Method for purifying polymer and method for producing resist composition

Abstract

The present invention provides a method for purifying a polymer, with which it is possible to obtain a polymer having a narrow molecular weight distribution in a high yield. This method for purifying a polymer comprises: a step (A) in which, to a polymer solution containing a solvent and a polymer dissolved in the solvent, a poor solvent for the polymer is added to precipitate a part of the polymer, and a mixture containing the precipitate and a mixed solvent containing the solvent and the poor solvent is obtained; and a step (B) in which the precipitate is recovered from the mixture. The absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa0.5 or less.

Description

Polymer purification method and resist composition manufacturing method

[0001] The present invention relates to a method for purifying a polymer and a method for producing a resist composition.

[0002] BACKGROUND ART Reprecipitation is a known method for removing low molecular weight components from a synthesized polymer to obtain a purified polymer having a narrow molecular weight distribution (weight average molecular weight / number average molecular weight).

[0003] Specifically, for example, in Patent Document 1, a copolymer containing α-methylstyrene units and α-methyl chloroacrylate units, which is useful as a positive resist, is dissolved in tetrahydrofuran (THF), which is a good solvent in which the copolymer has high solubility, and then the resulting solution is dropped into methanol, which is a poor solvent in which the copolymer has low solubility, and the precipitated solid is collected by filtration. This procedure is repeated to adjust the molecular weight distribution.

[0004] Japanese Patent Application Laid-Open No. 2020-86062

[0005] However, the above-mentioned conventional technique, in which a polymer solution obtained by dissolving a polymer in a good solvent is dropped into a poor solvent to perform reprecipitation, has a problem in that the molecular weight distribution value cannot be sufficiently narrowed unless reprecipitation is repeated, and a purified polymer having a narrow molecular weight distribution cannot be obtained in high yield.

[0006] Therefore, there has been a demand for a method for purifying a polymer that can produce a polymer with a narrow molecular weight distribution in high yield.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that when purifying a polymer using a reprecipitation method, a purified polymer with a narrow molecular weight distribution can be obtained in high yield by adding a poor solvent to a polymer solution in an amount that satisfies specific conditions, rather than by dissolving the polymer in a good solvent and dropping the resulting polymer solution into a poor solvent, and that the use of such a purification method can efficiently produce a resist composition that exhibits excellent pattern formability, thereby completing the present invention.

[0008] That is, an object of the present invention is to advantageously solve the above-mentioned problems, and [1] a method for purifying a polymer of the present invention includes a step (A) of adding a poor solvent for the polymer to a polymer solution containing a solvent and a polymer dissolved in the solvent to precipitate a part of the polymer, thereby obtaining a mixture containing the precipitate and a mixed solvent containing the solvent and the poor solvent, and a step (B) of recovering the precipitate from the mixture, wherein the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa. ０．５ Here, the SP value (δ) is the Hansen solubility parameter (δ ｄ , δ ｐ , δ ｈ ) and is expressed by the following formula (1): ２ = (δ ｄ ) ２ + (δ ｐ ) ２ + (δ ｈ ) ２ ...(1) [In formula (1), δ ｄ represents the dispersion term (also called the London dispersion term), and δ ｐ represents the polar term (also called the molecular polarization term), and δ ｈ represents the hydrogen bond term. ｄ , δ ｐ and δ ｈ By using HSPiP (Hansen Solubility Parameters in Practice), a program developed by the group of Dr. Hansen, who proposed the Hansen solubility parameters, the Hansen solubility parameters can be easily estimated from the chemical structure of a substance even if the literature values ​​are unknown. In this specification, for substances registered in the database, the values ​​are used, and for substances not registered, estimated values ​​using HSPiP version 5.4 are used, and δ ｄ , δ ｐ and δ ｈ In addition, δ of a mixture of multiple substances is calculated. ｄ , δ ｐ and δ ｈare the δ of each substance contained in the mixture ｄ , δ ｐ and δ ｈ The δ of the polymer is calculated by multiplying the δ by the content (mass basis) of the substance. ｄ , δ ｐ and δ ｈ are the δ of the monomers used to form the structural units contained in the polymer, respectively. ｄ , δ ｐ and δ ｈ is multiplied by the content (by mass) of the constituent unit and the sum is calculated.

