Fluorine-containing polymer

Abstract

The present invention provides a fluorine-containing polymer for a solution for film formation, which is capable of forming a film that is less likely to generate a residue when immersed in a developer. The fluorine-containing polymer of the present invention is characterized by containing a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), the content of the repeating unit represented by the formula (2) being 1500 ppm or less in terms of mass per million based on the repeating unit represented by the formula (1). In the formula (1) and the formula (2), R 1 , R 2 each independently is a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, or a t-butyl group, R 3 , R 4 each independently is a hydrogen atom, a methyl group, or an ethyl group, R 5 is a hydrogen atom or a trifluoromethyl group, and R 6 is a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.

Description

Technical Field

[0001] This invention relates to fluoropolymers. Background Technology

[0002] Fluoropolymers (fluorinated compounds) continue to be used and developed in a wide range of applications, primarily in the field of advanced materials, due to the hydrophobic, oleophobic, low water absorption, heat resistance, weather resistance, corrosion resistance, transparency, photosensitivity, low refractive index, and low dielectric properties of fluorine. In particular, active research and development has been conducted in areas such as coating applications, including antireflective films with low refractive index and visible light transmittance, optical devices with high wavelength (optical communication band) transmittance, and photoresist materials with ultraviolet (especially vacuum ultraviolet) transmittance. As a polymer design applicable to these applications, the aim is to achieve transmittance at all wavelengths by incorporating as much fluorine as possible, while also ensuring good adhesion to the substrate and a high glass transition point (hardness).

[0003] As a monomer constituting such a fluoropolymer, Patent Document 1 describes a polymerizable monomer represented by the following formula (6).

[0004] [Chemical Formula 1]

[0005]

[0006] (In equation (6), R) 1p R represents a group selected from hydrogen atoms, halogen atoms, hydrocarbon groups, and fluorinated alkyl groups (which may be straight-chain or branched and may contain cyclic structures). 2p It is a divalent to trivalent organic group, which is selected from aliphatic hydrocarbon groups (which are straight-chain or branched and can contain cyclic structures), aromatic cyclic groups, or complex substituents thereof, wherein some or all of its hydrogen atoms can be replaced by fluorine atoms or hydroxyl groups. R 3p It can be a hydrogen atom, a hydrocarbon group, a fluorinated alkyl group (which can be straight-chain or branched and may contain a cyclic structure), or an aromatic cyclic group. Within the hydrocarbon group or the fluorinated alkyl group, a divalent linking group selected from ether groups (-O-) and carbonyl groups (-(C=O)-) may be included. m represents an integer from 1 to 2. When m is 2, the two R groups... 3p They can be the same group or different groups.

[0007] The polymerizable monomer shown in formula (6) is (CF3)2(OR) derived from hexafluoroacetone. 3p A monomeric compound with a high fluorine content at the C- site and which successfully achieves a good balance of polar groups within the same molecule.

[0008] It is known that the polymerizable monomer also has excellent polymerizability. The fluoropolymer obtained by polymerizing the polymerizable monomer has both the permeability brought by fluorine atoms and the tightness and processability brought by polar groups. It has excellent physical properties as an anti-reflective film material, optical device material, and photoresist material.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent No. 4083399. Summary of the Invention

[0012] The problem the invention aims to solve

[0013] When a fluoropolymer manufactured using the polymerizable monomer shown in formula (6) is used as a resist material, the fluoropolymer is dissolved in a solvent to form a film-forming solution containing the fluoropolymer.

[0014] A film is formed by applying the film-forming solution to a substrate, a thin film such as a resist film, and baking it. Sometimes, residue is generated on the substrate when the film is immersed in a developer.

[0015] The objective of this invention is to provide a fluoropolymer for use in film-forming solutions, which is capable of forming a film that does not easily produce residue when immersed in a developer.

[0016] Solution for solving the problem

[0017] The inventors conducted in-depth research to address the aforementioned problems. They discovered that the byproducts generated during the production of polymerizable monomers are the cause of these problems. By reducing the content of these byproducts when polymerizing the monomers to manufacture fluoropolymers, the problems can be solved, thus completing this invention.

[0018] That is, the present invention is as follows.

[0019] The fluoropolymer of the present invention is characterized by comprising repeating units shown in formula (1) and repeating units shown in formula (2), wherein the content of repeating units shown in formula (2) is 1500 ppm or less, expressed as a mass fraction based on the repeating units shown in formula (1).

[0020] [Chemical Formula 2]

[0021]

[0022] (In equations (1) and (2), R) 1 R 2Each of the following is independently a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, R 3 R 4 Each is independently a hydrogen atom, methyl or ethyl, R 5 R is a hydrogen atom or a trifluoromethyl group. 6 (It can be a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.)

[0023] In the fluoropolymers of the present invention, R is preferred. 5 It is trifluoromethyl.

[0024] In the fluoropolymers of the present invention, R is preferred. 3 and R 4 It is a hydrogen atom.

[0025] In the fluoropolymers of the present invention, R is preferred. 1 Methyl or isopropyl, R 2 It is a hydrogen atom.

[0026] The fluoropolymer of the present invention preferably contains repeating units other than those shown in formula (1) and formula (2) above.

[0027] The fluoropolymer of the present invention is preferably used in film-forming solutions.

[0028] Invention Effects

[0029] The present invention provides a fluoropolymer for use in film-forming solutions, which can form a film that does not easily produce residue when immersed in a developer. Detailed Implementation

[0030] The present invention will now be described in detail, but the description of the constituent elements described below is only one example of an embodiment of the present invention, and the present invention is not limited to these specific contents. Various modifications can be made within the scope of the spirit of the present invention.

[0031] In the "Detailed Implementation" section of this specification, the items indicated by "[" and "]", "<" and ">" are merely symbols and have no meaning of their own.

[0032] The fluoropolymer of the present invention is characterized by comprising repeating units shown in formula (1) and repeating units shown in formula (2), wherein the content of repeating units shown in formula (2) is 1500 ppm or less, expressed as a mass fraction based on the repeating units shown in formula (1).

[0033] [Chemical Formula 3]

[0034]

[0035] (In equations (1) and (2), R) 1 R 2 Each of the following is independently a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, R 3 R 4 Each is independently a hydrogen atom, methyl or ethyl, R 5 R is a hydrogen atom or a trifluoromethyl group. 6 (It can be a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.)

[0036] The fluoropolymer of the present invention can be used as a resist film, a protective film for the resist film, and / or a top film for the resist pattern (hereinafter also simply referred to as "top film"). In this case, the fluoropolymer is dissolved in a solvent to prepare a film-forming solution containing the fluoropolymer.

[0037] The repeating unit shown in formula (2) is a repeating unit derived from the fluorinated monomer synthesized as an unavoidable byproduct during the manufacture of the fluorinated polymer of the present invention.

[0038] In a fluoropolymer containing repeating units shown in formula (1) and repeating units shown in formula (2), when the proportion of repeating units shown in formula (2) is large, the film-forming solution containing the fluoropolymer is applied to a substrate, applied to a thin film such as a resist film, and a film is formed by baking. Then, when the film is immersed in a developing solution, residue is easily left behind.

[0039] However, in the fluoropolymer of the present invention, the proportion of repeating units shown in formula (2) is sufficiently small. Therefore, when forming a film using a film-forming solution containing the fluoropolymer of the present invention, if the film is immersed in a developing solution, the film dissolves rapidly and does not easily produce residue.

[0040] Furthermore, in the fluoropolymer of the present invention, the content of the repeating unit shown in formula (2), expressed as a mass fraction based on the repeating unit shown in formula (1), is 1500 ppm or less, preferably 450 ppm or less, and more preferably 200 ppm or less. In addition, the content of the repeating unit shown in formula (2) is preferably 10 ppm or more.

[0041] When describing the fluoropolymer of the present invention, its manufacturing method is of particular importance. Therefore, the manufacturing method of the fluoropolymer of the present invention will be described in detail.

[0042] The method for manufacturing the fluoropolymer of the present invention includes a fluorinated monomer synthesis step, a fluorinated monomer purification step, and a polymerization step. Each step is described below.

[0043] <Fluorine-containing monomer synthesis process>

[0044] In the process of synthesizing fluorine-containing monomers, the diol represented by the following formula (3) is reacted with at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids (hereinafter also referred to as "unsaturated carboxylic acids, etc.").

[0045] Thus, it is possible to obtain a composition comprising a fluorinated monomer as shown in formula (4) as the main reactant and a fluorinated monomer as shown in formula (5) as a side reactant.

[0046] [Chemical Formula 4]

[0047]

[0048] (In equations (3), (4) and (5), R) 1 R 2 Each of the following is independently a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, R 3 R 4 Each is independently a hydrogen atom, methyl or ethyl, R 5 R is a hydrogen atom or a trifluoromethyl group. 6 (It can be a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.)

[0049] In the reaction of the fluorinated monomer synthesis process, the diol shown in formula (3) has two alcohol sites within the same molecule: a fluorinated alcohol site containing a fluorine atom and an alkyl alcohol site without a fluorine atom. The fluorinated alcohol site has an electron-withdrawing trifluoromethyl group and a large volume.

