly limited, and known purification methods such as reprecipitation or column chromatography may be used. Among these, it is preferable to use the reprecipitation method as the purification method.

[0137] Meanwhile, the purification of the polymer may be repeated multiple times.

[0138] In addition, purification of the polymer by the reprecipitation method is preferably carried out by, for example, dissolving the obtained polymer in a solvent such as tetrahydrofuran, and then adding the resulting solution dropwise to a mixed solvent of a solvent such as tetrahydrofuran and a co-solvent such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, or hexane, thereby precipitating a portion of the polymer. In this way, purification is performed by adding the polymer solution dropwise to a mixed solvent of a solvent and a co-solvent, thereby easily adjusting the molecular weight distribution, number average molecular weight, and weight average molecular weight of the obtained copolymer A by changing the types or mixing ratios of the solvent and the co-solvent. Specifically, for example, the molecular weight of the copolymer precipitated in the mixed solvent can be increased as the ratio of the solvent in the mixed solvent increases.

[0139] Meanwhile, when purifying the polymer by the reprecipitation method, as copolymer A, provided that the desired properties are satisfied, a polymer precipitated in a mixed solvent of both solvents and a co-solvent may be used, or a polymer that has not precipitated in the mixed solvent (i.e., a polymer dissolved in the mixed solvent) may be used. Here, the polymer that has not precipitated in the mixed solvent can be recovered from the mixed solvent using known methods such as concentration and drying.

[0140] Copolymer B

[0141] Copolymer B included in the positive-type resist composition of the present invention has a difference of 4 mJ / m² between the surface free energy of copolymer B and the surface free energy of copolymer A. 2As such, it is not particularly limited. Furthermore, in order to form a resist pattern with less reduction of the resist pattern top and higher contrast, copolymer B is preferably a main chain cleavage type copolymer containing a halogen atom, and more preferably contains a fluorine substituent, wherein at least one of the halogen atoms is a fluorine atom and said fluorine atom is included in said fluorine substituent. Here, the fluorine substituent is not particularly limited as long as it is a substituent having a fluorine atom.

[0142] [Surface Free Energy of Copolymer B]

[0143] Here, the surface free energy of copolymer B is 18 mJ / m² 2 It is desirable that it be above 19 mJ / m 2 It is more desirable to have an ideal value of 20 mJ / m² 2 It is more desirable for it to be above 27 mJ / m 2 It is desirable that it be less than or equal to 26 mJ / m² 2 It is more desirable that it be less than or equal to 25 mJ / m² 2 It is more desirable to be less than this.

[0144] And, the difference between the surface free energy of copolymer B and the surface free energy of copolymer A [i.e., the value of (surface free energy of copolymer A) - (surface free energy of copolymer B)] is 4 mJ / m² 2 It needs to be above that, and this car is 5.5 mJ / m 2 It is desirable that it be above 6 mJ / m 2 It is more desirable to be above 6.5 mJ / m 2 It is more desirable to have an amount greater than 12 mJ / m² 2 It is desirable that it be less than or equal to 11 mJ / m² 2 It is more desirable that it be less than or equal to 10 mJ / m 2 It is more desirable to be less than this.

[0145] Furthermore, from the perspective of further enhancing the contrast of the resist pattern, it is preferable that copolymer B has a monomer unit (V) represented by formula (V) as described in the section on <Copolymer A>. Meanwhile, since the monomer unit (V) that copolymer B may have can be identical to the monomer unit (V) described in the section on <Copolymer A>, a description thereof is omitted here.

[0146] In addition, the proportion of monomer unit (e) among the total monomer units constituting copolymer B is not particularly limited and, for example, can be 30 mol% or more, preferably 40 mol% or more, more preferably 45 mol% or more, can be 70 mol% or less, preferably 60 mol% or less, and more preferably 55 mol% or less.

[0147] And, copolymer B included in the positive type resist composition of the present invention, in terms of further enhancing the contrast of the resist pattern, is of the following formula (III):

[0148] [Chemical Formula 15]

[0149]

[0150] [In Equation (III), R 1 A monomer unit (III) represented as [an organic group having 5 or more and 7 or less fluorine atoms] and the following formula (IV):

[0151] [Chemical Formula 16]

[0152]

[0153] [In Equation (IV), R 1 It is an alkyl group, and R 2 is a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and R 3It is more preferable to have a monomer unit (IV) represented as follows: [silver, hydrogen atom, unsubstituted alkyl group or alkyl group substituted with a fluorine atom, p and q are integers from 0 to 5, and p + q = 5.]

[0154] Meanwhile, copolymer B may include any monomer unit other than monomer unit (III) and monomer unit (IV), and the proportion of monomer unit (III) and monomer unit (IV) among the total monomer units constituting copolymer B is preferably 90 mol% or more in total, and more preferably 100 mol% (i.e., copolymer B contains only monomer unit (III) and monomer unit (IV)).

[0155] Furthermore, copolymer B comprises monomer units (III) and monomer units (IV), so that when irradiated with electron beams or the like, the main chain is cleaved and efficiently reduced to a low molecular weight. Additionally, copolymer B preferably has monomer units (III) that have fluorine atoms, so that when using the positive-type resist composition of the present invention, the surface free energy of copolymer B can be easily adjusted, and it has resistance to forward scattering, back scattering, and leakage light such as EUV caused by electron beams, thereby increasing the contrast of the pattern.

[0156] <Monomer Unit (III)>

[0157] Here, the monomer unit (III) is given by the following formula (c):

[0158] [Chemical Formula 17]

[0159]

[0160] [In Equation (c), R 1 It is a structural unit derived from a monomer (c) represented by [It is identical to formula (III).]

[0161] Also, among Equations (II) and (c), R 1The number of carbon atoms is preferably 2 or more and 10 or less, and more preferably 5 or less. If the number of carbon atoms is greater than or equal to the lower limit value, the solubility in the developer can be sufficiently improved. In addition, if the number of carbon atoms is less than or equal to the upper limit value, the clarity of the resist pattern can be sufficiently guaranteed.

[0162] Specifically, R in Equation (III) and Equation (c) 1 It is preferable that it be silver, a fluoroalkyl group, a fluoroalkoxyalkyl group, or a fluoroalkoxyalkenyl group, and more preferable that it be a fluoroalkyl group. R 1 With the above-described mechanism, the cleavage ability of the main chain of copolymer B can be sufficiently improved when irradiated with electron beams, etc.

[0163] Here, examples of fluoroalkyl groups include, for instance, 2,2,3,3,3-pentafluoropropyl group (5 fluorine atoms, 3 carbon atoms), 3,3,4,4,4-pentafluorobutyl group (5 fluorine atoms, 4 carbon atoms), 1H-1-(trifluoromethyl)trifluoroethyl group (6 fluorine atoms, 3 carbon atoms), 1H,1H,3H-hexafluorobutyl group (6 fluorine atoms, 4 carbon atoms), 2,2,3,3,4,4,4-heptafluorobutyl group (7 fluorine atoms, 4 carbon atoms), and 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl group (7 fluorine atoms, 3 carbon atoms). Among these, a 2,2,3,3,3-pentafluoropropyl group (5 fluorine atoms and 3 carbon atoms) or a 2,2,3,3,4,4,4-heptafluorobutyl group (7 fluorine atoms and 4 carbon atoms) is preferred, and a 2,2,3,3,3-pentafluoropropyl group (5 fluorine atoms and 3 carbon atoms) is more preferred.

[0164] In addition, fluoroalkoxyalkyl groups include, for example, fluoroethoxymethyl groups and fluoroethoxyethyl groups.

[0165] In addition, fluoroalkoxyalkenyl groups include, for example, fluoroethoxyvinyl groups.

[0166] And, the monomer (c) represented by the formula (c) described above, capable of forming the monomer unit (III) represented by the formula (III) described above, is not particularly limited and, for example, α-chloroacrylic acid fluoroalkyl esters such as α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-chloroacrylic acid 3,3,4,4,4-pentafluorobutyl, α-chloroacrylic acid 1H-1-(trifluoromethyl)trifluoroethyl, α-chloroacrylic acid 1H,1H,3H-hexafluorobutyl, α-chloroacrylic acid 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl, α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl; Examples include α-chloroacrylate fluoroalkoxyalkyl esters such as α-chloroacrylate pentafluoroethoxymethyl ester and α-chloroacrylate pentafluoroethoxyethyl ester; α-chloroacrylate fluoroalkoxyalkenyl esters such as α-chloroacrylate pentafluoroethoxyvinyl ester; etc.

[0167] Meanwhile, in order to further improve the cleavage ability of the main chain of copolymer B when irradiated with electron beams, etc., it is preferable that the monomer unit (III) be a structural unit derived from α-chloroacrylate fluoroalkyl ester.