[0009]

[0023] Here, the method for purifying a polymer of the present invention [2] is preferably the method for purifying a polymer according to the above [1], wherein the weight-average molecular weight of the precipitate is 130,000 or more and 240,000 or less. In the present invention, the "weight-average molecular weight" can be measured using gel permeation chromatography.

[0010] [3] The method for purifying a polymer according to the present invention is preferably the method for purifying a polymer according to the above [1] or [2], wherein the proportion of components having a molecular weight of 24,000 or less in the precipitate is 1.34% or less in terms of area ratio measured by gel permeation chromatography. In the present invention, the "proportion of components having a molecular weight of 24,000 or less" can be determined by calculating the ratio (B) of the sum of the peak areas of components having a molecular weight of 24,000 or less to the total peak area (A) from a chromatogram obtained using gel permeation chromatography.

[0011] Furthermore, [4] the method for purifying a polymer of the present invention is preferably the method for purifying a polymer according to any one of the above [1] to [3], wherein the solvent is at least one selected from the group consisting of ethers, ketones, and esters.

[0012] [5] The method for purifying a polymer of the present invention is preferably the method for purifying a polymer according to any one of the above [1] to [4], wherein the poor solvent is at least one selected from the group consisting of alcohols, aliphatic hydrocarbons, and water.

[0013] Furthermore, [6] the method for purifying a polymer of the present invention is characterized in that the polymer is a polymer represented by the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.

[0014] [7] The method for purifying a polymer of the present invention is preferably the method for purifying a polymer according to any one of the above [1] to [6], wherein the proportion of the solvent in the mixed solvent is 10% by mass or more and 40% by mass or less.

[0015] Furthermore, [8] the method for purifying a polymer of the present invention, ０．５ Over 27.0 MPa ０．５ The method for purifying a polymer according to any one of the above items [1] to [7] is preferred.

[0016] [9] A method for producing a resist composition of the present invention is characterized by comprising the steps of purifying a polymer using the method for purifying a polymer according to any one of the above items [1] to [8], and preparing a resist composition using the purified polymer.

[0017] According to the method for purifying a polymer of the present invention, a polymer having a narrow molecular weight distribution can be obtained in high yield.

[0018] The present invention will be described in detail below. The polymer purification method of the present invention can be used to remove low-molecular-weight components from a polymer to obtain a purified polymer. The polymer purification method of the present invention is not particularly limited, and can be suitably used to purify a polymer that can be used as a resist and produce a resist composition.

[0019] (Polymer Purification Method) The polymer purification method of the present invention includes a step (A) of adding a poor solvent for the polymer to a polymer solution containing a solvent and a polymer dissolved in the solvent to precipitate a part of the polymer, thereby obtaining a mixture containing the precipitate and a mixed solvent containing the solvent and the poor solvent, and a step (B) of recovering the precipitate from the mixture. In the polymer purification method of the present invention, the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa. ０．５ It is necessary to add an anti-solvent so that:

[0020] In this way, a poor solvent is added to the polymer solution, and the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa. ０．５ If the following conditions are met, low molecular weight polymers can be effectively removed, and a purified polymer having a narrower molecular weight distribution than the polymer contained in the polymer solution can be obtained in high yield.

[0021] <Step (A)> In step (A), a poor solvent is added to a polymer solution containing a solvent and a polymer to precipitate a part of the polymer, thereby obtaining a mixture containing the precipitate and the mixed solvent.

[0022] [Polymer Solution] Here, the polymer solution contains a solvent and a polymer dissolved in the solvent, and may further contain other components as desired.

[0023] The polymer concentration in the polymer solution is not particularly limited, and is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, and more preferably 25% by mass or less. When the polymer concentration is equal to or less than the upper limit, it is easy to remove low-molecular-weight components. When the polymer concentration is equal to or more than the lower limit, it is possible to suppress an increase in the amount of poor solvent used and reduce the cost required for purifying the polymer.