[0050] It is speculated that the nucleophilicity of the non-covalent electron pairs of the alcohol site is suppressed due to the electron-withdrawing nature and steric effect of the fluorinated alcohol site, making it difficult for the addition reaction of unsaturated carboxylic acids to occur. The fluorinated monomer shown in formula (4) can be synthesized as the main reactant.

[0051] Furthermore, the fluorinated monomer shown in formula (4) contains a residual fluorinated alcohol site. A small amount of addition reaction of unsaturated carboxylic acids, etc., will occur at this fluorinated alcohol site. Therefore, when synthesizing the fluorinated monomer shown in formula (4), the fluorinated monomer shown in formula (5) is synthesized as an unavoidable byproduct.

[0052] As a result, the composition obtained in the fluorinated monomer synthesis process contains a fluorinated monomer of formula (4) as the main reactant and a fluorinated monomer of formula (5) as a side reactant.

[0053] In addition, during the synthesis of fluorine-containing monomers, sometimes unsaturated carboxylic acids or the like are added to the addition site of the unsaturated carboxylic acid or the like of the fluorine-containing monomer shown in formula (4) to synthesize the fluorine-containing monomer shown in formula (7) below.

[0054] The composition obtained in the fluorine monomer synthesis process may contain the fluorine monomer shown in formula (7).

[0055] [Chemical Formula 5]

[0056]

[0057] (In equation (7), R) 1 R 2 Each of the following is independently a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, R 3 R 4 Each is independently a hydrogen atom, methyl or ethyl, R 5 R is a hydrogen atom or a trifluoromethyl group. 6 (It can be a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.)

[0058] In addition, the fluoropolymer of the present invention may contain repeating units from the monomer shown in formula (7).

[0059] Furthermore, as mentioned above, in the diols shown in formula (3), addition reactions of unsaturated carboxylic acids, etc., are not easily observed at the fluorinated alcohol sites containing fluorine atoms. Therefore, compounds that undergo addition reactions of unsaturated carboxylic acids, etc., only at the fluorinated alcohol sites containing fluorine atoms are almost never produced. Moreover, even if such compounds are generated, addition reactions of unsaturated carboxylic acids, etc., will rapidly occur at the highly reactive alkyl alcohol sites that do not contain fluorine atoms, thus synthesizing the fluorinated monomer shown in formula (5).

[0060] Therefore, in the compositions obtained in the fluorine-containing monomer synthesis process, it is almost impossible to detect compounds as shown in formula (3), in which the addition reaction of unsaturated carboxylic acids, etc., occurs only at the fluorine-containing alcohol site containing fluorine atoms.

[0061] In the diol shown in equation (3), from the point of view of easy availability, R 1 Preferably methyl or isopropyl, R 2 ~R 4 Preferably, hydrogen atoms, R 5 Trifluoromethyl is preferred.

[0062] When using the diol shown in formula (3), in the fluoropolymer of the present invention, the R of the repeating unit shown in formula (1) and the repeating unit shown in formula (2) 1 It is methyl or isopropyl, R 2 ~R 4 For hydrogen atoms, R 5 It is trifluoromethyl.

[0063] Examples of agents used in the synthesis of fluorinated monomers include at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids, such as methacrylic agents, acrylate agents, and other esterifying agents.

[0064] Examples of methacrylic agents used in the synthesis of fluorinated monomers include: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, and other methacrylates; acyl halides such as methacryloyl chloride, methacryloyl fluoride, and methacryloyl bromide; methacrylic anhydride; and methacrylic acid.

[0065] Acrylates used in the synthesis of fluorinated monomers include: methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, and other acrylates; acyl halides such as acyl chloride, acyl fluoride, and acyl bromide; acrylic anhydride; and acrylic acid.

[0066] Examples of esterifying agents used in the synthesis of fluorinated monomers include the methacrylating agents mentioned above and carboxylic acid esters, acyl halides such as carboxyl chlorides, carboxylic anhydrides, and carboxylic acids that are not included in the acrylates mentioned above.

[0067] Among these, methacrylic agents are preferred, and methacrylic anhydride and / or methacryloyl chloride are more preferred.

[0068] In the synthesis of fluorine-containing monomers, when the diol represented by formula (3) reacts with at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids, an acid or base may be added as needed.

[0069] In the synthesis of fluorine-containing monomers, the reaction conditions for reacting the diol represented by formula (3) with at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids are preferably 30 to 130°C for 0.5 to 8 hours.

[0070] In the synthesis process of fluorinated monomers, the amount of fluorinated monomers represented by formula (5) generated as byproducts varies depending on the type of unsaturated carboxylic acid, reaction temperature, and reaction time.

[0071] When the amount of unsaturated carboxylic acids used is too small, the amount of fluorinated monomers shown in formula (5) can be reduced, but a large amount of unreacted diols shown in formula (3) remain. Therefore, it is necessary to separate the fluorinated monomers shown in formula (4) from the diols shown in formula (3).

[0072] Furthermore, when excessive amounts of unsaturated carboxylic acids are used, the amount of fluorinated monomers represented by formula (5) increases. Additionally, homopolymers of unsaturated carboxylic acids are sometimes formed.

[0073] For this reason, the preferred molar ratio of the diol represented by formula (3) to at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids is [molar amount of the diol represented by formula (3)] : [molar amount of at least one selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, acyl halides of unsaturated carboxylic acids, and anhydrides of unsaturated carboxylic acids] = 1 : 0.7 to 1 : 1.3.

[0074] Preferred compounds of the fluorinated monomer of formula (4) obtained in the fluorinated monomer synthesis process include 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate as the fluorinated monomer of formula (4-1) below and 1,1,1-trifluoro-2-hydroxy-2-trifluoromethylheptane-4-yl methacrylate as the fluorinated monomer of formula (4-2) below.

[0075] [Chemical Formula 6]

[0076]

[0077] <Fluorine-containing monomer purification process>

[0078] In the purification process of the fluorinated monomer, the fluorinated monomer shown in formula (5) is removed from the composition obtained by the synthesis process of the fluorinated monomer, and the content of the fluorinated monomer shown in formula (5) is expressed as a mass fraction of parts per million based on the fluorinated monomer shown in formula (4), so that the content of the fluorinated monomer shown in formula (5) is less than 1500 ppm.

[0079] Furthermore, the content of the fluorinated monomer shown in Formula (5) is preferably 450 ppm or less, more preferably 200 ppm or less. Additionally, the content of the fluorinated monomer shown in Formula (5) is preferably 10 ppm or more.

[0080] By performing this process, the content of the repeating unit shown in formula (2) in the fluorinated monomer of the present invention, expressed as a mass fraction based on the repeating unit shown in formula (1), can be made to be less than 1500 ppm.

[0081] There are no particular limitations on the method for removing the fluorinated monomer represented by formula (5) from the composition, and known methods such as column chromatography, precision distillation, or crystallization can be used. These methods can be combined to obtain the fluorinated monomer represented by formula (4) with high purity.

[0082] The methods are described in detail below.

[0083] [Column Chromatography]

[0084] A filler is filled into a conventional cylindrical substrate for column use, and an organic solvent is used as the mobile phase to flow the composition, thereby removing the fluorinated monomer represented by formula (5) from the composition.

[0085] The filler is not particularly limited, but silica gel and alumina gel are preferred, and alumina gel is more preferred. One type of filler or two or more types of fillers may be used.

[0086] There are no particular limitations on the mobile phase; common organic solvents such as hexane, heptane, toluene, and ethyl acetate can be used. Furthermore, one or more mobile phases can be used.

[0087] The temperature for column chromatography is preferably in the range of 0°C to 40°C, and more preferably in the range of 20°C to 30°C.

[0088] Increasing the amount (height) of filler requires more time, but it improves separation. When using cylindrical substrate for columns, specifically model ILC-B22-300 manufactured by Kiriyama Corporation, a filler height of 5cm to 15cm is preferred.

[0089] [Precision Distillation]

[0090] When using precision distillation to remove the fluorinated monomers of formula (5) from the composition, the theoretical number of the distillation column required is more than 5 plates and less than 40 plates.

[0091] When the theoretical number of trays is less than 5, it is difficult to completely remove the fluorine-containing monomers shown in equation (5). The higher the number of trays in the distillation column, the higher the ability to separate and remove the fluorine-containing monomers shown in equation (5), but if it exceeds 40 trays, the separation and removal capacity approaches the upper limit, and it is not easy to improve cost-effectiveness.

[0092] Furthermore, during precision distillation, the fluorinated monomers shown in formula (4) may sometimes undergo polymerization. To prevent such polymerization, a polymerization inhibitor can be added to the composition.

[0093] In addition, oxygen can be introduced into the distillation column.