[0168] And, the ratio of monomer unit (III) among the total monomer units constituting copolymer B is not particularly limited, and, for example, can be 30 mol% or more, is 40 mol% or more, is more preferably 45 mol% or more, can be 70 mol% or less, is 60 mol% or less, and is more preferably 55 mol% or less.

[0169] In addition, the monomer unit (IV) is the following general formula (d):

[0170] [Chemical Formula 18]

[0171]

[0172] [In Equation (d), R 1 ~R 3 , and, p and q are structural units derived from monomer (d) represented by (IV).

[0173] Here, R in Equation (IV) and Equation (d) 1 Examples of alkyl groups that can constitute are not particularly limited, but include alkyl groups having 1 to 5 carbon atoms. Among these, R 1 As for the alkyl groups that can constitute it, methyl or ethyl groups are preferred.

[0174] Also, R in equations (IV) and (d) 2 , R 3 The unsubstituted alkyl groups that can constitute are not particularly limited, and may include unsubstituted alkyl groups having 1 to 5 carbon atoms. Among these, R 2 , R 3 As for the unsubstituted alkyl groups that can constitute it, a methyl group or an ethyl group is preferred.

[0175] Also, R in equations (IV) and (d) 2 , R 3 An alkyl group substituted with a fluorine atom that can constitute it is not particularly limited, and may include a group having a structure in which some or all of the hydrogen atoms in the alkyl group are substituted with a fluorine atom.

[0176] And, from the perspective of improving the ease of preparation of copolymer B, R present in multiple places in formulas (IV) and (d) 2 and / or R 3 It is preferable that the entire group be a hydrogen atom or an unsubstituted alkyl group, and it is preferable that the hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms is a hydrogen atom or an unsubstituted alkyl group, and it is preferable that the hydrogen atom is a hydrogen atom.

[0177] And, the monomer (d) represented by the formula (d) described above, which can form the monomer unit (IV) represented by the formula (IV) described above, is not particularly limited and, for example, α-methylstyrene (AMS) and its derivatives (e.g., 4-fluoro-α-methylstyrene: 4FAMS), such as the following monomers (d-1) to (d-11).

[0178] [Chemical Formula 19]

[0179]

[0180] Meanwhile, from the perspective of improving the ease of preparation of copolymer B and the cleavage of the main chain when irradiated with electron beams, etc., the monomer (d) represented by the above formula (d) capable of forming monomer units (IV) is preferably α-methylstyrene or 4-fluoro-α-methylstyrene. That is, copolymer B is preferably to have α-methylstyrene units or 4-fluoro-α-methylstyrene units.

[0181] And, the ratio of monomer unit (IV) among the total monomer units constituting copolymer B is not particularly limited, and, for example, can be 30 mol% or more, is 40 mol% or more, is more preferably 45 mol% or more, can be 70 mol% or less, is 60 mol% or less, and is more preferably 55 mol% or less.

[0182] <Properties of Copolymer B>

[0183] [Weight Average Molecular Weight (Mw)]

[0184] The weight average molecular weight (Mw) of copolymer B is preferably 10,000 or more, more preferably 17,000 or more, even more preferably 25,000 or more, preferably 250,000 or less, even more preferably 180,000 or less, and even more preferably 50,000 or less. If the weight average molecular weight (Mw) of copolymer B is greater than or equal to the lower limit value above, the solubility of the resist film in the developer solution can be suppressed from becoming excessively high at a low irradiation dose. In addition, if the weight average molecular weight (Mw) of copolymer B is less than or equal to the upper limit value above, the preparation of a positive-type resist composition is easy.

[0185] [Number Average Molecular Weight (Mn)]

[0186] The number average molecular weight (Mn) of copolymer B is preferably 7,000 or higher, more preferably 10,000 or higher, and preferably 150,000 or lower. If the number average molecular weight of copolymer B is above the lower limit value, the solubility of the resist film in the developer can be further suppressed at a low irradiation dose, and a resist pattern with further improved contrast can be formed. In addition, if the number average molecular weight of copolymer B is below the upper limit value, the preparation of a positive-type resist composition becomes easier.

[0187] [Molecular Weight Distribution (Mw / Mn)]

[0188] In addition, the molecular weight distribution (Mw / Mn) of copolymer B is preferably 1.10 or higher, more preferably 1.20 or higher, preferably 1.70 or lower, and more preferably 1.65 or lower. If the molecular weight distribution (Mw / Mn) of copolymer B is above the lower limit value, the ease of manufacturing copolymer B can be increased. Furthermore, if the molecular weight distribution (Mw / Mn) of copolymer B is below the upper limit value, the contrast of the obtained resist pattern can be further increased.

[0189] [Method for preparing copolymer B]

[0190] The method for preparing copolymer B is not particularly limited. For example, copolymer B having the monomer unit (V) described above can be prepared by polymerizing a monomer composition comprising monomer (e) and any monomer copolymerizable with monomer (e), recovering the obtained copolymer, and optionally purifying it. Here, the polymerization method and the purification method are not particularly limited and can be the same as the polymerization method and purification method of copolymer A described above. In addition, when preparing copolymer B, it is preferable to use a polymerization initiator, and, for example, a polymerization initiator such as azobisisobutyronitrile may be appropriately used.

[0191] Solvent

[0192] As for the solvent, it is not particularly limited as long as it is a solvent capable of dissolving the copolymer A and copolymer B described above; for example, known solvents such as the solvent described in Japanese Patent No. 5938536 may be used. Among these, from the perspective of obtaining a positive-type resist composition with a suitable viscosity and improving the coating properties of the positive-type resist composition, it is preferable to use anisole, propylene glycol monomethyl ether acetate (PGMEA), cyclopentanone, cyclohexanone, or isoamyl acetate as the solvent.

[0193] <Preparation of a Positive-Type Resist Composition>

[0194] A positive-type resist composition can be prepared by mixing the aforementioned copolymer A, copolymer B, a solvent, and optionally known additives. At that time, in order to further reduce the reduction of the resist pattern top and simultaneously increase the contrast of the resist pattern, it is preferable that both copolymer A and copolymer B are main chain cleavage type copolymers containing halogen atoms, and more preferably, both copolymer A and copolymer B contain fluorine substituents, at least one of the halogen atoms is a fluorine atom, and said fluorine atom is included in the fluorine substituent. Furthermore, it is more preferable that either copolymer A or copolymer B has a monomer unit represented by the formula (V) described above, and more preferable that both copolymer A and copolymer B have a monomer unit represented by the formula (V) described above. In addition, particularly preferably, copolymer A has a monomer unit (I) represented by the formula (I) described above and a monomer unit (II) represented by the formula (II), and copolymer B has a monomer unit represented by the formula (III) described above and a monomer unit (IV) represented by the formula (IV). Here, in preparing the positive-type resist composition, the method of mixing the above components is not particularly limited and may be mixed by a known method. In addition, the composition may be prepared by filtering the mixture after mixing each component.

[0195] [percolation]

[0196] Here, the method of filtration of the mixture is not particularly limited and, for example, can be filtered using a filter. The filter is not particularly limited and, for example, filtration membranes such as fluorocarbon-based, cellulose-based, nylon-based, polyester-based, and hydrocarbon-based filters may be used. Among these, from the perspective of effectively preventing impurities such as metal from metal pipes used during the preparation of copolymer A and copolymer B from being incorporated into the positive-type resist composition, polyfluorocarbons such as polyethylene, polypropylene, polytetrafluoroethylene, and Teflon (registered trademark), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), nylon, and composite membranes of polyethylene and nylon are preferred as materials constituting the filter. As a filter, for example, the one disclosed in U.S. Patent No. 6103122 may be used. Additionally, commercially available filters such as Zeta Plus (registered trademark) 40Q manufactured by CUNO Incorporated may be used. In addition, the filter may comprise a strongly cationic or weakly cationic ion exchange resin. Here, the average particle size of the ion exchange resin is not particularly limited, but is preferably 2 μm or more and 10 μm or less. Examples of cation exchange resins include sulfonated phenol-formaldehyde condensates, sulfonated phenol-benzaldehyde condensates, sulfonated styrene-divinylbenzene copolymers, sulfonated methacrylic acid-divinylbenzene copolymers, and other types of polymers containing sulfonic acid or carboxylic acid groups. In the cation exchange resin, H + Counter ion, NH4 + Counterions or alkali metal counterions, e.g., K + and Na + Counter ions are provided. In addition, it is preferable that the cation exchange resin has hydrogen counter ions. As such a cation exchange resin, H +An example of a sulfonated styrene-divinylbenzene copolymer having counter ions is Purolite’s Microlite (registered trademark) PrCH. Such a cation exchange resin is commercially available as Rohm and Haas’s AMBERLYST (registered trademark).