[0024] The solvent is not particularly limited as long as it can dissolve the polymer, and any solvent can be used. Specifically, the solvent may be one in which the solubility of the polymer at a temperature of 25° C. is 5 g / 100 g or more.

[0025] The solvent is not particularly limited, and at least one selected from the group consisting of ethers such as diethyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, cyclohexanone, diisobutyl ketone, and cyclopentanone; and esters such as ethyl acetate, butyl acetate, ethyl propionate, and butyl propionate can be used.

[0026] Among these, from the viewpoint of the solubility of the polymer, the ethers are preferably cyclic ethers, and more preferably tetrahydrofuran; the ketones are preferably acetone and cyclopentanone; and the esters are preferably acetate esters and propionate esters, and more preferably acetate esters, and even more preferably ethyl acetate.

[0027] -Polymer- The polymer is not particularly limited, and examples thereof include acrylic polymers such as polymethyl methacrylate; diene polymers such as polybutadiene, polyisoprene, styrene-butadiene polymer (SBR), styrene-butadiene-styrene block polymer (SBS), styrene-isoprene polymer, styrene-isoprene-styrene block polymer (SIS), and acrylonitrile-butadiene polymer (NBR), and hydrogenated products thereof; cyclic olefin polymers such as cyclic olefin copolymer (COC) and cyclic olefin polymer (COP), and hydrogenated products thereof; and other polymers.

[0028] In the present invention, "acrylic polymer" refers to a polymer having the highest content of (meth)acrylic acid ester units among all repeating units constituting the polymer. Furthermore, "diene polymer" refers to a polymer having the highest content of structural units derived from aliphatic conjugated dienes among all repeating units constituting the polymer. Furthermore, "cyclic olefin polymer" refers to a polymer having the highest content of structural units derived from cyclic olefins among all repeating units constituting the polymer. Here, "(meth)acrylic acid ester" refers to acrylic acid ester and / or methacrylic acid ester. Furthermore, "structural units derived from" a certain monomer include not only monomer units formed upon polymerization of the monomer, but also structural units formed by hydrogenating or crosslinking the formed monomer units.

[0029] Among these, the polymer is preferably a polymer that can be used as a positive resist, and more preferably a polymer that can be used as a main chain scission type positive resist, in which the main chain is scissed by irradiation with ionizing radiation such as an electron beam or short wavelength light such as ultraviolet light (including extreme ultraviolet light (EUV)), thereby increasing the solubility in a developer.

[0030] Here, examples of polymers that can be used as main chain scission type positive resists include those represented by the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or an alkyl group substituted with a fluorine atom, and may be the same or different from each other.] A polymer containing a monomer unit (I) derived from a monomer represented by the above formula (I) and a monomer unit (I) derived from a monomer represented by the following formula (II): [In formula (II), R ５ , R ７ and R ８ are each independently a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other; R ６is an organic group or a halogen atom, and n is an integer of 0 to 5.] is more preferred.

[0031] Among these, polymers that can be used as main chain scission type positive resists include those containing at least one monomer unit selected from the group consisting of methyl α-chloroacrylate unit, ethyl α-chloroacrylate unit, benzyl α-chloroacrylate unit, 1-adamantyl α-chloroacrylate unit, 2,2,3,3,3-pentafluoropropyl α-chloroacrylate unit, 2,2,3,3,4,4,4-heptafluorobutyl α-chloroacrylate unit, 1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl α-chloroacrylate unit, 2,2,3,3,3-pentafluoropropyl α-chloroacrylate unit, and 2,2,3,3,4,4,5,5,5-nonafluoropentyl α-chloroacrylate unit, １ is a chlorine atom and R ３ and R ４ is a hydrogen atom, and a monomer unit derived from at least one monomer selected from the group consisting of α-methylstyrene (AMS) and its derivatives (e.g., the following monomers (c-1) to (c-10)). ５ is a methyl group and R ７ and R ８ is preferably a polymer containing a repeating unit represented by the above formula (II) in which R is a hydrogen atom.