[0094] As polymerization inhibitors, there are no particular limitations, but examples include: o-cresol, m-cresol, p-cresol, 6-tert-butyl-2,4-dicresol, 2,6-di-tert-butyl-p-cresol, hydroquinone, catechol, 4-tert-butylpyrocatechol, 2,5-bistetramethylbutylhydroquinone, 2,5-di-tert-butylhydroquinone, p-methoxyphenol, 1,2,4-trihydroxybenzene, 1,2-benzoquinone, 1,3-benzoquinone, 1,4-benzoquinone, quinone cryptochrome, phenothiazine, 2-methoxyphenothiazine, tetraethylthiuram disulfide, 1,1-diphenyl-2-picrylhydrazine, or 1,1-diphenyl-2-picrylhydrazine.

[0095] Commercially available polymerization inhibitors include: N,N′-di-2-naphthyl-p-phenylenediamine (trade name: NONFLEX F), N,N-diphenyl-p-phenylenediamine (trade name: NONFLEX H), 4,4′-bis(a,a-dimethylbenzyl)diphenylamine (trade name: NONFLEX DCD), 2,2′-methylene-bis(4-methyl-6-tert-butylphenol) (trade name: NONFLEX MBP), N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine (trade name: OZONE 35), or ammonium N-nitrosophenylhydroxylamine (trade name: Q-1300) or aluminum salt of N-nitrosophenylhydroxylamine (trade name: Q-1301) manufactured by Wako Pure Chemical Industries, Ltd.

[0096] The amount of polymerization inhibitor used in precision distillation is not particularly limited. Based on the amount of fluorinated monomer shown in formula (4) before precision distillation, it is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.01 parts by mass or more and 1 part by mass or less.

[0097] Compared to 100 parts by mass of the fluorinated monomer shown in formula (4), when the polymerization inhibitor is less than 0.01 parts by mass, it is difficult to prevent the polymerization of the fluorinated monomer shown in formula (4).

[0098] Compared to 100 parts by mass of the fluorinated monomer shown in formula (4), when the polymerization inhibitor is greater than 5 parts by mass, the effect of preventing the polymerization of the fluorinated monomer shown in formula (4) is close to the upper limit, and it is not easy to improve cost-effectiveness.

[0099] In addition, the content of the fluorinated monomer represented by formula (4) in the composition can be determined by gas chromatography.

[0100] [Crystallization]

[0101] The fluorinated monomers represented by formula (5) can be removed from the composition by crystallization.

[0102] Crystallization is an operation in which the composition is dissolved in a good solvent, and the fluorine-containing monomer shown in formula (4) is precipitated by adding a poor solvent or lowering the temperature, thereby allowing crystal growth.

[0103] Regarding the type of solvent used for crystallization, any fluorinated monomer shown in formula (4) that is readily soluble or insoluble is acceptable, with no particular restrictions. Examples include alcohols, nitriles, ketones, amides, sulfoxides, ethers, hydrofluorocarbons, hydrofluoroethers, hydrocarbons, aromatic hydrocarbons, or water.

[0104] Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, ethylene glycol, and propylene glycol.

[0105] Examples of nitrile compounds include acetonitrile and benzyl nitrile.

[0106] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, and methyl isobutyl ketone.

[0107] Examples of amides include N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidineone.

[0108] Examples of sulfoxides include dimethyl sulfoxide.

[0109] Examples of ethers include diethyl ether, methyl tert-butyl ether, diisopropyl ether, dibutyl ether, and tetrahydrofuran.

[0110] Examples of hydrofluorocarbons include trifluoromethane, difluoromethane, 1,1,1,2-tetrafluoroethane, 1,1,1-tetrafluoroethane, 1,1-difluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,3,3,3-hexafluoropropane, 1,1,1,3,3-heptafluoropropane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, and 1,1,2,2,3,3,4-heptafluorocyclopentane.

[0111] Examples of hydrofluoroethers include methyl 1,1,2,2,2-pentafluoroethyl ether, methyl trifluoromethyl ether, methyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane, (2,2,3,3-tetrafluoropropyl)(1,1,2,3,3,3-hexafluoropropyl) ether, (methyl)(nonafluorobutyl) ether, (methyl)(nonafluoroisobutyl) ether, (ethyl)(nonafluorobutyl) ether, (ethyl)(nonafluoroisobutyl) ether, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane, 2-trifluoromethyl-3-ethoxydodecylfluorohexane, and 1,1,1,2,3-hexafluoro-4-(1,1,2,3,3,3-hexafluoropropoxy)pentane.

[0112] Examples of hydrocarbons include butane, pentane, hexane, heptane, octane, nonane, and decane.

[0113] Examples of aromatic hydrocarbons include benzene, toluene, xylene, mesitylene, and perfluorobenzene.

[0114] It is preferred to use a compound selected from at least one of these solvents as a good solvent or a bad solvent.

[0115] The amount of solvent used for crystallization is, based on the amount of fluorinated monomer shown in formula (4) before crystallization, 50 parts by mass or more and 2000 parts by mass or less, more preferably 100 parts by mass or more and 1000 parts by mass or less, relative to 100 parts by mass of the fluorinated monomer shown in formula (4).

[0116] When the amount of solvent is less than 50 parts by mass relative to 100 parts by mass of the fluorinated monomer shown in formula (4), it is not easy to stir and mix the slurry of the fluorinated monomer shown in formula (4) that precipitates through crystallization.

[0117] Compared to 100 parts by mass of the fluorinated monomer shown in formula (4), even if more than 2000 parts by mass of solvent are added to dissolve it, the efficiency of removing impurities is close to the upper limit, and it is not easy to improve cost-effectiveness.

[0118] In addition, the content of the fluorinated monomer represented by formula (4) in the composition can be determined by gas chromatography.

[0119] <Polymerization Process>

[0120] In the polymerization process, the fluorinated monomers shown in formula (4) are polymerized using the composition after the fluorinated monomer purification process to form a fluorinated polymer containing repeating units shown in formula (1).

[0121] Furthermore, the composition after the fluorinated monomer purification process contains fluorinated monomers of formula (5) that have not been completely removed, and therefore the fluorinated monomers of formula (5) will also polymerize. Therefore, the fluorinated polymer of the present invention contains repeating units of formula (2).

[0122] In addition, during the polymerization process, there are also cases where unsaturated carboxylic acids, which have undergone addition reactions with the fluorinated alcohol sites containing fluorine atoms in the fluorinated monomers shown in formula (5), undergo polymerization.

[0123] Therefore, the fluoropolymer obtained in this invention may contain repeating units as shown in formula (8).

[0124] [Chemical Formula 7]

[0125]

[0126] (In equation (8), R) 1 R 2 Each of the following is independently a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, R 3 R 4 Each is independently a hydrogen atom, methyl or ethyl, R 5 R is a hydrogen atom or a trifluoromethyl group. 6 (It can be a hydrogen atom, a chlorine atom, a methyl group, or a trifluoromethyl group.)

[0127] Furthermore, in the polymerization process, there are also cases where unsaturated carboxylic acids that have undergone addition reactions with alkyl alcohol sites that do not have fluorine atoms in the fluorinated monomer shown in formula (5), and unsaturated carboxylic acids that have undergone addition reactions with fluorinated alcohol sites that contain fluorine atoms, are polymerized together.

[0128] Therefore, the fluoropolymers of the present invention may contain such repeating units.

[0129] In the polymerization process, other monomers besides the fluorinated monomers shown in formula (4) and formula (5) can be added to the composition after the fluorinated monomer purification process, and the composition can be used for polymerization reaction.

[0130] In this case, the resulting fluoropolymer of the present invention contains repeating units from other monomers. That is, the fluoropolymer of the present invention may contain repeating units other than those shown in formula (1) and formula (2).

[0131] Other monomers besides the fluorinated monomers shown in formula (4) and formula (5) include, for example, the following monomers.

[0132] That is, monomers having a hexafluoroisopropanol group (-C(CF3)2OH), acrylates, methacrylates, fluorinated acrylates, fluorinated methacrylates, styrene, fluorinated styrene, vinyl ethers, fluorinated vinyl ethers, allyl ethers, fluorinated allyl ethers, unsaturated amides, alkenes, fluorinated alkenes, norbornene compounds, fluorinated norbornene compounds, vinyl silanes, vinyl sulfonic acid or vinyl sulfonate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, sulfur dioxide, etc.

[0133] In addition, monomers containing acid-degrading groups can also be used as other monomers.

[0134] Fluoropolymers are manufactured by using monomers containing acid-decomposing groups. When the fluoropolymers are used as photoresists, the photoresist film formed on the substrate is exposed to high-energy radiation such as electromagnetic waves or electron beams with wavelengths below 300 nm. As a result, the acid-decomposing groups decompose and produce acid in the photoresist film.

[0135] This acid can improve the solubility of the resist film in the exposed part of the developing process in the alkaline developing solution.

[0136] In addition, monomers with lactone structures can also be used as other monomers.

[0137] By using monomers with lactone structures to manufacture fluorinated copolymers, the adhesion between the resist film containing the fluorinated copolymer and the substrate can be improved when the fluorinated polymer is used as a photoresist. Furthermore, when using this fluorinated copolymer to form the upper layer film on a photoresist pattern, not only is the adhesion to the lower photoresist pattern improved, but the affinity with the developer during development is also enhanced, resulting in a highly refined photoresist pattern.