[0197] In addition, it is preferable that the pore size of the filter be 0.001 μm or more and 1 μm or less. If the pore size of the filter is within the above range, it is possible to sufficiently prevent impurities such as metals from being incorporated into the positive-type resist composition.

[0198] <Ratio of Copolymer A to Copolymer B>

[0199] In addition, the ratio of copolymer A to copolymer B in the positive-type resist composition of the present invention is not particularly limited, but the ratio of copolymer B is preferably 1 mass% or more, more preferably 5 mass% or more, more preferably 10 mass% or more, preferably 30 mass% or less, more preferably 25 mass% or less, and more preferably 20 mass% or less. If the ratio of copolymer B is above the lower limit value, the solubility of the resist film in the developer can be suppressed to an excessively high level at a low irradiation dose, and a resist pattern with further improved contrast can be formed. Furthermore, if the ratio of copolymer B is below the upper limit value, the deterioration of the sensitivity of the positive-type resist can be suppressed.

[0200] (Resist pattern formation method)

[0201] The method for forming a resist pattern according to the present invention comprises at least a process of forming a resist film using the positive-type resist composition of the present invention described above (resist film formation process), a process of exposing the resist film to light (exposure process), and a process of developing the exposed resist film (development process).

[0202] Meanwhile, the resist pattern forming method of the present invention may further include processes other than the resist film forming process, exposure process, and development process described above. Specifically, the resist pattern forming method of the present invention may include a process of forming a lower layer film on a substrate on which the resist film is formed (lower layer forming process) before the resist film forming process. In addition, the resist pattern forming method of the present invention may include a process of heating the exposed resist film (post-exposure bake process) between the exposure process and the development process. In addition, the resist pattern forming method of the present invention may further include a process of removing the developer (rinsing process) after the development process. Furthermore, after forming the resist pattern by the resist pattern forming method of the present invention, the method may further include a process of etching the lower layer film and / or the substrate (etching process).

[0203] In addition, in the method for forming a resist pattern according to the present invention, a positive resist composition comprising a predetermined copolymer A and copolymer B is used as a positive resist composition, so the reduction of the resist pattern top is reduced and a high-contrast resist pattern can be formed.

[0204] (Resist film formation process)

[0205] In the resist film formation process, a positive-type resist composition of the present invention is applied onto a workpiece, such as a substrate, which is processed using a resist pattern, and the applied positive-type resist composition is dried to form a resist film.

[0206] -Circuit board-

[0207] Here, in the method for forming a resist pattern, the substrate capable of forming a resist film is not particularly limited and may include a substrate having an insulating layer and a copper foil formed on the insulating layer, which is used in the manufacture of printed circuit boards, etc., and mask blanks formed by forming a light-blocking layer on the substrate.

[0208] Examples of substrate materials include inorganic materials such as metal (silicon, copper, chromium, iron, aluminum, etc.), glass, titanium oxide, silicon dioxide (SiO2), silica, and mica; nitrides such as SiN; nitride oxides such as SiON; and organic materials such as acrylic, polystyrene, cellulose, cellulose acetate, and phenolic resin. Among these, metal is preferred as the substrate material. By using, for example, a silicon substrate, a silicon dioxide substrate, or a copper substrate, preferably a silicon substrate or a silicon dioxide substrate, as the substrate, a cylindrical structure can be formed.

[0209] In addition, the size and shape of the substrate are not particularly limited. Meanwhile, the surface of the substrate may be smooth, may have a curved or uneven shape, or may be a substrate with a thin sheet shape.

[0210] Additionally, surface treatment may be performed on the surface of the substrate as needed. For example, in the case of a substrate having hydroxyl groups on its surface layer, the surface of the substrate may be treated using a silane-based coupling agent capable of reacting with the hydroxyl groups. By doing so, the surface layer of the substrate can be changed from hydrophilic to hydrophobic, thereby increasing the adhesion between the substrate and the underlying film, or between the substrate and the resist layer. At this time, the silane-based coupling agent is not particularly limited, but hexamethyldisilazane is preferred.

[0211] (Sublayer formation process)

[0212] In an optional process for forming a lower layer, a lower layer is formed on a substrate. By forming a lower layer on the substrate, the surface of the substrate becomes hydrophobic. This increases the affinity between the substrate and the resist film, thereby increasing the adhesion between the substrate and the resist film. The lower layer may be an inorganic lower layer or an organic lower layer.

[0213] An inorganic underlayer can be formed by applying an inorganic material onto a substrate and performing processes such as firing. Examples of inorganic materials include silicon-based materials.

[0214] An organic underlayer can be formed by applying an organic material onto a substrate to form a film and drying it. The organic material is not limited to those sensitive to light or electron beams, and may use resist materials or resin materials commonly used in fields such as semiconductors and liquid crystals. Among these, it is preferable that the organic material be a material capable of forming an organic underlayer capable of etching, particularly dry etching. With such an organic material, the pattern of the underlayer can be formed by transferring the pattern to the underlayer by etching the organic underlayer using a pattern formed by processing a resist film. Among these, it is preferable that the organic material be a material capable of forming an organic underlayer capable of etching, such as oxygen plasma etching. Examples of organic materials used for forming the organic underlayer include AL412 from Brewer Science.

[0215] The coating of the aforementioned organic material can be performed by conventional known methods using a spin coat or a spinner. Furthermore, regarding the method for drying the coating film, any method capable of volatilizing the solvent contained in the organic material may be used, such as a baking method. At that time, the baking conditions are not particularly limited, but the baking temperature is preferably 80°C or higher and 300°C or lower, and more preferably 200°C or higher and 300°C or lower. In addition, the baking time is preferably 30 seconds or more, more preferably 60 seconds or more, preferably 500 seconds or less, more preferably 400 seconds or less, even more preferably 300 seconds or less, and particularly preferably 180 seconds or less. Furthermore, the thickness of the underlying film after drying the coating film is not particularly limited, but it is preferably 10 nm or more and 100 nm or less.

[0216] (Resist film formation process)

[0217] In the resist film formation process, a positive-type resist composition is applied to a workpiece, such as a substrate, that is processed using a resist pattern (or to the lower layer if a lower layer is formed), and the applied positive-type resist composition is dried to form a resist film.

[0218] In addition, the application and drying methods of the positive-type resist composition are not particularly limited, and methods generally used for forming resist films may be utilized. Among these, heating (pre-baking) is preferred as the drying method. Furthermore, regarding the view to improve the film density of the resist film, the pre-baking temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher. Also, regarding the view to reduce changes in the molecular weight and molecular weight distribution of copolymer A and copolymer B in the resist film before and after pre-baking, the pre-baking temperature is preferably 250°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. Furthermore, regarding the view to improve the film density of the resist film formed through pre-baking, the pre-baking time is preferably 10 seconds or longer, more preferably 20 seconds or longer, and even more preferably 30 seconds or longer. In addition, in order to further reduce changes in the molecular weight and molecular weight distribution of copolymer A and copolymer B in the resist film before and after prebaking, the prebaking time is preferably 10 minutes or less, more preferably 5 minutes or less, and even more preferably 3 minutes or less.

[0219] (Photolithography process)

[0220] In the photolithography process, an ionizing radiation such as an electron beam or EUV is irradiated onto the resist film formed in the resist film formation process to draw a desired pattern. Meanwhile, for electron beam irradiation, known drawing devices such as electron beam lithography devices or EUV lithography devices can be used.

[0221] (Post-exposure bake process)

[0222] In an optional post-exposure bake process, the resist film exposed in the exposure process is heated. By performing the post-exposure bake process, the surface roughness of the resist pattern can be reduced.

[0223] Here, the heating temperature is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, preferably 200°C or lower, more preferably 170°C or lower, and even more preferably 150°C or lower. If the heating temperature is within the above range, the surface roughness of the resist pattern can be effectively reduced while increasing the clarity of the resist pattern.

[0224] In addition, the heating time (heating time) for the resist film in the post-exposure bake process is preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 30 seconds or more. If the heating time is 10 seconds or more, the surface roughness of the resist pattern can be sufficiently reduced while further enhancing the clarity of the resist pattern. On the other hand, from the perspective of production efficiency, the heating time is preferably, for example, 10 minutes or less, more preferably 5 minutes or less, and even more preferably 3 minutes or less.

[0225] In addition, the method of heating the resist film in the post-exposure bake process is not particularly limited, and examples include heating the resist film with a hot plate, heating the resist film in an oven, or blowing hot air onto the resist film.

[0226] (Development Process)

[0227] In the development process, the exposed resist film (or the exposed and heated resist film in the case where a post-exposure bake process is performed) is developed to form a developed film on the workpiece.