[0032] Here, without any particular limitation, the SP value of the polymer is 15.0 MPa １／２ Over 25.0 MPa １／２ It is preferable that the pressure is 15.0 MPa or less. １／２ Over 20.0 MPa １／２ More preferably, it is:

[0033] Furthermore, without being particularly limited, the weight average molecular weight of the polymer may be 50,000 or more, 80,000 or more, 150,000 or more, 250,000 or less, 220,000 or less, or 200,000 or less.

[0034] Furthermore, the molecular weight distribution (dispersity) of the polymer is not particularly limited, and may be 1.8 or more, 2.2 or more, 2.3 or more, 2.5 or less, or 2.4 or less. In the present invention, the "molecular weight distribution" can be calculated from the weight average molecular weight and number average molecular weight measured using gel permeation chromatography.

[0035] The proportion of components having a molecular weight of 24,000 or less contained in the polymer may be 2.00% or more and 10.0% or less in terms of area ratio in gel permeation chromatography measurement.

[0036] The above-mentioned polymers are not particularly limited and can be prepared by known methods such as emulsion polymerization, suspension polymerization, and solution polymerization.

[0037] The polymer solution may be prepared by using the reaction liquid obtained by the polymerization reaction as it is, or by recovering the polymer from the reaction liquid and dissolving the polymer again in a solvent.

[0038] [Poor Solvent] The poor solvent is not particularly limited as long as it can precipitate a part of the polymer from the polymer solution, and any liquid can be used. Specifically, the poor solvent can be a liquid in which the solubility of the polymer at a temperature of 25° C. is less than 5 g / 100 g.

[0039] The poor solvent is not particularly limited, and at least one selected from the group consisting of alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, and hexanol; aliphatic hydrocarbons such as hexane, heptane, cyclopentane, and cyclohexane; and water can be used.

[0040] Among these, from the viewpoint of favorably precipitating a portion of the polymer from the polymer solution, the alcohols are preferably alcohols having 5 or less carbon atoms, and more preferably methanol and isopropyl alcohol; and the aliphatic hydrocarbons are preferably saturated aliphatic hydrocarbons, more preferably saturated aliphatic hydrocarbons having 8 or less carbon atoms, and even more preferably hexane and heptane.

[0041] [Addition] The addition of the poor solvent to the polymer solution is not particularly limited, but can be carried out by adding the poor solvent to the polymer solution while stirring. Here, the poor solvent is preferably added over a period of time of, for example, 0.1 to 3 hours.

[0042] The temperature at which the poor solvent is added to the polymer solution is preferably 0° C. or higher, more preferably 5° C. or higher, and is preferably 100° C. or lower, more preferably 50° C. or lower.

[0043] After the poor solvent is added, it is preferable to further stir the mixture for, for example, 0.5 to 3 hours, and heating and / or cooling may be carried out during stirring after the poor solvent is added.

[0044] The amount of the poor solvent to be added is preferably 60% by mass or more, more preferably 70% by mass or more, and is preferably 90% by mass or less, and more preferably 85% by mass or less, where the total of the amount of the solvent in the polymer solution and the amount of the poor solvent added is 100% by mass.

[0045] [Mixture] The mixture obtained by adding a poor solvent to a polymer solution to precipitate a portion of the polymer contains the precipitate, the mixed solvent, and the polymer that did not precipitate.

[0046] In the method for purifying a polymer of the present invention, a poor solvent is added to a polymer solution. When a poor solvent is added to a polymer solution, precipitation usually occurs gradually, starting with components with higher molecular weights. Therefore, the precipitate usually consists of a purified polymer with a narrow molecular weight distribution in which the content of low molecular weight components is reduced.

[0047] The weight-average molecular weight of the precipitate will usually be larger than the weight-average molecular weight of the polymer contained in the polymer solution, and is preferably 100,000 or more, more preferably 130,000 or more, even more preferably 180,000 or more, and preferably 300,000 or less, more preferably 250,000 or less, and even more preferably 240,000 or less. If the weight-average molecular weight of the precipitate is within the above range, the pattern formability of a resist composition prepared using the precipitate can be improved, particularly when the polymer is a polymer that can be used as a main-chain scission-type positive resist.