[0138] These other monomers can be added one or more.

[0139] The following monomers can be cited as monomers having a hexafluoroisopropanol group.

[0140] [Chemical Formula 8]

[0141]

[0142] (R 7 (The hydrogen atom can be a hydrogen atom, methyl group, fluorine atom, or trifluoromethyl group; the hydrogen atom of the hydroxyl group can be replaced by a protecting group.)

[0143] Examples of acrylates include: methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tert-butyl acrylate, 3-oxocyclohexyl acrylate, adamantyl acrylate, methyl adamantyl acrylate, ethyl adamantyl acrylate, hydroxy adamantyl acrylate, cyclohexyl acrylate, tricyclodecyl acrylate, etc.

[0144] Examples of methacrylates include: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tert-butyl methacrylate, 3-oxocyclohexyl methacrylate, adamantyl methacrylate, methyladamantyl methacrylate, ethyladamantyl methacrylate, hydroxyadamantyl methacrylate, cyclohexyl methacrylate, tricyclodecyl methacrylate, etc.

[0145] As fluorinated acrylates and fluorinated methacrylates, they can be acrylates or methacrylates containing a fluorine atom or an alkyl group having a fluorine atom at the α-position of the acrylic acid structure, or they can be acrylates or methacrylates containing a fluorine atom or an alkyl group having a fluorine atom in the ester structure.

[0146] In fluorinated acrylates or fluorinated methacrylates, both the α-position and the ester site of the acrylic acid structure can contain a fluorine atom or an alkyl group with a fluorine atom. Alternatively, a cyano group can be introduced at the α-position of the acrylic acid structure.

[0147] In fluorinated acrylates or fluorinated methacrylates, alkyl groups having fluorine atoms introduced at the α-position of the acrylic acid structure can be specifically exemplified by trifluoromethyl, trifluoroethyl, and nonafluorobutyl.

[0148] In fluorinated acrylates or fluorinated methacrylates, the ester structure can have a fluorinated alkyl group such as a perfluoroalkyl or fluoroalkyl group. Furthermore, a cyclic structure and a fluorine atom can coexist in the ester structure. Moreover, the cyclic structure can also be a fluorinated benzene ring, a fluorinated cyclopentane ring, a fluorinated cyclohexane ring, or a fluorinated cycloheptane ring, etc., having a fluorine atom, trifluoromethyl group, hexafluoroisopropylhydroxyl group, etc. Additionally, the ester structure can also be a tert-butyl ester group having a fluorine atom.

[0149] Examples of such fluorinated acrylates include: 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, heptafluoroisopropyl acrylate, 1,1-dihydroheptafluorobutyl acrylate, 1,1,5-trihydrooctafluoropentyl acrylate, 1,1,2,2-tetrahydrotridecylfluorooctyl acrylate, and acrylic acid. Perfluorocyclohexyl methyl ester, 6-[3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl)propyl]bicyclo[2.2.1]heptyl-2-yl ester, 6-[3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl)propyl]bicyclo[2.2.1]heptyl-2-yl-2-(trifluoromethyl) ester, 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl-2-trifluoromethyl ester, etc.

[0150] Examples of fluorinated methacrylates include: 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, heptafluoroisopropyl methacrylate, 1,1-dihydroheptafluorobutyl methacrylate, 1,1,5-trihydrooctafluoropentyl methacrylate, 1,1,2,2-tetrahydrotridecylfluorooctyl methacrylate, and 1,1... 2,2-Tetrahydroheptadecyl fluorodecyl ester, perfluorocyclohexyl methyl methacrylate, 6-[3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl)propyl]bicyclo[2.2.1]heptyl-2-yl ester of methacrylate, 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl ester of methacrylate, 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl ester of methacrylate, etc.

[0151] Examples of styrene-based and fluorinated styrene-based products include styrene, hydroxystyrene, and fluorinated styrene.

[0152] Fluorinated styrene can be pentafluorostyrene, trifluoromethylstyrene, bis(trifluoromethylstyrene), etc., which are styrene in which a fluorine atom or a trifluoromethyl group replaces a hydrogen atom in the aromatic ring. Alternatively, it can be styrene in which a hexafluoroisopropanol group is substituted for a hydrogen atom in the aromatic ring, or a hexafluoroisopropanol group or a hydroxyl group protected by a protecting group. Furthermore, it can also be the above-mentioned styrene with a halogen, alkyl group, or fluoroalkyl group bonded at the α-position, or styrene containing a perfluorovinyl group, etc.

[0153] Vinyl ethers, fluorinated vinyl ethers, allyl ethers, and fluorinated allyl ethers may have hydroxyl groups such as methyl, ethyl, propyl, butyl, hydroxyethyl, or hydroxybutyl in their structure.

[0154] In addition, these compounds may contain cyclohexyl, norbornel, aromatic rings in their structure, or be cyclic vinyl or allyl ethers with hydrogen or carbonyl bonds in their cyclic structure, in which some or all of the hydrogen atoms in these structures may be replaced by fluorine atoms.

[0155] Examples of unsaturated amides include: acrylamide, methacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, diacetone acrylamide, etc.

[0156] Examples of olefins include ethylene, propylene, isobutylene, cyclopentene, and cyclohexene.

[0157] Examples of fluorinated olefins include: vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, and hexafluoroisobutylene.

[0158] As a monomer having a norbornene site, the monomer may have more than one norbornene site, and the hydrogen atom of the norbornene site may be replaced by a functional group containing a fluorine atom.

[0159] Examples of such monomers include norbornene compounds synthesized via Diels-Alder addition reactions of cyclopentadiene, cyclohexadiene, and unsaturated compounds.

[0160] Examples of unsaturated compounds used in the synthesis of norbornene compounds include: acrylic acid, methacrylic acid, α-fluoroacrylic acid, α-trifluoromethacrylic acid, acrylates, methacrylates, fluorinated acrylates, fluorinated methacrylates, fluorinated olefins, allyl alcohol, fluorinated allyl alcohol, homoallyl alcohol, fluorinated homoallyl alcohol, 2-(benzoyloxy)pentafluoropropane, 2-(methoxyethoxymethyloxy)pentafluoropropene, 2-(tetrahydroxypyranyloxy)pentafluoropropene, 2-(benzoyloxy)trifluoroethylene, 2-(methoxymethyloxy)trifluoroethylene, 3-(5-bicyclo[2.2.1]hepten-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanol, etc.

[0161] In monomers having acid-degradable groups, any group that is removed from the fluoropolymer by hydrolysis by an acid generated by a photoacid generator contained in the resist can be used without particular restriction. Monomers having acid-degradable groups as shown in formula (9) or formula (10) below are preferred as such acid-degradable groups.

[0162] [Chemical Formula 9]

[0163]

[0164] (In equations (9) and (10), R) 8R 9 R 10 R 12 Each is independently a straight-chain, branched, or cyclic alkyl group having 1 to 25 carbon atoms, or having 3 to 25 carbon atoms. Some or all of the hydrogen atoms in the alkyl group may be substituted with fluorine, oxygen, nitrogen, sulfur, or hydroxyl atoms. R 8 R 9 R 10 Any two elements in R can be combined to form a ring. 11 An alkyl group is a straight-chain group with 1 to 25 carbon atoms, or a branched or cyclic group with 3 to 25 carbon atoms. Some or all of the hydrogen atoms in the alkyl group may be replaced by fluorine, oxygen, nitrogen, sulfur, or hydroxyl atoms. (Dashed lines indicate bonding sites.)

[0165] As acid-degrading groups represented by formulas (9) and (10), specific examples of acid-degrading groups can be found as shown below. Additionally, the dashed lines represent binding sites.

[0166] [Chemical Formula 10]

[0167]

[0168] Examples of monomers having a lactone structure include monocyclic lactone structures such as those obtained by removing a hydrogen atom from γ-butyrolactone or mevalonate lactone, and polycyclic lactone structures such as those obtained by removing a hydrogen atom from norbornane lactone.

[0169] As other monomers described above, preferred monomers are 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl methacrylate as shown in formula (11) and 1,1,2,2-tetrahydroheptadecyl acrylate as shown in formula (12).

[0170] [Chemical Formula 11]

[0171]

[0172] When 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl methacrylate is added, the fluoropolymer of the present invention, when used as a component of the resist film or the top film, has the effect of improving its solubility in organic solvents during the preparation of the coating solution and its solubility in the developing solution during development.

[0173] When 1,1,2,2-tetrahydroheptadecyl acrylate is added, and the resulting fluoropolymer of the present invention is used as a component of the upper film, the adhesion of the upper film to the lower resist film is improved, and the hydrophobicity of the upper film surface is increased. Therefore, the exposure time in immersion exposure with water as the exposure medium can be shortened. In addition, the surface tension can be reduced, resulting in smoothing of the upper film surface and uniformity of film thickness.