[0228] Here, the development of the resist film can be performed, for example, by bringing the resist film into contact with a developer. The method of bringing the resist film into contact with the developer is not particularly limited, and known methods such as immersion of the resist film into the developer or application of the developer to the resist film may be used.

[0229] <Developer>

[0230] The developer can be appropriately selected according to the properties of copolymer A and copolymer B described above. Specifically, when selecting the developer, it is preferable to select a developer that does not dissolve the resist film before the photolithography process, while dissolving the exposed portion of the resist film after the photolithography process. In addition, one type of developer may be used alone, or two or more types may be mixed in any ratio.

[0231] And, as a developer, for example, hydrofluorocarbons such as 1,1,1,2,3,4,4,5,5,5-decafluoropentane (CF3CFHCFHCF2CF3), 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2,2,3,3,4,4-nonafluorohexane, 2,2-dichloro-1,1,1-trifluoroethane, 1,1-dichloro-1-fluoroethane, 1,1-dichloro-2,2,3,3,3-pentafluoropropane (CF3CF2CHCl2), Hydrochlorofluorocarbons such as 1,3-dichloro-1,1,2,2,3-pentafluoropropane (CClF2CF2CHClF), hydrofluoroethers such as methylnonafluorobutyl ether (CF3CF2CF2CF2OCH3), methylnonafluoroisobutyl ether, ethylnonafluorobutyl ether (CF3CF2CF2CF2OC2H5), ethylnonafluoroisobutyl ether, and perfluorohexylmethyl ether (CF3CF2CF(OCH3)C3F7), and CF4, C2F6, C3F8, C4F8, C4F 10 , C5F 12 , C6F12 , C6F 14 , C7F 14 , C7F 16 , C8F 18 , C9F 20 Fluorinated solvents such as perfluorocarbons; alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol; acetic acid esters having alkyl groups such as amyl acetate and hexyl acetate; mixtures of fluorinated solvents and alcohols; mixtures of fluorinated solvents and acetic acid esters having alkyl groups; mixtures of alcohols and acetic acid esters having alkyl groups; mixtures of fluorinated solvents and alcohols and acetic acid esters having alkyl groups; etc., may be used. Among these, from the perspective of further enhancing the contrast of the resist pattern, it is preferable to develop using alcohols such as 2-butanol and isopropyl alcohol.

[0232] Meanwhile, the temperature of the developing solution during development is not specifically limited, but can be, for example, 5°C or higher and 40°C or lower. In addition, the development time can be, for example, 10 seconds or higher and 4 minutes or lower.

[0233] (Rinsing process)

[0234] In the resist pattern forming method of the present invention, a process of removing the developer solution can be performed after the development process. The removal of the developer solution can be performed, for example, using a rinse solution.

[0235] Specific examples of the rinse solution include, for instance, hydrocarbon-based solvents such as octane and heptane, or water, in addition to the developer solution exemplified in the section on the "development process." Here, the rinse solution may contain a surfactant. Furthermore, when selecting the rinse solution, it is preferable to select a rinse solution that is less likely to dissolve the resist film before the photolithography process than the developer solution used in the development process, and is also easier to mix with the developer solution.

[0236] Meanwhile, the temperature of the rinse solution during rinsing is not specifically limited, but can be, for example, 5°C or higher and 40°C or lower. In addition, the rinsing time can be, for example, 5 seconds or higher and 3 minutes or lower.

[0237] The above-described developer and rinse solutions may each be filtered before use. As for the filtration method, for example, the filtration method using a filter described in the above-described section "Preparation of a positive-type resist composition" may be cited.

[0238] (Etching process)

[0239] In an etching process that can be optionally performed, the lower layer film and / or substrate are etched using the above-described resist pattern as a mask to form a pattern on the lower layer film and / or substrate.

[0240] At that time, the number of etching cycles is not particularly limited and may be one or multiple. In addition, the etching may be dry etching or wet etching, but dry etching is preferred. Dry etching can be performed using a known dry etching apparatus. The etching gas used for dry etching can be appropriately selected according to the elemental composition of the underlying film or substrate to be etched. As etching gases, for example, fluorine-based gases such as CHF3, CF4, C2F6, C3F8, SF6; chlorine-based gases such as Cl2, BCl3; oxygen-based gases such as O2, O3, H2O; reducing gases such as H2, NH3, CO, CO2, CH4, C2H2, C2H4, C2H6, C3H4, C3H6, C3H8, HF, HI, HBr, HCl, NO, BCl3; Examples include inert gases such as He, N2, and Ar. These gases may be used individually or in a mixture of two or more types. Meanwhile, oxygen-based gases are typically used for the dry etching of inorganic underlying films. Additionally, fluorine-based gases are typically used for the dry etching of substrates, and a mixture of fluorine-based gases and inert gases is suitable for use.

[0241] Additionally, if necessary, the underlying layer remaining on the substrate may be removed before or after etching the substrate. When removing the underlying layer before etching the substrate, the underlying layer may be a patterned underlying layer or an unpatterned underlying layer.

[0242] Here, methods for removing the lower film include, for example, the dry etching described above. In addition, in the case of an inorganic lower film, the lower film may be removed by contacting the lower film with a liquid such as a basic solution or an acidic solution, preferably a basic liquid. Here, the basic solution is not particularly limited and may include, for example, alkaline hydrogen peroxide. A method for removing the lower film by wet stripping using alkaline hydrogen peroxide is not particularly limited as long as the lower film and the alkaline hydrogen peroxide can come into contact for a certain period of time under heating conditions, and may include, for example, a method of immersing the lower film in heated alkaline hydrogen peroxide, a method of spraying alkaline hydrogen peroxide onto the lower film under a heating environment, or a method of coating the lower film with heated alkaline hydrogen peroxide. After performing any one of these methods, the substrate can be washed with water and dried to obtain a substrate from which the lower film has been removed.

[0243] Hereinafter, an example of a method for forming a resist pattern using a positive-type resist of the present invention and a method for etching a lower layer film and a substrate using the formed resist pattern will be described. However, since the substrate and conditions in each process used in the following example can be the same as those described above regarding the substrate and conditions in each process, the description below will be omitted. Meanwhile, the method for forming a resist pattern of the present invention is not limited to the method shown in the following example.

[0244] An example of a resist pattern formation method is a resist pattern formation method using an electron beam or EUV, comprising the above-described lower layer formation process, resist film formation process, exposure process, development process, and rinsing process. Additionally, an example of an etching method is to use the resist pattern formed by the resist pattern formation method as a mask, and includes an etching process.

[0245] Specifically, in the process of forming a lower layer, an inorganic lower layer is formed by applying an inorganic material onto a substrate and performing firing.

[0246] Next, in the resist film formation process, the positive-type resist composition of the present invention is applied to the inorganic lower film formed in the lower film formation process and dried to form a resist film.

[0247] Then, in the photolithography process, EUV is irradiated onto the resist film formed in the resist film formation process to draw a desired pattern.

[0248] In addition, in the development process, the resist film exposed in the photolithography process is brought into contact with the developer to develop the resist film, thereby forming a resist pattern on the lower layer.

[0249] And, in the rinsing process, the developed resist film from the developing process is brought into contact with the rinsing liquid to rinse the developed resist film.

[0250] Then, in the etching process, the lower layer is etched using the resist pattern as a mask to form a pattern on the lower layer.

[0251] Next, the substrate is etched using the patterned lower layer film as a mask to form a pattern on the substrate.

[0252] (Etching resistance of the resist film)

[0253] The resist film obtained by the resist pattern forming method of the present invention has excellent etching resistance, and in particular, excellent dry etching resistance. Meanwhile, the higher the ratio of carbon content per unit volume of copolymer A and copolymer B included in the positive type resist composition, the more the resist film tends to have excellent dry etching resistance.

[0254] And, according to the resist pattern forming method of the present invention, a laminate having a resist film having a two-layer structure as described below, for example, can be obtained.

[0255] (Laminate)

[0256] A laminate obtained by the method for forming a resist pattern of the present invention comprises a substrate and a resist film formed on the substrate, wherein the resist film comprises a lower layer formed on the substrate and an upper layer formed on the lower layer. Furthermore, the lower layer is composed of the copolymer A described above, and the upper layer is composed of the copolymer B described above. The resist film provided by the laminate of the present invention can be formed by the method for forming a resist pattern of the present invention.

[0257] Examples

[0258] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0259] Meanwhile, in the examples and comparative examples, the number average molecular weight, weight average molecular weight, and molecular weight distribution of the copolymer were measured by the following method.