[0048] Furthermore, the molecular weight distribution (dispersity) of the precipitate will usually be smaller than the molecular weight distribution of the polymer contained in the polymer solution, and is preferably 1.6 or more, more preferably 1.7 or more, and preferably 2.1 or less, and more preferably 2.0 or less. If the molecular weight distribution of the precipitate is within the above range, the pattern formability of a resist composition prepared using the precipitate can be improved, particularly when the polymer is a polymer that can be used as a main chain scission type positive resist.

[0049] Furthermore, the proportion of components having a molecular weight of 24,000 or less contained in the precipitate is usually lower than the proportion of components having a molecular weight of 24,000 or less contained in the polymer contained in the polymer solution, and is preferably 1.34% or less, and more preferably 1.30% or less, in terms of area ratio measured by gel permeation chromatography. If the proportion of components having a molecular weight of 24,000 or less is equal to or less than the above upper limit, the pattern formability of a resist composition prepared using the precipitate can be improved, particularly when the polymer is a polymer that can be used as a main chain scission type positive resist. Note that there is no particular limitation on the lower limit of the proportion of components having a molecular weight of 24,000 or less contained in the precipitate.

[0050] - Mixed Solvent - The mixed solvent contains the solvent contained in the polymer solution and a poor solvent. In the method for purifying a polymer of the present invention, the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa. ０．５The absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent must be 10.0 MPa or less. ０．５ If the content of low molecular weight components in the precipitate is sufficiently reduced, a precipitate consisting of a purified polymer with a narrow molecular weight distribution can be obtained. From the viewpoint of further reducing the content of low molecular weight components in the precipitate and further narrowing the molecular weight distribution, the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 9.0 MPa or less. ０．５ The lower limit of the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is not particularly limited.

[0051] The mixed solvent has an SP value of 15.0 MPa. ０．５ Over 27.0 MPa ０．５ If the SP value of the mixed solvent is within the above range, the precipitate can be favorably precipitated.

[0052] The proportion of the solvent contained in the polymer solution in the mixed solvent is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 40% by mass or less, and more preferably 30% by mass or less. If the proportion of the solvent is equal to or greater than the lower limit, the proportion of low molecular weight components can be further reduced, and a purified polymer having a narrower molecular weight distribution can be obtained. If the proportion of the solvent is equal to or less than the upper limit, the yield of the purified polymer obtained can be further increased.

[0053] <Step (B)> In step (B), a precipitate is recovered from the mixture obtained in step (A). Here, the recovery of the precipitate is not particularly limited, and can be carried out using a known solid-liquid separation method such as centrifugation or filtration. Among these, from the viewpoint of efficiently recovering the precipitate, it is preferable to recover the precipitate by filtering the mixture.

[0054] The recovered precipitate may be optionally subjected to post-treatment such as drying.

[0055] (Method for Producing Resist Composition) The method for producing a resist composition of the present invention includes the steps of purifying a polymer using the above-mentioned method for purifying a polymer of the present invention, and preparing a resist composition using the purified polymer obtained. In this way, by using the purified polymer obtained using the method for purifying a polymer of the present invention, it is possible to obtain a resist composition that has excellent pattern formability and is capable of forming a resist film that has excellent local dimensional uniformity and few defects.

[0056] Here, the resist composition is not particularly limited, and can be prepared by mixing the precipitate, which is the purified polymer, with a solvent and other components that are optionally used. The mixing method is not particularly limited, and mixing can be performed by a known method. Alternatively, the resist composition can be prepared by mixing the components and then filtering the mixture.

[0057] The solvent is not particularly limited, and known solvents such as isoamyl acetate can be used.

[0058] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. In the following examples and comparative examples, various measurements and evaluations were carried out by the following methods.