[0174] When other monomers are added, their amounts are not particularly limited. In the fluoropolymer of the present invention after polymerization, when the total number of repeating units contained in the fluoropolymer is 100 mol%, the proportion of repeating units from other monomers is preferably 1 mol% or more and 80 mol% or less, more preferably 5 mol% or more and 70 mol% or less, and even more preferably 10 mol% or more and 60 mol% or less.

[0175] If the proportion of repeating units from other monomers is less than 1 mol%, it is difficult to obtain the following effects: the expected effect of improved solubility in organic solvents when using the obtained fluoropolymer as a resist, and the effect of improved adhesion between the resist film and the substrate and improved etch resistance of the resist pattern when forming a resist film on the substrate.

[0176] If the proportion of repeating units from other monomers is greater than 80 mol%, then the proportion of repeating units shown in equation (1) will decrease, making it difficult to achieve the effects of improving the transparency of the resist film and improving the solubility of the solvent.

[0177] The polymerization reaction in the polymerization process is not particularly limited and can be a free radical polymerization reaction, an ionic polymerization reaction, a coordination anionic polymerization reaction, a living anionic polymerization reaction, or a cationic polymerization reaction.

[0178] Of these, free radical polymerization is preferred.

[0179] When the polymerization reaction is a free radical polymerization reaction, any polymerization initiator can be used to initiate the polymerization reaction without any particular limitation. Azo compounds, peroxide compounds, and redox compounds can all be used.

[0180] Azobisisobutyronitrile (DIS) is an example of an azo compound.

[0181] Examples of peroxide compounds include: tert-butyl peroxypentanoate, di-tert-butyl peroxide, isobutyryl peroxide, lauroyl peroxide, succinic acid peroxide, dicinnamyl peroxide, di-n-propyl peroxide dicarbonate, allyl monobutyl peroxide, benzoyl peroxide, hydrogen peroxide, or ammonium persulfate.

[0182] As redox compounds, they use a combination of oxidizing and reducing agents. Examples of oxidizing agents include hydrogen peroxide, persulfate, and cumene hydroperoxide, while examples of reducing agents include iron(II) ion salts, copper(I) ion salts, ammonia, and triethylamine.

[0183] In addition, polymerization solvents can be used in free radical polymerization reactions.

[0184] As a polymerization solvent, there are no particular limitations as long as the solvent does not hinder the free radical polymerization reaction; it can be an organic solvent or water.

[0185] Examples of organic solvents include hydrocarbon solvents, ester solvents, ketone solvents, alcohol solvents, ether solvents, cyclic ether solvents, fluorocarbon solvents, and aromatic solvents.

[0186] These solvents can be used in single or multiple ways.

[0187] Examples of ester-based solvents include acetic acid and n-butyl acetate.

[0188] Examples of ketone solvents include acetone and methyl isobutyl ketone.

[0189] Examples of hydrocarbon solvents include toluene and cyclohexane.

[0190] Examples of alcohol solvents include methanol, isopropanol, and ethylene glycol monomethyl ether.

[0191] In addition, molecular weight regulators such as thiols can be used in free radical polymerization reactions.

[0192] The reaction temperature in the free radical polymerization reaction is appropriately varied depending on the type of free radical polymerization initiator or the type of free radical polymerization initiator. It is preferably above 20°C and below 200°C, and more preferably above 30°C and below 140°C.

[0193] After the polymerization process, known methods can be used to remove the organic solvent or water, which serves as the medium, from the synthesized solution or dispersion containing the fluoropolymer.

[0194] Specifically, methods such as reprecipitation, filtration, and heated distillation under reduced pressure can be cited.

[0195] Through the above processes, the fluoropolymer of the present invention, comprising the repeating unit shown in formula (1) and the repeating unit shown in formula (2), can be manufactured.

[0196] The weight-average molecular weight of the fluoropolymer of the present invention is preferably 5,000 to 20,000, more preferably 7,000 to 12,000.

[0197] Furthermore, the weight-average molecular weight of the fluoropolymers in this specification refers to the value determined by gel permeation chromatography (GPC) under the following conditions.

[0198] [GPC Conditions]

[0199] Device: Made by Tosoh Corporation, HLC-8320GPC

[0200] Chromatographic columns for polymerizable monomer analysis: Tosoh Corporation, TSKgel series (G2500HXL, G2000HXL, G1000HXL, G1000HXL connected in series).

[0201] Chromatographic columns for polymer analysis: Tosoh Corporation, TSKgel series (G2500HXL, G2000HXL, G1000HXL, G1000HXL connected in series).

[0202] Temperature program: 40℃ (hold)

[0203] Flow rate: 1 mL / min

[0204] Detector: Differential Refraction Detector (RI)

[0205] Eluent: Tetrahydrofuran (THF)

[0206] Reference material: polystyrene standard solution

[0207] Next, the method of using the fluoropolymer of the present invention will be described.

[0208] The fluoropolymer of the present invention can be used as a component of resist film.

[0209] Furthermore, the fluoropolymers of the present invention can be used as components of the upper film protecting the resist film and / or the resist pattern.

[0210] In particular, when the fluoropolymer of the present invention contains hexafluoroisopropanol groups in its structure, the use of the fluoropolymer of the present invention enables the formation of an upper film by immersion exposure. In this case, the resist film and / or resist pattern forming the upper film can be either negative or positive.

[0211] When the fluoropolymer of the present invention comprises an aliphatic chain structure and a hexafluoroisopropanol group, it has the characteristic of high light transmittance at wavelengths below 300 nm. In this case, when the fluoropolymer of the present invention is used to form a resist film, electromagnetic waves with wavelengths below 300 nm can be used in its exposure.

[0212] When the fluoropolymer of the present invention is used to form a resist film or an upper film, the weight-average molecular weight of the fluoropolymer of the present invention will affect its solubility in the solvent, the physical properties of the resist film and the upper film after film formation, such as the glass transition temperature Tg.

[0213] When the fluoropolymer of the present invention is used to form a resist film, if the weight-average molecular weight is high, the dissolution rate in the developer tends to be slow. Conversely, if the weight-average molecular weight is low, the dissolution rate in the developer tends to be faster.

[0214] When the fluoropolymer of the present invention is used to form a resist film or an upper film, the fluoropolymer of the present invention is dissolved in a solvent or a mixture of water and solvent and diluted to prepare a film-forming solution.

[0215] When using the fluoropolymer of the present invention to form the upper film, the solvent is preferably one that does not easily erode the resist film and / or resist pattern formed on the upper film, and in which the additives contained herein are not easily dissolved.

[0216] The solvent used to dissolve the fluorinated copolymer of the present invention preferably has a boiling point of 70°C to 170°C.

[0217] If the solvent has a boiling point below 70°C, it will evaporate too quickly and will not easily form a uniform film.

[0218] If the solvent has a boiling point above 170°C, the coating will take longer to dry, which can easily reduce production capacity.

[0219] Furthermore, examples of solvents include hydrocarbon solvents, alcohol solvents, ether solvents, ester solvents, and fluorine solvents. Among these, preferred solvents include alkanes with 5 to 20 carbon atoms, alicyclic hydrocarbon solvents, alcohol solvents with 1 to 20 carbon atoms, and fluorine solvents in which some of the hydrogen atoms in alkanes with 5 to 20 carbon atoms, alicyclic hydrocarbons, and alcohols with 1 to 20 carbon atoms are replaced by fluorine atoms. These can be used individually or in combination with two or more solvents.

[0220] When two or more solvents are used together, the composition of the hydrocarbon solvent and the alcohol solvent is expressed as a mass ratio, preferably a solvent in which the ratio of hydrocarbon solvent to alcohol solvent is 50 to 99.9 to 0.1 to 50.

[0221] Examples of hydrocarbon solvents include pentane, hexane, heptane, octane, nonane, and decane. Examples of alcohol solvents include n-butanol, isobutanol, tert-butanol, methylethylmethanol, pentanol, amyl alcohol, hexanol, heptanol, and 4-methyl-2-pentanol.

[0222] Furthermore, from the viewpoint of being able to quickly dissolve fluoropolymers, fluorinated solvents are preferred.