[0260] Number Average Molecular Weight, Weight Average Molecular Weight, and Molecular Weight Distribution

[0261] For the obtained copolymer A and copolymer B, the number average molecular weight (Mn) and weight average molecular weight (Mw) were measured using gel permeation chromatography, and the molecular weight distribution (Mw / Mn) was calculated.

[0262] Specifically, a gel permeation chromatograph (manufactured by Tosoh, HLC-8220) was used, and tetrahydrofuran was used as the developing solvent to determine the number average molecular weight (Mn) and weight average molecular weight (Mw) of the copolymer as standard polystyrene equivalents. Then, the molecular weight distribution (Mw / Mn) was calculated. Meanwhile, it was confirmed that each of the obtained copolymers A and B substantially did not contain any component with a weight average molecular weight (Mw) of less than 1000.

[0263] <Preparation of Copolymer A>

[0264] <<Preparation Example 1: Preparation of Copolymer A1>>

[0265] [Synthesis of Polymers]

[0266] A monomer composition comprising 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a), 2.493 g of α-methylstyrene as monomer (b), and 2.833 g of cyclopentanone as solvent was added to a glass ampoule containing a stirrer, sealed, and the oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0267] Then, the system was heated to 30°C and the reaction was carried out for 80 hours. Next, 10 g of tetrahydrofuran (THF) was added to the system, and the resulting solution was added dropwise to 100 g of methanol (MeOH) as a solvent to precipitate a polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units.

[0268] Afterwards, the number average molecular weight, weight average molecular weight, and molecular weight distribution were measured for the obtained copolymer (copolymer A1 before purification). The results are shown in Table 1.

[0269] [Purification of Polymers]

[0270] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 29:71) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units).

[0271] Afterwards, the number average molecular weight, weight average molecular weight, and molecular weight distribution were measured for the obtained copolymer (copolymer A1 after purification). The results are shown in Table 1.

[0272] <<Preparation Example 2: Preparation of Copolymer A2>>

[0273] [Preparation of an aqueous solution with 18% solid content of semi-cured beef tallow fatty acid potassium soap]

[0274] 100 g of ion-exchanged water was prepared and heated to 70°C while stirring, and 8.40 g of potassium hydroxide (49% aqueous solution) was added. Next, 19.6 g of beef tallow 45° hardened fatty acid HFA (manufactured by Nichiyu Co., Ltd.) was added at an addition rate of 1.28 g / min, and then 0.126 g of potassium silicate was added. The mixture was then stirred at 80°C for more than 2 hours to obtain an aqueous solution of semi-hardened beef tallow fatty acid potassium soap with a solid content of 18%.

[0275] [Synthesis of Polymers]

[0276] 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a) and 2.712 g of α-methylstyrene as monomer (b) were added to a glass ampoule containing a stirrer. Additionally, 6.771 g of ion-exchanged water was added to 0.5463 g of an aqueous solution of 18% solid content of the semi-cured beef tallow fatty acid potassium soap prepared above to form a monomer composition, the ampoule was sealed, and oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0277] Then, the system was heated to 40°C, and the polymerization reaction was carried out for 11 hours. Next, 10 g of THF was added to the system, and the resulting solution was added dropwise to 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units.

[0278] Afterwards, various measurements were performed on the obtained copolymer (copolymer A2 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0279] [Purification of Polymers]

[0280] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 35:65) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units).

[0281] Afterwards, various measurements were performed on the obtained copolymer (copolymer A2 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0282] <<Preparation Example 3: Preparation of Copolymer A3>>

[0283] [Synthesis of Polymers]

[0284] A monomer composition comprising 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a), 1.066 g of α-methylstyrene as monomer (b), and 1.743 g of cyclopentanone as solvent was added to a glass ampoule containing a stirrer, sealed, and oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0285] Then, the system was heated to 30°C and the reaction was carried out for 50 hours. Next, 10 g of tetrahydrofuran was added to the system, and the resulting solution was added dropwise to 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units.

[0286] Afterwards, various measurements were performed on the obtained copolymer (copolymer A3 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0287] [Purification of Polymers]

[0288] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 30:70) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered using a Kiriyama funnel to obtain a white copolymer (a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units).

[0289] Afterwards, various measurements were performed on the obtained copolymer (copolymer A3 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0290] <<Preparation Example 4: Preparation of Copolymer A4>>

[0291] [Synthesis of Polymers]

[0292] 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a) and 1.066 g of α-methylstyrene as monomer (b) were added to a glass ampoule containing a stirrer. Additionally, 6.771 g of ion-exchanged water was added to 0.5463 g of an aqueous solution of 18% solid content of semi-cured beef tallow fatty acid potassium soap prepared in Preparation Example 2 to form a monomer composition, and then the ampoule was sealed and the oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0293] Then, the system was heated to 75°C and the polymerization reaction was carried out for 1 hour. Next, 10 g of tetrahydrofuran was added to the system, and the resulting solution was dropped into 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 30:70) to precipitate the polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units.

[0294] Afterwards, various measurements were performed on the obtained copolymer (copolymer A4 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0295] [Purification of Polymers]

[0296] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 34:66) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered using a Kiriyama funnel to obtain a white copolymer (a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units).

[0297] Afterwards, various measurements were performed on the obtained copolymer (copolymer A4 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0298] <<Preparation Example 5: Preparation of Copolymer A5>>

[0299] [Synthesis of Polymers]

[0300] A copolymer (copolymer A5 before purification) was obtained by performing the same operation as in Preparation Example 4, except that the mass ratio of THF and MeOH in the mixed solvent used for polymer precipitation during the synthesis of the polymer was changed to 33:67.

[0301] Afterwards, various measurements were performed on the obtained copolymer (copolymer A5 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0302] [Purification of Polymers]

[0303] A copolymer was obtained by performing the same operation as in Preparation Example 4, except that the mass ratio of THF and MeOH in the mixed solvent used for purifying the polymer was changed to 33:67 and purification was performed twice.

[0304] Afterwards, various measurements were performed on the obtained copolymer (copolymer A5 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0305] <<Preparation Example 6: Preparation of Copolymer A6>>

[0306] [Synthesis of Polymers]

[0307] 3 g of α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPhOMe) as monomer (a) and 2.487 g of α-methylstyrene as monomer (b) were added to a glass ampoule containing a stirrer. Additionally, 6.771 g of ion-exchanged water was added to 0.5463 g of an aqueous solution of 18% solid content of semi-cured beef tallow fatty acid potassium soap prepared in Preparation Example 2 to form a monomer composition, and then the ampoule was sealed and the oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0308] Then, the system was heated to 75°C and the polymerization reaction was carried out for 1 hour. Next, 10 g of tetrahydrofuran was added to the system, and the resulting solution was added dropwise to 100 g of methanol as a solvent to precipitate the polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units.

[0309] Afterwards, various measurements were performed on the obtained copolymer (copolymer A6 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0310] [Purification of Polymers]

[0311] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 30:70) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered using a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units).

[0312] Afterwards, various measurements were performed on the obtained copolymer (copolymer A6 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0313] <<Preparation Example 7: Preparation of Copolymer A7>>

[0314] [Synthesis of Polymers]

[0315] 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (a) and 1.066 g of α-methylstyrene as monomer (b) were added to a glass ampoule containing a stirrer. Additionally, 6.771 g of ion-exchanged water was added to 0.5463 g of an aqueous solution of 18% solid content of semi-cured beef tallow fatty acid potassium soap prepared in Preparation Example 2 to form a monomer composition, and then the ampoule was sealed and the oxygen in the system was removed by repeating pressurization and depressurization with nitrogen gas 10 times.

[0316] Then, the system was heated to 40°C, and the polymerization reaction was carried out for 11 hours. Next, 10 g of tetrahydrofuran was added to the system, and the resulting solution was added dropwise to 100 g of methanol as a solvent to precipitate the polymer. Afterward, the precipitated polymer was recovered by filtration. Meanwhile, the obtained polymer was a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units.

[0317] Afterwards, various measurements were performed on the obtained copolymer (copolymer A7 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0318] [Purification of Polymers]

[0319] The polymer recovered by filtration was dissolved in 10 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 34:66) to precipitate a white coagulated product (a copolymer containing α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated copolymer was filtered using a Kiriyama funnel to obtain a white copolymer (a copolymer containing 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units).

[0320] Afterwards, various measurements were performed on the obtained copolymer (copolymer A7 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 1.

[0321] <Preparation of Copolymer B>

[0322] <<Preparation Example 8: Preparation of Copolymer B1>>

[0323] [Synthesis of Polymers]

[0324] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.476 g of α-methylstyrene as monomer (d), 0.0055 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0325] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units.

[0326] Afterwards, various measurements were performed on the obtained copolymer (copolymer B1 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0327] [Purification of Polymers]

[0328] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 15:85) to precipitate a white coagulated product (a copolymer containing 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units).