[0059] <Number Average Molecular Weight, Weight Average Molecular Weight, and Molecular Weight Distribution> 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. Specifically, a gel permeation chromatograph (HLC-8420, manufactured by Tosoh Corporation) was used with tetrahydrofuran as the developing solvent to determine the number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer in terms of standard polystyrene. The molecular weight distribution (Mw / Mn) was then calculated. <Proportion of Components of Each Molecular Weight in the Polymer> A gel permeation chromatograph (HLC-8420, manufactured by Tosoh Corporation) was used with tetrahydrofuran as the developing solvent to obtain a chromatogram of the polymer. From the obtained chromatogram, the total area of ​​the peaks (A) and the sum of the areas of the peaks of components having a molecular weight of 24,000 or less (B) were then calculated. The proportion of the components of each molecular weight was then calculated using the following formula. Proportion (%) of components with a molecular weight of 24,000 or less = (B / A) × 100 <Pattern Formability> E2Stack (registered trademark) AL412 (manufactured by Brewer Science, Inc.) was applied to a silicon substrate using a coater developer (DT-3000, manufactured by SCREEN) and dried at 220°C for 60 seconds to form a 5 nm thick EUV assist layer. Thereafter, the prepared positive resist composition was applied to the EUV assist layer using the coater developer and dried at 170°C for 60 seconds to form a 40 nm thick resist film. The resulting resist film was exposed to light using an EUV exposure system (NXE3400B, manufactured by ASML) through a mask with a 40 nm pitch and a 25 nm hole diameter. The resist film was then developed using isopropyl alcohol at 23°C for 30 seconds and dried to obtain a resist film with a contact hole pattern formed thereon. Then, 40,000 contact holes in the resist film on which the contact hole pattern was formed were evaluated for LCDU (Local Critical Dimension Uniformity) and defects using a CD-SEM (Hitachi CG6300). Specifically, the LCDU was calculated as three times the standard deviation of the observed hole diameters and evaluated as the LCDU. A smaller value indicates better performance.Furthermore, for defects, pattern recognition was performed using built-in software, and those that could not be measured as holes were determined to be defects and the number of such defects was counted.

[0060] Example 1 [Polymer Preparation] 10.00 g of α-chloroacrylate-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl ester and 3.55 g of α-methylstyrene as monomers, 22.09 g of ultrapure water as a reaction solvent, 3.39 g of sodium laurate as soap (emulsifier), and 0.0987 g of azobisisobutyronitrile as a polymerization initiator were placed in a glass container, the glass container was sealed and purged with nitrogen, and the mixture was stirred in a nitrogen atmosphere in a thermostatic bath at 75°C for 3 hours. The temperature was then returned to room temperature, and the glass container was opened to the atmosphere. Then, 18.4 g of tetrahydrofuran (THF) was added to the resulting polymer solution to precipitate a viscous solid. The supernatant was then removed, and 65.1 g of THF was added. The viscous solid was redissolved in the solution, which was then added dropwise to 383 g of methanol to precipitate a polymer. The solution containing the precipitated polymer was then filtered using a Kiriyama funnel to obtain a white coagulum (polymer A). The obtained polymer A had a number average molecular weight (Mn) of 72,000, a weight average molecular weight (Mw) of 172,000, a molecular weight distribution (Mw / Mn) of 2.40, and a proportion of components having a molecular weight of 24,000 or less of 5.96%. [Preparation of polymer solution] 10 g of the obtained polymer A was dissolved in 125 g of tetrahydrofuran as a solvent to prepare a polymer solution. [Step (A)] 265 g of methanol (MeOH) as a poor solvent was added dropwise to 135 g of the obtained polymer solution to precipitate a solid (solid concentration 2.5% by mass, THF / MeOH (mass ratio) = 32 / 68). [Step (B)] The solution (mixture) containing the precipitated solids was then filtered using a Kiriyama funnel and then dried, yielding a precipitate (purified polymer) consisting of a white coagulated substance (8.5 g, yield: 85%). The weight-average molecular weight, molecular weight distribution, and proportion of components with a molecular weight of 24,000 or less of the precipitate were then measured. The results are shown in Table 1. [Preparation of Resist Composition] The obtained precipitate was dissolved in isoamyl acetate as a solvent, and the polymer concentration was adjusted to 1.75% by mass. The resulting solution was then passed through a filter (manufactured by Entegris, material: polyethylene (ultra-high molecular weight polyethylene), pore size: 5 nm) to prepare a resist solution (positive resist composition). Pattern formability was then evaluated. The results are shown in Table 1.