[0223] Specifically, examples of fluorinated solvents include: 2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole, 2,3-difluoroanisole, 2,4-difluoroanisole, 2,5-difluoroanisole, and 5,8-difluoro-1,4-benzodiphenyl ether. Alkane, 2,3-difluorobenzyl alcohol, 1,3-difluoro-2-propanol, 2',4'-difluorophenylacetone, 2,4-difluorotoluene, trifluoroacetaldehyde ethyl hemiacetal, trifluoroacetamide, trifluoroethanol, 2,2,2-trifluoroethyl butyrate, ethyl heptafluorobutyrate, ethyl heptafluorobutylacetate, ethyl hexafluoroglutaryl methyl ester, ethyl 3-hydroxy-4,4,4-trifluorobutyrate, ethyl 2-methyl-4,4,4-trifluoroacetoacetate, ethyl pentafluorobenzoate, ethyl pentafluoropropionate, ethyl pentafluoropropionylacetate, ethyl perfluorooctanoate, ethyl 4,4,4-trifluoroacetoacetate, ethyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorocrotonate, ethyl trifluoromethanesulfonate, ethyl 3-(trifluoromethyl)butyrate, ethyl trifluoropyruvate, S - Ethyl trifluoroacetate, fluorocyclohexane, 2,2,3,3,4,4,4-heptafluoro-1-butanol, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, 1,1,1,3,5,5,5-heptafluoropentane-2,4-dione, 3,3,4,4,5,5,5-heptafluoro-2-pentanol, 3,3,4,4,5,5,5-heptafluoro-2-pentanone, 4,4,4-trifluoroacetyl acetate isopropyl ester, methyl perfluorodecanoate, methyl perfluoro(2-methyl-3-oxahexanoate), methyl perfluorononanoate, methyl perfluorooctanoate, methyl 2,3,3,3-tetrafluoropropionate, methyl trifluoroacetyl acetate, 1,1,1,2,2,6,6,6-octafluoro-2,4-hexanedione, 2 2,3,3,4,4,5,5-Octafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-decanol, methyl perfluoro(2,5-dimethyl-3,6-dioxanonol), 2H-perfluoro-5-methyl-3,6-dioxanonane, 1H,1H,2H,3H,3H-perfluorononane-1,2-diol, 1H,1H,9H-perfluoro-1-nonanol, 1H,1H-perfluorooctanol, 1H,1H,2H,2H-perfluorooctanol, 2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoctadecane, perfluorotributylamine, perfluorotrihexylamine, methyl perfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoate, perfluorotripentylamine, perfluoro Tripropylamine, 1H,1H,2H,3H,3H-perfluoroundecane-1,2-diol, trifluorobutanol-1,1,1-trifluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propane acetate, perfluorobutyltetrahydrofuran, perfluoro(butyltetrahydrofuran), perfluoronaphthalene, perfluoro(1,2-dimethylcyclohexane), perfluoro(1,3-dimethylcyclohexane), propylene glycol trifluoromethyl ether acetate, propylene glycol methyl ether trifluoromethyl acetate, trifluoromethyl acetate butyl ester, methyl 3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycol trifluoromethyl ether, trifluoroacetate butyl ester, 1,1,1-trifluoro-5,5-dimethyl-2,4-Hexanedione, 1,1,1,3,3,3-Hexafluoro-2-propanol, 1,1,1,3,3,3-Hexafluoro-2-methyl-2-propanol, 2,2,3,4,4,4-Hexafluoro-1-butanol, 2-Trifluoromethyl-2-propanol, 2,2,3,3-Tetrafluoro-1-propanol, 3,3,3-Trifluoro-1-propanol, 4,4,4-Trifluoro-1-butanol, etc.

[0224] They can be used individually or in combination with two or more.

[0225] When the fluoropolymer of the present invention is used to form a resist film or an upper film, it is preferable to dissolve the fluoropolymer in a solvent such that the concentration of the solid component in the film-forming solution is 3% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 15% by mass or less.

[0226] If it falls within the above range, there will be no thickness unevenness, and a resist film or top film can be formed quickly.

[0227] When the fluoropolymer of the present invention is used to form a resist film, the film-forming solution may contain, in addition to the fluoropolymer and solvent, a photoacid generator, a quencher, or other non-fluoropolymers.

[0228] When the fluoropolymer of the present invention is used to form the upper film, the film-forming solution may contain other non-fluoropolymers in addition to the fluoropolymer and solvent.

[0229] When using the fluoropolymer of the present invention to form a resist film, the resist film can be formed by applying a film-forming solution to a substrate and baking it. Then, the formed resist film is immersed in a developing solution to dissolve it.

[0230] The developer is not particularly limited and can be, for example, an aqueous solution of tetramethylammonium hydroxide with a concentration of 0.1% by mass or more and 10% by mass or less.

[0231] In the fluoropolymer of the present invention, the content of the repeating unit shown in formula (2) is less than 1500 ppm, expressed as a mass fraction based on the repeating unit shown in formula (1).

[0232] Therefore, if the formed resist film is immersed in the developer, it will dissolve quickly and will not easily leave residue.

[0233] In this case, there is no particular limitation on the substrate for applying the film-forming solution, and examples include central processing units (CPUs), static random access memory (SRAMs), and dynamic random access memory (DRAMs) disposed on silicon wafers, compound semiconductor substrates, insulating substrates, etc.

[0234] When applying the film-forming solution, the film-forming solution can be directly applied to the substrate to form a resist film, or other layers can be set on the substrate, and then the film-forming solution can be applied to these layers to form a resist film.

[0235] Other examples of layers include anti-reflective films, SiO2 films, and Si3N4 films.

[0236] Anti-reflective films can be formed using, for example, anti-reflective coating agents (such as ARC-type coatings manufactured by Nissan Chemical Co., Ltd.).

[0237] When using a silicon wafer as a substrate, a SiO2 film can be formed on the surface of the silicon wafer by high-temperature steam treatment at 900°C in an oxidation furnace. Furthermore, a Si3N4 film can be formed by chemical vapor deposition (CVD) of SiH2 and NH3 onto the SiO2 film formed on the surface of the silicon wafer.

[0238] When using the fluoropolymer of the present invention to form a resist film, a film-forming solution can be applied to a substrate to form a resist film. The resist film can then be exposed to light or subjected to immersion exposure.

[0239] Furthermore, when using the fluoropolymer of the present invention to form the upper film, the film-forming solution can be applied to the resist film and / or resist pattern to form the upper film. The upper film can then be exposed to light or subjected to immersion exposure.

[0240] There is no particular limitation on the wavelength of the electromagnetic waves used for exposure, but electromagnetic waves with wavelengths below 300 nm are preferred in order to obtain high-precision patterns.

[0241] As an electromagnetic wave irradiator, KrF excimer lasers (wavelength 248nm) and ArF excimer lasers (wavelength 193nm) can be used. Among these, ArF excimer lasers are preferred.

[0242] In addition, extreme ultraviolet (EUV, wavelength 13.5nm), X-rays, and electron beams (EB) can also be used.

[0243] Furthermore, the fluoropolymer of the present invention can be used as the upper layer of the resist film in the manufacture of semiconductor devices. In this case, the upper layer film can be subjected to liquid immersion exposure.

[0244] Semiconductor devices using the fluoropolymer of the present invention are not particularly limited, and examples include central processing units (CPUs), static random access memory (SRAMs), and dynamic random access memory (DRAMs) disposed on silicon wafers, compound semiconductor substrates, insulating substrates, etc.

[0245] In addition, immersion exposure refers to exposure in which the space between the lens of the exposure device and the substrate is filled with a liquid used for immersion.

[0246] Compared to filling the space between the lens and the substrate of the exposure apparatus with air, filling the space between the lens and the substrate with liquid immersion reduces the angle of incidence of the exposure light incident on the substrate through the lens. Therefore, the numerical aperture of the lens can be increased, thereby improving resolution.

[0247] Furthermore, even in exposures using lenses with existing numerical apertures, it is possible to expand the depth focus, ensuring a stable yield.

[0248] Furthermore, during pattern formation in immersion exposure, poor pattern formation can sometimes occur due to the immersion liquid penetrating the resist film. Additionally, poor pattern formation can sometimes result from various components seeping from the resist film into the immersion liquid. Moreover, if droplets remain on the substrate after immersion exposure, they can sometimes become pattern defects.

[0249] During immersion exposure, an upper film is formed on top of the resist film to prevent poor pattern formation, etc.

[0250] The fluoropolymer of the present invention is useful as a material for an upper film formed on such a resist film.

[0251] In immersion exposure, a resist solution is first applied to a substrate such as a silicon wafer using a spin coater. Then, pre-baking is performed to form a resist film.

[0252] Next, using a spin coater or similar device, a film-forming solution containing the fluoropolymer of the present invention is applied to the surface of the formed resist film to a uniform thickness. Then, by performing a heat treatment, an upper film can be formed on the resist film.

[0253] When a substrate with an upper film is immersed in an exposure medium such as water, electromagnetic waves with wavelengths below 300 nm are irradiated onto the upper film and the photoresist film through a mask or intermediate mask etched with a circuit pattern. The electromagnetic waves then travel through the medium (e.g., water) and the upper film to reach the lower photoresist film. Because of the upper film, the photoresist film does not directly contact the exposure medium. Therefore, the exposure medium does not swell due to immersion in the photoresist film, and furthermore, components of the photoresist film are prevented from dissolving into the exposure medium.

[0254] After baking the exposed substrate, development is performed using a developer. Typically, a tetramethylammonium hydroxide aqueous solution with a concentration of 0.1% by mass or more and 10% by mass can be used as the developer. During development, the upper film dissolves, and only the exposed portion of the lower resist film dissolves.

[0255] In the fluoropolymer of the present invention, the content of the repeating unit shown in formula (2) is less than 1500 ppm, expressed as a mass fraction based on the repeating unit shown in formula (1).