[0329] Afterwards, various measurements were performed on the obtained copolymer (copolymer B1 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0330] <<Preparation Example 9: Preparation of Copolymer B2>>

[0331] [Synthesis of Polymers]

[0332] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.468 g of α-methylstyrene as monomer (d), 0.0014 g of azobisisobutyronitrile as a polymerization initiator, and 6.4666 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 50 hours in a constant temperature bath at 40°C under a nitrogen atmosphere.

[0333] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units.

[0334] Afterwards, various measurements were performed on the obtained copolymer (copolymer B2 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0335] [Purification of Polymers]

[0336] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 26:74) to precipitate a white coagulated product (a polymer containing 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units).

[0337] Afterwards, various measurements were performed on the obtained copolymer (copolymer B2 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0338] <<Preparation Example 10: Preparation of Copolymer B3>>

[0339] [Synthesis of Polymers]

[0340] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.476 g of α-methylstyrene as monomer (d), 0.1103 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0341] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units.

[0342] Afterwards, various measurements were performed on the obtained copolymer (copolymer B3 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0343] [Purification of Polymers]

[0344] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 5:95) to precipitate a white coagulated product (a copolymer containing 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3-pentafluoropropyl units of α-chloroacrylic acid and α-methylstyrene units).

[0345] Afterwards, various measurements were performed on the obtained copolymer (copolymer B3 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0346] <<Preparation Example 11: Preparation of Copolymer B4>>

[0347] [Synthesis of Polymers]

[0348] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.476 g of α-methylstyrene as monomer (d), 0.0005 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and the mixture was stirred for 2 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0349] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units.

[0350] Afterwards, various measurements were performed on the obtained copolymer (copolymer B4 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0351] [Purification of Polymers]

[0352] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 20:80) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units).

[0353] Afterwards, various measurements were performed on the obtained copolymer (copolymer B4 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0354] <<Preparation Example 12: Preparation of Copolymer B5>>

[0355] [Synthesis of Polymers]

[0356] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.476 g of α-methylstyrene as monomer (d), 0.0275 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0357] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units.

[0358] Afterwards, various measurements were performed on the obtained copolymer (copolymer B5 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0359] [Purification of Polymers]

[0360] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 10:90) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units).

[0361] Afterwards, various measurements were performed on the obtained copolymer (copolymer B5 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0362] <<Preparation Example 13: Preparation of Copolymer B6>>

[0363] [Synthesis of Polymers]

[0364] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (c), 3.235 g of 4-fluoro-α-methylstyrene as monomer (d), 0.0014 g of azobisisobutyronitrile as a polymerization initiator, and 6.4666 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 50 hours in a constant temperature bath at 40°C under a nitrogen atmosphere.

[0365] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units.

[0366] Afterwards, various measurements were performed on the obtained copolymer (copolymer B6 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0367] [Purification of Polymers]

[0368] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 25:75) to precipitate a white coagulated product (a copolymer containing 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3,3-pentafluoropropyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units).

[0369] Afterwards, various measurements were performed on the obtained copolymer (copolymer B6 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0370] <<Preparation Example 14: Preparation of Copolymer B7>>

[0371] [Synthesis of Polymers]

[0372] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,2-trifluoroethyl (ACATFE) as monomer (c), 4.399 g of α-methylstyrene as monomer (d), 0.0070 g of azobisisobutyronitrile as a polymerization initiator, and 1.8514 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0373] Afterward, the solution was returned to room temperature and the inside of the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was added dropwise to 100 g of MeOH as a solvent to precipitate a polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,2-trifluoroethyl units and α-methylstyrene units.

[0374] Afterwards, various measurements were performed on the obtained copolymer (copolymer B7 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0375] [Purification of Polymers]

[0376] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 15:85) to precipitate a white coagulated product (a copolymer containing 50% each of α-chloroacrylic acid 2,2,2-trifluoroethyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,2-trifluoroethyl units and α-methylstyrene units).

[0377] Afterwards, various measurements were performed on the obtained copolymer (copolymer B7 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 2.

[0378] <<Preparation Example 15: Preparation of Copolymer B8>>

[0379] [Synthesis of Polymers]

[0380] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 2.8783 g of α-methylstyrene as monomer (d), 0.0046 g of azobisisobutyronitrile as a polymerization initiator, and 1.471 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 50 hours in a constant temperature bath at 40°C under a nitrogen atmosphere.

[0381] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units.

[0382] Afterwards, various measurements were performed on the obtained copolymer (copolymer B8 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0383] [Purification of Polymers]

[0384] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 20:80) to precipitate a white coagulated product (a copolymer containing 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units).

[0385] Afterwards, various measurements were performed on the obtained copolymer (copolymer B8 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0386] <<Preparation Example 16: Preparation of Copolymer B9>>

[0387] [Synthesis of Polymers]

[0388] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 2.8783 g of α-methylstyrene as monomer (d), 0.0046 g of azobisisobutyronitrile as a polymerization initiator, and 1.471 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0389] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units.

[0390] Afterwards, various measurements were performed on the obtained copolymer (copolymer B9 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0391] [Purification of Polymers]

[0392] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 10:90) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units).

[0393] Afterwards, various measurements were performed on the obtained copolymer (copolymer B9 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0394] <<Preparation Example 17: Preparation of Copolymer B10>>

[0395] [Synthesis of Polymers]

[0396] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 2.8783 g of α-methylstyrene as monomer (d), 0.0046 g of azobisisobutyronitrile as a polymerization initiator, and 1.4813 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0397] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units.

[0398] Afterwards, various measurements were performed on the obtained copolymer (copolymer B10 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0399] [Purification of Polymers]

[0400] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 9:91) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units).

[0401] Afterwards, various measurements were performed on the obtained copolymer (copolymer B10 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0402] <<Preparation Example 18: Preparation of Copolymer B11>>

[0403] [Synthesis of Polymers]

[0404] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 2.8783 g of α-methylstyrene as monomer (d), 0.0913 g of azobisisobutyronitrile as a polymerization initiator, and 1.4927 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0405] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units.

[0406] Afterwards, various measurements were performed on the obtained copolymer (copolymer B11 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0407] [Purification of Polymers]

[0408] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 7:93) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units).

[0409] Afterwards, various measurements were performed on the obtained copolymer (copolymer B11 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0410] <<Preparation Example 19: Preparation of Copolymer B12>>

[0411] [Synthesis of Polymers]

[0412] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 2.8783 g of α-methylstyrene as monomer (d), 0.1827 g of azobisisobutyronitrile as a polymerization initiator, and 1.5155 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0413] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and α-methylstyrene units.

[0414] Afterwards, various measurements were performed on the obtained copolymer (copolymer B12 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0415] [Purification of Polymers]

[0416] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 4:96) to precipitate a white coagulated product (a copolymer containing 50 mol% each of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a polymer containing α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl units and α-methylstyrene units).

[0417] Afterwards, various measurements were performed on the obtained copolymer (copolymer B12 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0418] <<Preparation Example 20: Preparation of Copolymer B13>>

[0419] [Synthesis of Polymers]

[0420] A monomer composition comprising 3 g of α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl (ACAHFB) as monomer (c), 3.315 g of 4-fluoro-α-methylstyrene as monomer (d), 0.0457 g of azobisisobutyronitrile as a polymerization initiator, and 1.5902 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and nitrogen-substituted, and stirred for 6 hours in a constant temperature bath at 78°C under a nitrogen atmosphere.

[0421] Afterward, the solution was returned to room temperature and the glass container was exposed to the atmosphere, and 10 g of THF was added to the obtained solution. Then, the solution with added THF was dropped into 100 g of MeOH as a solvent to precipitate the polymer. Afterward, the solution containing the precipitated polymer was filtered through a Kiriyama funnel to obtain a white coagulated product (polymer). Meanwhile, the obtained polymer was a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units.

[0422] Afterwards, various measurements were performed on the obtained copolymer (copolymer B13 before purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0423] [Purification of Polymers]

[0424] Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was added dropwise to 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 8:92) to precipitate a white coagulated product (a copolymer containing 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units). Subsequently, the solution containing the precipitated coagulated product was filtered through a Kiriyama funnel to obtain a white copolymer (a copolymer containing 50 mol% each of 2,2,3,3,4,4,4-heptafluorobutyl units of α-chloroacrylic acid and 4-fluoro-α-methylstyrene units).

[0425] Afterwards, various measurements were performed on the obtained copolymer (copolymer B13 after purification) in the same manner as in Preparation Example 1. The results are shown in Table 3.