[0061] Example 2 The procedure was the same as in Example 1 except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 62 g of tetrahydrofuran as a solvent, and when performing step (A), 328 g of isopropyl alcohol (IPA) as a poor solvent was added dropwise to 72 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, THF / IPA (mass ratio) = 16 / 84), thereby obtaining a precipitate (purified polymer) consisting of a white coagulate (8.1 g, yield: 81%). Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0062] Example 3 The procedure was the same as in Example 1 except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 70 g of acetone as a solvent, and when performing step (A), 320 g of isopropyl alcohol as a poor solvent was added dropwise to 80 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, acetone / IPA (mass ratio) = 18 / 82), thereby obtaining a precipitate (purified polymer) consisting of a white coagulate (8.4 g, yield: 84%). Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0063] Example 4 The procedure was the same as in Example 1 except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 94 g of ethyl acetate as a solvent, and, when performing step (A), 296 g of isopropyl alcohol was added dropwise as a poor solvent to 104 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, ethyl acetate / IPA (mass ratio) = 24 / 76), thereby obtaining a precipitate (purified polymer) consisting of a white coagulate (8.2 g, yield: 82%). Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0064] Example 5 The same procedures as in Example 1 were carried out except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 78 g of tetrahydrofuran as a solvent, and, when carrying out step (A), 312 g of hexane as a poor solvent was added dropwise to 88 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, THF / hexane (mass ratio) = 20 / 80), thereby obtaining a precipitate (purified polymer) consisting of a white coagulate (8.5 g, yield: 85%). Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0065] Example 6 The procedure was the same as in Example 1 except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 59 g of tetrahydrofuran as a solvent, and when performing step (A), 332 g of a mixed solvent of water and isopropyl alcohol (water / IPA = 59 g / 273 g) was added dropwise as a poor solvent to 69 g of the resulting polymer solution to precipitate solids (solid concentration 2.5 mass %, THF / water / IPA (mass ratio) = 15 / 15 / 70). A precipitate (purified polymer) consisting of a white coagulated substance was obtained (8.4 g, yield: 84%). A resist composition was also prepared in the same manner as in Example 1. Measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0066] Example 7 During the preparation of the polymer, the amount of azobisisobutyronitrile added as a polymerization initiator was changed to 0.3388 g, and a polymer A' was prepared having a number average molecular weight (Mn) of 44,000, a weight average molecular weight (Mw) of 98,000, a molecular weight distribution (Mw / Mn) of 2.25, and a proportion of components having a molecular weight of 24,000 or less of 9.53%. A precipitate (purified polymer) consisting of a white coagulated substance was obtained in the same manner as in Example 1, except that polymer A' was used instead of polymer A (8.0 g, yield: 80%). A resist composition was also prepared in the same manner as in Example 1. Measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0067] Example 8 During the preparation of the polymer, the amount of azobisisobutyronitrile added as a polymerization initiator was changed to 0.0148 g, and a polymer A" was prepared. The number average molecular weight (Mn) was 121,000, the weight average molecular weight (Mw) was 220,000, the molecular weight distribution (Mw / Mn) was 1.82, and the proportion of components having a molecular weight of 24,000 or less was 2.20%. A precipitate (purified polymer) consisting of a white coagulate was obtained in the same manner as in Example 1, except that polymer A" was used instead of polymer A (8.8 g, yield: 88%). A resist composition was also prepared in the same manner as in Example 1. Measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0068] Example 9 [Preparation of Polymer] 10.00 g of 2,2,3,3,3-pentafluoropropyl α-chloroacrylate and 5.63 g of 4-hydroxy-α-methylstyrene as monomers, 62.52 g of cyclopentanone as a reaction solvent, and 0.0026 g of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) as a polymerization initiator were placed in a glass container, and the glass container was sealed and purged with nitrogen. The mixture was stirred in a nitrogen atmosphere in a thermostatic chamber at 23°C for 72 hours. Thereafter, the glass container was opened to the atmosphere, and the resulting polymerization solution was added dropwise to 782 g of heptane to precipitate a polymer. Thereafter, the solution containing the precipitated polymer was filtered using a Kiriyama funnel to obtain a white coagulum (Polymer B). The number average molecular weight (Mn) of the obtained polymer B was 79,000, the weight average molecular weight (Mw) was 182,000, the molecular weight distribution (Mw / Mn) was 2.30, and the proportion of components having a molecular weight of 24,000 or less was 5.31%. [Preparation of polymer solution] 10 g of the obtained polymer B was dissolved in 117 g of cyclopentanone as a solvent to prepare a polymer solution. [Step (A)] 273 g of heptane as a poor solvent was added dropwise to 127 g of the obtained polymer solution to precipitate solids (solid concentration 2.5 mass%, cyclopentanone / heptane (mass ratio) = 30 / 70). [Step (B)] The solution (mixture) containing the precipitated solids was then filtered using a Kiriyama funnel and then dried to obtain a precipitate (purified polymer) consisting of a white coagulum (8.5 g, yield: 85%). The weight average molecular weight, molecular weight distribution, and proportion of components with a molecular weight of 24,000 or less of the precipitate were then measured. The results are shown in Table 1. [Preparation of Resist Composition] The obtained precipitate was dissolved in isoamyl acetate as a solvent, and the polymer concentration was adjusted to 1.75 mass %. The resulting solution was then passed through a filter (manufactured by Entegris, material: polyethylene (ultra-high molecular weight polyethylene), pore size: 5 nm) to prepare a resist solution (positive resist composition). Pattern formability was then evaluated. The results are shown in Table 1.