[0256] Therefore, if the formed upper film is immersed in the developer, the upper film dissolves rapidly, leaving little residue. The resulting resist pattern has very clear edges.

[0257] The following are specific embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0258] (Preparation of standard samples of the monomer shown in formula (4))

[0259] <Fluorine-containing monomer synthesis process>

[0260] 100 g (0.44 mol) of 1,1,1-trifluoro-2-(trifluoromethyl)pentane-1,3-diol (the compound shown in formula (3-1) below), 74.6 g (0.48 mol) of methacrylic anhydride, 4.2 g (0.044 mol) of methanesulfonic acid, 400 g of toluene, and 0.5 g of phenothiazine were added to a 1 L three-necked flask equipped with a thermometer, reflux condenser, and stirrer. The bottom of the three-necked flask was then immersed in an oil bath heated to 50 °C, and the mixture was reacted with stirring for 4 hours to obtain the composition.

[0261] The composition was determined by gas chromatography. The results showed that, excluding methacrylic acid as a by-reactant, the reaction solution contained 94.5% by mass of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (the compound shown in formula (4-1)), 1.6% by mass of 1,1,1-trifluoro-2-(trifluoromethyl)pentane-1,3-diol, 2.0% by mass of methacrylic anhydride, and 1.9% by mass of other compounds.

[0262] [Chemical Formula 12]

[0263]

[0264] <Fluorine-containing monomer purification process>

[0265] The obtained composition was added to a separatory funnel, followed by 400 g of sodium bicarbonate solution. After washing twice, the organic layer was collected, dried with 30 g of magnesium sulfate, and then filtered to remove the magnesium sulfate. 0.7 g of phenothiazine as a polymerization inhibitor was added to the filtrate. After distilling off the solvent, the solution was subjected to vacuum distillation (8 Torr = 1.1 kPa), and the fraction collected at 80℃–82℃ yielded 112 g of the fraction. The yield was 87%.

[0266] The fraction was analyzed by gas chromatography-mass spectrometry (GC-MS), and the results are shown below. The purity of the target methacrylate-5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl ester (fluorinated monomer shown in formula (4-1)) was 97.0%, and it contained methacrylate-1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-diyl ester (fluorinated monomer shown in formula (5-1) below) as a by-reaction.

[0267] [Chemical Formula 13]

[0268]

[0269] Repeat the above operation to produce a 3.0 kg fraction containing 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (the fluorinated monomer shown in formula (4-1)).

[0270] The obtained fraction was precisely distilled using an Oldershaw distillation column, yielding 2.76 kg of fraction with a boiling point of 80 °C at a pressure of 0.5 kPa.

[0271] The fraction obtained by GC-MS analysis showed that the purity of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (the fluorinated monomer shown in formula (4-1)) was 99.8%.

[0272] The concentration of 1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-dimethyl methacrylate (the fluorinated monomer shown in formula (5-1)) determined by GC-MS before precision distillation was 2600 ppm, but decreased to 10 ppm after precision distillation. Thus, a composition of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (the fluorinated monomer shown in formula (4-1)) with improved purity through precision distillation was obtained. This composition was used as a standard sample of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (the fluorinated monomer shown in formula (4-1)).

[0273] In addition, standard samples of 1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-dimethyl methacrylate (fluorinated monomers shown in formula (5-1)) were prepared by the following method.

[0274] 100 g of a standard sample of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (a fluorinated monomer shown in formula (4-1)) was added to a 1 L three-necked flask equipped with a thermometer, reflux condenser, and stirrer. Then, 60 g of triethylamine, 4 g of N,N-dimethylaminopyridine, and 1 g of phenothiazine were added. The bottom of the flask was immersed in an ice bath, and 79 g of methacrylic anhydride was added dropwise while stirring. The mixture was then brought to room temperature and stirred for one hour to obtain a reaction solution. The reaction solution was transferred to a separatory funnel, diluted with 300 g of toluene, and 200 mL of dilute hydrochloric acid was added to complete the reaction. The organic layer was then separated. The separated organic layer was washed twice with 200 g of water, and the solvent was removed by rotary evaporation. Next, distillation was performed using a distillation apparatus equipped with a Widmanstätten fractionator. The fraction collected at 86 °C–88 °C under a vacuum of 0.5 kPa yielded 16 g of oil. The oil fraction, as determined by GC-MS, contained 96% by mass of 1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-dimethyl methacrylate (the fluorinated monomer shown in formula (5-1)) and 2.5% by mass of unreacted 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-dimethyl methacrylate (the fluorinated monomer shown in formula (4-1)). This oil fraction was used as a standard sample for 1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-dimethyl methacrylate (the fluorinated monomer shown in formula (5-1)).

[0275] (Preparation of the raw material composition used in the polymerization process)

[0276] Using standard samples of 5,5,5-trifluoro-4-hydroxy-4-trifluoromethylpentane-2-yl methacrylate (fluorinated monomer shown in formula (4-1)) and 1,1,1-trifluoro-2-(trifluoromethyl)pentane-2,4-diyl methacrylate (fluorinated monomer shown in formula (5-1)), raw material compositions A to F were prepared in the proportions shown in Table 1.

[0277] [Table 1]

[0278]

[0279] (Example 1)

[0280] <Polymerization Process>

[0281] At room temperature (approximately 20°C), 100g of raw material composition A was added to a 500mL container, along with 200g of 2-butanone containing 6.26g of dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., product name V-601). After preparing a solution of raw material composition A, it was transferred to a dropping funnel. Next, this dropping funnel was attached to a separate 500mL reactor containing 100g of 2-butanone, and the 2-butanone was heated to 78°C.

[0282] The temperature of 2-butanone in the reactor was maintained at 78±1°C. Under this condition, a solution of raw material composition A was slowly added dropwise into the reactor through a dropping funnel over 2 hours. After the addition was completed, the temperature was maintained at 78±1°C for 6 hours and then cooled. At this time, the temperature was slowly reduced to 30°C over 30 minutes to obtain a fluoropolymer containing repeating units shown in formula (1-1) and formula (2-1) below. The obtained fluoropolymer is the fluoropolymer of Example 1.

[0283] The molecular weight of the fluoropolymer in Example 1 was determined by gel permeation chromatography (GPC), and the weight-average molecular weight was 9575 (N=1).

[0284] [Chemical Formula 14]

[0285]

[0286] The fluoropolymer of Example 1 was manufactured five times (N=2-6) in the same manner, for a total of six manufacturing cycles. The weight-average molecular weight of the fluoropolymer of Example 1 in each manufacturing cycle was determined. The results are shown in Table 2.

[0287] Next, the reaction solution containing the above-mentioned fluoropolymer was slowly added dropwise to n-heptane, which was heated to 25°C, while stirring for 1 hour. The mixture was stirred for another hour to obtain a fluoropolymer slurry. The obtained slurry was filtered under reduced pressure to obtain a filter cake. The filter cake was dried to obtain the fluoropolymer powder of Example 1.

[0288] (Example 2) to (Example 5)

[0289] Using raw material compositions B through E instead of raw material composition A, the fluoropolymers of Examples 2 through 5 were manufactured in the same manner as in Example 1. The weight-average molecular weight of the fluoropolymers of Examples 2 through 5 was then determined. The results are shown in Table 2.

[0290] (Example 6)

[0291] At room temperature (approximately 20°C), 80g of raw material composition A and 20g of 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl methacrylate (the monomer shown in formula (11)) were added to a 500mL container. 200g of 2-butanone containing 6.26g of dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., product name V-601) was added. After preparing a mixed solution with raw material composition A, the solution was transferred to a dropping funnel. Next, this dropping funnel was installed on a separate 500mL reactor containing 100g of 2-butanone, and the 2-butanone was heated to 78°C.

[0292] The temperature of 2-butanone in the reactor was maintained at 78±1°C. Under this condition, and with a nitrogen flow, the above mixed solution was slowly added dropwise to the reactor through a dropping funnel over 2 hours. After the addition was completed, the temperature was maintained at 78±1°C for 6 hours and then cooled. At this time, the temperature was slowly reduced to 30°C over 30 minutes to obtain a fluoropolymer containing repeating units shown in formula (1-1), repeating units shown in formula (2-1), and repeating units shown in formula (11-1). The obtained fluoropolymer is the fluoropolymer of Example 6.

[0293] Next, 2-butanone was removed from the reaction solution, and the molecular weight of the fluoropolymer of Example 6 was determined by GPC, which showed to be 9669 (N=1).

[0294] [Chemical Formula 15]

[0295]

[0296] The reaction solution of the fluoropolymer of Example 6 was prepared five times (N=2-6) in the same manner, for a total of six preparations. The weight-average molecular weight of the fluoropolymer of Example 6 in each preparation was determined. The results are shown in Table 2.

[0297] (Example 7)

[0298] The fluoropolymer of Example 7 was prepared in the same manner as in Example 6, except that raw material composition C was used instead of raw material composition A. The weight-average molecular weight of the fluoropolymer of Example 7 was then determined. The results are shown in Table 2.