[0426] (Example 1)

[0427] <Preparation of a Positive-Type Resist Composition>

[0428] A positive-type resist composition comprising only copolymer A was prepared by dissolving copolymer A1, prepared as described above, in isoamyl acetate as a solvent to prepare a positive-type resist composition (A) with a concentration of 3 mass%.

[0429] In addition, as a positive type resist composition containing only copolymer B, copolymer B1 prepared as described above was dissolved in isoamyl acetate as a solvent to prepare a positive type resist composition (B) with a concentration of 3 mass%.

[0430] In addition, as a positive type resist composition comprising copolymer A and copolymer B, copolymer A1 prepared as described above and copolymer B1 prepared as described above were dissolved in isoamyl acetate as a solvent such that the mass ratio of copolymer A1 to copolymer B1 was 99:1, thereby preparing a positive type resist composition (A·B mixed system) with a concentration of 3 mass%.

[0431] <γ value>

[0432] Using a spin coater (Mikasa, MS-A150), the positive-type resist composition (A·B mixed system) obtained as described above was applied to a silicon wafer with a diameter of 4 inches to a thickness of 50 nm. Then, the applied positive-type resist composition (A·B mixed system) was heated on a hot plate at a temperature of 170°C for 1 minute to form a resist film on the silicon wafer (resist film formation process). Then, using an electron beam lithography device (ELIONIX, ELS-S50), multiple patterns (dimensions 500 μm × 500 μm) with different electron beam irradiation doses were lithographed onto the resist film (exposure process), and the resist film after exposure was heated on a hot plate at 100°C for 1 minute (post-exposure bake process). For the resist film after heating, isopropyl alcohol was used as the developer and a development treatment was performed at a temperature of 23°C for 1 minute (development process). Afterwards, the developer was removed by nitrogen blowing.

[0433] Meanwhile, the electron beam irradiation dose is 4 μC / cm² 2 to 200 μC / cm 2 Within the range of 4 μC / cm 2 Next, the thickness of the resist film in the drawn area was measured using an optical film thickness meter (manufactured by SCREEN Semiconductor Solution, Lambda Ace), and a sensitivity curve was created showing the relationship between the common logarithm of the total electron beam irradiation dose and the residual film ratio of the resist film after development (= film thickness of the resist film after development / film thickness of the resist film formed on the silicon wafer).

[0434] Then, for the obtained sensitivity curve (horizontal axis: common logarithm of the total electron beam irradiation dose, vertical axis: residual film rate of the resist film (0 ≤ residual film rate ≤ 1.00)), the sensitivity curve was fitted to a quadratic function in the range of residual film rates from 0.20 to 0.80, and a straight line (an approximation of the slope of the sensitivity curve) connecting the point at a residual film rate of 0 and the point at a residual film rate of 0.50 was constructed on the obtained quadratic function (a function of the residual film rate and the common logarithm of the total irradiation dose). In addition, the total electron beam irradiation dose E at which the residual film rate becomes 0 on the obtained straight line (a function of the residual film rate and the common logarithm of the total irradiation dose) th (μC / cm 2 ) was calculated. Meanwhile, E th The smaller the value of , the higher the sensitivity, and it indicates that copolymer A and copolymer B as positive resists can be cut well with a small amount of irradiation.

[0435] In addition, the value of γ was calculated using the following equation. The results are shown in Table 4. Meanwhile, among the following equations, E0 is the logarithm of the total irradiation dose obtained by fitting the sensitivity curve to a quadratic function in the range of a residual film rate of 0.20 to 0.80 and substituting a residual film rate of 0 into the obtained quadratic function (a function of the residual film rate and the common logarithm of the total irradiation dose). Also, E1 is the logarithm of the total irradiation dose obtained by drawing a straight line (an approximation line of the slope of the sensitivity curve) connecting the point of a residual film rate of 0 and the point of a residual film rate of 0.50 on the obtained quadratic function and substituting a residual film rate of 1.00 into the obtained straight line (a function of the residual film rate and the common logarithm of the total irradiation dose). Furthermore, the following equation represents the slope of the above straight line between a residual film rate of 0 and 1.00. Meanwhile, it indicates that the larger the value of γ, the steeper the slope of the sensitivity curve, and the better a clear pattern can be formed.

[0436] [Mathematical Formula 1]

[0437]

[0438] <eth>

[0439] A resist film was formed on a silicon wafer using the same evaluation method as for the "γ value." The initial thickness T0 of the obtained resist film was measured using an optical film thickness gauge (manufactured by SCREEN Semiconductor Solutions, Lambda Ace). In addition, the total electron beam irradiation dose Eth (μC / cm²) at which the residual film rate of the straight line (approximately the slope of the sensitivity curve) obtained during the calculation of the γ value becomes zero was 2 ) was calculated. The results are shown in Table 4. A smaller value of Eth indicates higher sensitivity of the resist film and higher efficiency in forming the resist pattern.

[0440] <Residual Film Rate (Half Pitch (hp): 25 nm)>

[0441] Using a spin coater (Mikasa, MS-A150), the positive-type resist composition (A·B mixed system) obtained as described above was applied to a 4-inch silicon wafer to a thickness of 50 nm. Then, the applied positive-type resist composition was heated on a hot plate at a temperature of 170°C for 1 minute to form a positive-type resist film on the silicon wafer. Subsequently, using an electron beam lithography device (ELIONIX, ELS-S50), a line-and-space 1:1 pattern with a line width of 25 nm (i.e., half-pitch 25 nm) was formed with an optimal exposure amount (E op Each was electron beam lithographed using ), and electron beam lithographed wafers were obtained. Meanwhile, the optimal exposure amount was E, respectively. th It was set appropriately based on a value approximately twice that of.

[0442] The electron beam lithography-completed wafer was subjected to a development treatment by immersing it in isopropyl alcohol (IPA), used as a resist developer, for 1 minute at 23°C. Subsequently, the developer was removed by nitrogen blowing to form a line-and-space pattern (half pitch: 25 nm). Afterward, the patterned portion was cleaved, and observation was performed at a magnification of 100,000x using a scanning electron microscope (JMS-7800F PRIME, manufactured by Nippon Electronics Co., Ltd.), and the maximum height (T) of the resist pattern after development was max The initial thickness T0 of the resist film and the ) was measured. Then, the "residual film ratio (half pitch (hp): 25 nm)" was calculated using the following formula and evaluated based on the following criteria. The results are shown in Table 4. A higher residual film ratio (half pitch (hp): 25 nm) indicates less reduction of the resist pattern top.

[0443] Residual film percentage (%) = (T max / T0) × 100

[0444] A exceeding 98.5%

[0445] B Over 96% 98.5% or less

[0446] C 96% or less

[0447] Remnants

[0448] Regarding the resist pattern formed during the evaluation of the aforementioned <residual film rate>, a scanning electron microscope (SEM) was used to observe the pattern at a magnification of 100,000x, and the extent of residual material remaining in the resist pattern was evaluated according to the following criteria. The results are shown in Table 4. Meanwhile, residual material remaining within the resist pattern can be identified as high-intensity "dots" in the SEM image compared to the line pattern area without attached residue. The less residual material there is within the resist pattern, the higher the contrast of the resist pattern.

[0449] A: No residue is detected within the hp 25 nm resist pattern.

[0450] B: There is extremely small residue within the hp 25 nm resist pattern, but it is within the acceptable range.

[0451] C: A large amount of residue was found within the hp 25 nm resist pattern, which is outside the acceptable range.

[0452] Dry Etching Resistance

[0453] Using a spin coater (Mikasa, MS-A150), the positive-type resist composition (A·B mixed system) obtained as described above was applied to a silicon wafer with a diameter of 4 inches to a thickness of 500 nm. Then, the applied positive-type resist composition was heated on a hot plate at a temperature of 170°C for 1 minute to form a resist film on the silicon wafer.

[0454] Next, the resist film was etched using a plasma etching device (manufactured by Shinko Seiki Co., Ltd., EXAM) (gas type: CF4, flow rate: 100 sccm, pressure: 10 Pa, power consumption: 200 W). Afterward, the time until the film thickness was completely lost was calculated using a step, surface roughness, and micro-shape measuring device (manufactured by KLA Tencor Co., Ltd., P6). Then, the dry etching resistance was evaluated according to the following criteria. The results are shown in Table 4. Meanwhile, the longer the time until the film is completely lost (etching time), the better the dry etching resistance.