[0299] (Example 8)

[0300] At room temperature (approximately 20°C), 95g of raw material composition A and 5g of 1,1,2,2-tetrahydroheptadecyl acrylate (the monomer shown in formula (12)) were added to a 500mL container. 200g of 2-butanone containing 6.26g of dimethyl-2,2'-azobis(2-methylpropionate) was added. After preparing a mixed solution with raw material composition A, the solution was transferred to a dropping funnel. Next, this dropping funnel was installed on a separate 500mL reactor containing 100g of 2-butanone, and the 2-butanone was heated to 78°C.

[0301] The temperature of 2-butanone in the reactor was maintained at 78±1°C. Under this condition, and with a nitrogen flow, the above mixed solution was slowly added dropwise to the reactor through a dropping funnel over 2 hours. After the addition was completed, the temperature was maintained at 78±1°C for 6 hours and then cooled. At this time, the temperature was slowly reduced to 30°C over 30 minutes to obtain a fluoropolymer containing repeating units shown in formula (1-1), repeating units shown in formula (2-1), and repeating units shown in formula (12-1). The obtained fluoropolymer is the fluoropolymer of Example 8.

[0302] The molecular weight of the fluorinated copolymer of Example 8, obtained by removing 2-butanone from the reaction solution, was determined by gel permeation chromatography (GPC), and the weight-average molecular weight was 9532 (N=1).

[0303] [Chemical Formula 16]

[0304]

[0305] The reaction solution of the fluoropolymer of Example 8 was prepared five times (N=2-6) in the same manner, for a total of six preparations. The weight-average molecular weight of the fluoropolymer of Example 8 in each preparation was determined. The results are shown in Table 2.

[0306] (Example 9)

[0307] The fluoropolymer of Example 9 was prepared in the same manner as in Example 8, except that raw material composition C was used instead of raw material composition A. The weight-average molecular weight of the fluoropolymer of Example 9 was then determined. The results are shown in Table 2.

[0308] (Comparative Example 1)

[0309] The fluoropolymer of Comparative Example 1 was prepared in the same manner as in Example 1, except that raw material composition F was used instead of raw material composition A. The weight-average molecular weight of the fluoropolymer of Comparative Example 1 was then determined. The results are shown in Table 2.

[0310] (Comparative Example 2)

[0311] The fluoropolymer of Comparative Example 2 was prepared in the same manner as in Example 8, except that raw material composition F was used instead of raw material composition A. The weight-average molecular weight of the fluoropolymer of Comparative Example 2 was then determined. The results are shown in Table 2.

[0312] (The content of repeating units)

[0313] For the fluoropolymers of each embodiment and each comparative example, the contents of the repeating units shown in formula (1-1) and formula (2-1) were determined, and the contents of the repeating units shown in formula (2-1) were calculated in parts per million based on the mass of the repeating units shown in formula (1-1). The results are shown in Table 2.

[0314] In addition, the content of each repeating unit in the polymer as shown in formula (2-1) is determined as follows.

[0315] First, the post-reaction solutions of each example and each comparative example were measured by HPLC to confirm that no monomers used as raw materials remained in the post-reaction solutions.

[0316] Based on this, the polymers of each embodiment and each comparative example 1 H-NMR, 19 F-NMR or 13 The C-NMR values ​​were used to quantify the content of the repeating units represented by formula (2-1) in the polymers of each example and each comparative example.

[0317] [Table 2]

[0318]

[0319] [Solubility in developer and swelling in water - evaluation of solubility]

[0320] The fluoropolymers of each embodiment and each comparative example were dissolved in a mixed solvent of 95% by mass n-heptane and 5% by mass n-hexanol to obtain film-forming solutions with a solid content concentration of 2.5% by mass.

[0321] Next, the various film-forming solutions are spin-coated onto the silicon wafer and baked at 110°C to obtain a uniform resist film.

[0322] These resist films were immersed in a 2.38% by mass aqueous solution of tetramethylammonium hydroxide as the developer and dissolved to evaluate their solubility.

[0323] The presence of residue on the substrate was evaluated using a laser microscope. A Keyence VX-1100 laser microscope was used.

[0324] The results are shown in Table 3.

[0325] The evaluation criteria are as follows.

[0326] ◎: After being immersed in the developer, the film quickly dissolves in the developer and disappears.

[0327] 〇: After immersion in the developing solution, the film dissolves within 60 seconds and disappears.

[0328] ×: After immersing in the developing solution for 60 seconds, the membrane was removed. Although the membrane dissolved, dot-like residues were found in the areas where the membrane was.

[0329] The substrate coated with these resist films was cut in half, and one half was immersed in pure water for 30 minutes. The swelling and dissolution of the film were evaluated by comparing it with the unimmersed substrate.

[0330] The evaluation method is as follows.

[0331] The presence of the aforementioned impregnation was observed on the substrate using a laser microscope for evaluation. A Keyence VX-1100 laser microscope was used.

[0332] The results are shown in Table 3.

[0333] The evaluation criteria are as follows.

[0334] 〇: No swelling or dissolution of the membrane occurred.

[0335] ×: Swelling and dissolution of the membrane occur.

[0336] [Table 3]

[0337]

[0338] As shown in Table 3, the resist films made from the fluoropolymers of Examples 1 to 9 with a low proportion of the repeating unit shown in Formula (2-1) exhibit good solubility in the developer.

[0339] On the other hand, the resist films made from the fluoropolymers of Comparative Examples 1 and 2, which contain a high proportion of repeating units as shown in Formula (2-1), have poor solubility in the developer.

Claims

1. A fluoropolymer characterized in that, contains a repeating unit represented by the following formula (1-1) and a repeating unit represented by the following formula (2-1), the content of the repeating unit represented by the formula (2-1) is 495 ppm or less, 2. The fluoropolymer of claim 1, wherein, the content of the repeating unit represented by the formula (2-1) is 495 ppm or less.

3. The fluoropolymer of claim 1 or 2, wherein, the content of the repeating unit represented by the formula (2-1) is 450 ppm or less.

4. The fluoropolymer of claim 1 or 2, wherein, the content of the repeating unit represented by the formula (2-1) is 200 ppm or less.

5. The fluoropolymer of claim 1 or 2, wherein, the fluorine-containing polymer contains other repeating units in addition to the repeating unit represented by the formula (1-1) and the repeating unit represented by the formula (2-1).

6. The fluoropolymer of claim 5, wherein, the other repeating units are repeating units from other monomers, the other monomers contain at least one selected from the group consisting of a monomer containing an acid-decomposable group, a monomer having a lactone structure, a monomer having a hexafluoroisopropyl alcohol group, acrylic esters, methacrylic esters, fluorine-containing acrylic esters, fluorine-containing methacrylic esters, styrenes, fluorine-containing styrenes, vinyl ethers, fluorine-containing vinyl ethers, allyl ethers, fluorine-containing allyl ethers, unsaturated amides, olefins, fluorine-containing olefins, norbornene compounds, fluorine-containing norbornene compounds, vinyl silanes, vinyl sulfonic acids, vinyl sulfonic acid esters, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and sulfur dioxide.

7. The fluoropolymer of claim 6, wherein, the other monomers contain at least one selected from the group consisting of 3,5-bis(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)cyclohexyl methacrylate and 1,1,2,2-tetrahydroheptadecafluoro-n-decyl acrylate.

8. The fluoropolymer of claim 6 or 7, wherein, the proportion of the repeating units from the other monomers is 1 mol% or more and 80 mol% or less when the total repeating units contained in the fluorine-containing polymer is 100 mol%.

9. The fluoropolymer of claim 6 or 7, wherein, the proportion of the repeating units from the other monomers is 5 mol% or more and 70 mol% or less when the total repeating units contained in the fluorine-containing polymer is 100 mol%.

10. The fluoropolymer of claim 6 or 7, wherein, the proportion of the repeating units from the other monomers is 10 mol% or more and 60 mol% or less when the total repeating units contained in the fluorine-containing polymer is 100 mol%.

11. The fluoropolymer of claim 1 or 2, wherein, the weight average molecular weight of the fluorine-containing polymer is 5000 to 20000.

12. The fluoropolymer of claim 1 or 2, wherein, the weight average molecular weight of the fluorine-containing polymer is 7000 to 12000.

13. The fluoropolymer of claim 1 or 2, wherein, the fluorine-containing polymer is used for a film-forming solution.

14. The fluoropolymer of claim 1 or 2, wherein, the fluorine-containing polymer is used as a component of an upper layer film for protecting a resist film and / or a resist pattern.

15. Use of the fluorine-containing polymer described in any one of claims 1 to 14 as a component of an upper layer film for protecting a resist film and / or a resist pattern.

16. A film-forming solution containing the fluorine-containing polymer described in any one of claims 1 to 14, the solid component concentration in the film-forming solution is 3 mass% or more and 25 mass% or less.

17. The solution for film formation according to claim 16, wherein, the solid component concentration in the film-forming solution is 5 mass% or more and 15 mass% or less.

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