[0455] A: The time for membrane disappearance is 4 minutes and 40 seconds or more

[0456] B: Time for membrane loss is 4 minutes or more and less than 4 minutes 40 seconds

[0457] C: Time for membrane loss is less than 4 minutes

[0458] <Difference in surface free energy between copolymer A and copolymer B, surface free energy of the mixed system of copolymer A and copolymer B>

[0459] A film (membrane) was prepared using each of the positive resist composition (A), positive resist composition (B), and positive resist composition (A·B mixed system) prepared as described above, by the following method. Next, for the obtained film (membrane), the contact angle of two types of solvents (water and diiodomethane) with known surface tension, polarity term (p), and dispersion force term (d) was measured under the following conditions using a contact angle meter (Kyowa Interface Science, Drop Master 700), and the surface free energy was evaluated by the Owens-Wendt (extended Fowkes) method to calculate the surface free energy of the film (membrane).

[0460] Then, the surface free energy of the film (membrane) produced using the positive-type resist composition (A) was set as the "surface free energy of copolymer A," and the surface free energy of the film (membrane) produced using the positive-type resist composition (B) was set as the "surface free energy of copolymer B," and the difference between the surface free energy of copolymer A and the surface free energy of copolymer B (= "surface free energy of copolymer A" - "surface free energy of copolymer B") was calculated.

[0461] In addition, the surface free energy of a film (membrane) produced using a positive-type resist composition (A·B mixed system) was defined as the "surface free energy of the mixed system of copolymer A and copolymer B." The results are shown in Tables 1, 2, and 4.

[0462] <<Method of producing film (membrane)>>

[0463] A positive resist composition was applied to a silicon wafer with a diameter of 4 inches to a thickness of 50 nm using a spin coater (Mikasa, MS-A150). Then, the applied positive resist composition was heated on a hot plate at a temperature of 170°C for 1 minute to form a resist film on the silicon wafer.

[0464] <<Measurement Conditions for Contact Angle Measurement>>

[0465] Needle: Metal needle 22 G (water), Teflon (registered trademark) coated 22 G (diiodomethane)

[0466] Waiting time: 1000 ms

[0467] Liquid volume: 1.8 μL

[0468] Liquid recognition: Water 50 dat, Diiodomethane 100 dat

[0469] Temperature: 23℃

[0470] (Examples 2–64)

[0471] A positive-type resist composition was prepared in the same manner as in Example 1, except that the types of copolymer A and copolymer B and the mass ratio of copolymer A and copolymer B were changed as shown in Tables 4 to 9.

[0472] Using the obtained positive-type resist composition, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Tables 4 to 9.

[0473] (Examples 65-67)

[0474] A resist film was formed in the same manner as in Example 1, except that the type of copolymer A and the mass ratio of copolymer A to copolymer B were changed as shown in Table 9 and the post-exposure bake process was not performed.

[0475] Various measurements and evaluations were performed using the obtained resist film in the same manner as in Example 1. The results are shown in Table 9.

[0476] (Examples 68~84)

[0477] A positive resist composition was prepared in the same manner as in Example 1, except that the types of copolymer A and copolymer B and the mass ratio of copolymer A and copolymer B were changed as shown in Table 10, and ethanol (EtOH) was used instead of isopropyl alcohol as the developer.

[0478] Using the obtained positive-type resist composition, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 10.

[0479] (Examples 85–93)

[0480] A positive-type resist composition was prepared in the same manner as in Example 1, except that the types of copolymer A and copolymer B, the mass ratio of copolymer A and copolymer B, and the developer were changed as shown in Table 11.

[0481] Using the obtained positive-type resist composition, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 11.

[0482] (Comparative Examples 1–18)

[0483] A positive-type resist composition was prepared in the same manner as in Example 1, except that the types of copolymer A and copolymer B and the mass ratio of copolymer A and copolymer B were changed as shown in Table 12.

[0484] Using the obtained positive-type resist composition, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 12.

[0485] (Comparative Examples 19~24)

[0486] A positive-type resist composition was prepared in the same manner as in Example 1, except that copolymer A was not used and the developer was changed as shown in Table 13.

[0487] Using the obtained positive-type resist composition, various measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 13.

[0488] Meanwhile, among the tables,

[0489] "ACAFPh" represents α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl, and

[0490] "ACAFPhOMe" represents α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl, and

[0491] "KORR(18%) soap" refers to an aqueous solution of semi-cured beef tallow fatty acid potassium soap with a solid content of 18%, and

[0492] "ACAPFP" represents α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl, and

[0493] "ACAHFB" represents α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl, and

[0494] "ACATFE" represents α-chloroacrylic acid 2,2,2-trifluoroethyl, and

[0495] "IPA" represents isopropyl alcohol,

[0496] "EtOH" represents ethanol,

[0497] "PrOH" represents 1-propanol, and

[0498] "ButOH" represents 1-butanol.

[0499]

[0500]

[0501]

[0502]

[0503]

[0504]

[0505]

[0506]

[0507]

[0508]

[0509]

[0510]

[0511]

[0512] From Tables 4 to 11, it can be seen that in Examples 1 to 93, in which a predetermined positive-type resist composition containing copolymer A and copolymer B was used as a positive-type resist composition, the reduction of the resist pattern top was small and a resist pattern with high contrast could be formed.

[0513] Meanwhile, from Tables 12 and 13, it can be seen that when a positive-type resist composition containing only one of copolymer A and copolymer B was used (Comparative Examples 1-5, 7, 9, 11, 13, 15, 17, 19-24), and when a specific polymer was not used as copolymer B (Comparative Examples 6, 8, 10, 12, 14, 16, 18), the reduction of the resist pattern top was small, and a resist pattern with high contrast could not be formed.

[0514] [Industrial Applicability]

[0515] According to the present invention, a positive resist composition capable of forming a resist pattern with low reduction of the resist pattern top and high contrast can be provided.

[0516] In addition, according to the present invention, a method for forming a resist pattern can be provided that has a small reduction in the resist pattern top and can also form a resist pattern with high contrast.< / eth>

Claims

Claim 1 The composition comprises copolymer A, copolymer B, and a solvent, wherein the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m² 2 The above is as follows, and the copolymer A is of the following formula (I): A monomer unit (I) represented by [wherein L is a divalent linker having a fluorine atom and Ar is an aromatic ring that may have a substituent] and the following formula (II): [In Equation (II), R 1 is an alkyl group, and R 2 is a hydrogen atom, an alkyl group, a halogen atom, an alkyl halide group, a hydroxyl group, a carboxyl group, or a carboxyl halide group, and R 3 A positive-type resist composition having a monomer unit (II) represented as [where is a hydrogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, p and q are integers from 0 to 5, and p + q = 5.] Claim 2 The composition comprises copolymer A, copolymer B, and a solvent, wherein the difference between the surface free energy of copolymer A and the surface free energy of copolymer B is 4 mJ / m² 2 That is all, and the copolymer B is of the following formula (III): [In Equation (III), R 1 A monomer unit (III) represented by [is an organic group having 5 or more and 7 or less fluorine atoms] and the following formula (IV): [In Equation (IV), R 1 is an alkyl group, and R 2 is a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and R 3 A positive-type resist composition having a monomer unit (IV) represented as [silver, hydrogen atom, unsubstituted alkyl group or alkyl group substituted with a fluorine atom, p and q are integers from 0 to 5, and p + q = 5.] Claim 3 In paragraph 2, the copolymer A is of the following formula (I): A monomer unit (I) represented by [wherein L is a divalent linker having a fluorine atom and Ar is an aromatic ring that may have a substituent] and the following formula (II): [In Equation (II), R 1 is an alkyl group, and R 2 is a hydrogen atom, an alkyl group, a halogen atom, an alkyl halide group, a hydroxyl group, a carboxyl group, or a carboxyl halide group, and R 3 A positive-type resist composition having a monomer unit (II) represented as [where is a hydrogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, p and q are integers from 0 to 5, and p + q = 5.] Claim 4 A positive-type resist composition according to any one of claims 1 to 3, wherein at least one of copolymer A and copolymer B is a main chain-cleaving copolymer containing a halogen atom. Claim 5 A positive-type resist composition according to claim 4, wherein at least one of copolymer A and copolymer B comprises a fluorine substituent, at least one of the halogen atoms is a fluorine atom, and the fluorine atom is included in the fluorine substituent. Claim 6 A positive-type resist composition according to any one of claims 1 to 3, substantially not comprising a component having a weight average molecular weight (Mw) of less than 1000. Claim 7 In claim 1, at least one of copolymer A and copolymer B is of the following formula (V): [In formula (V), X is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or an alkyl halide group, and R 1 A positive-type resist composition having a monomer unit (V) represented as [an organic group having 3 or more and 10 or fewer fluorine atoms]. Claim 8 A method for forming a resist pattern, comprising: a process of forming a resist film using a positive-type resist composition described in any one of claims 1 to 3; a process of exposing the resist film to light; and a process of developing the exposed resist film. Claim 9 A method for forming a resist pattern according to claim 8, wherein the above phenomenon is performed using alcohol.

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