[0069] Comparative Example 1 The procedure of Example 1 was repeated except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 20 g of tetrahydrofuran as a solvent, and, when performing step (A), 371 g of methanol as a poor solvent was added dropwise to 30 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, THF / MeOH (mass ratio) = 5 / 95). A precipitate (purified polymer) consisting of a white coagulate was obtained (9.5 g, yield: 95%). A resist composition was prepared in the same manner as in Example 1. Measurements and evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 1.

[0070] Comparative Example 2 The same procedures as in Example 1 were carried out except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 59 g of tetrahydrofuran as a solvent, and when performing step (A), 332 g of methanol as a poor solvent was added dropwise to 69 g of the obtained polymer solution to precipitate a solid (solid concentration: 2.5 mass %, THF / MeOH (mass ratio) = 15 / 85), thereby obtaining a precipitate (purified polymer) consisting of a white coagulate (9.1 g, yield: 91%). Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0071] Comparative Example 3 The procedure of Example 1 was repeated except that, when preparing the polymer solution, 10 g of polymer A was dissolved in 59 g of tetrahydrofuran as a solvent, and, when performing step (A), 332 g of a mixed solvent of water and isopropyl alcohol (water / IPA = 98 g / 234 g) was added dropwise as a poor solvent to 69 g of the resulting polymer solution to precipitate solids (solid concentration: 2.5 mass %, THF / water / IPA (mass ratio) = 15 / 25 / 60). A precipitate (purified polymer) consisting of a white coagulated substance was obtained (9.4 g, yield: 94%). A resist composition was also prepared in the same manner as in Example 1. Measurements and evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0072] Comparative Example 4 In preparing the polymer solution, 10 g of polymer A was dissolved in 125 g of tetrahydrofuran as a solvent, and instead of step (A), step (A') was performed in which 135 g of the obtained polymer solution was dropped into 265 g of methanol as a poor solvent to precipitate a solid (solid concentration: 2.5 mass %, THF / MeOH (mass ratio) = 32 / 68). Except for this, a precipitate (purified polymer) consisting of a white coagulate was obtained (8.6 g, yield: 86%) in the same manner as in Example 1. Furthermore, a resist composition was prepared in the same manner as in Example 1. Then, measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0073] Comparative Example 5: 8 g of the precipitate obtained in Comparative Example 4 was dissolved in 100 g of tetrahydrofuran as a solvent to obtain a polymer solution. Then, 108 g of the obtained polymer solution was added dropwise to 212 g of methanol as a poor solvent to precipitate solids (solid concentration 2.5%, THF / MeOH (mass ratio) = 32 / 68). The solution (mixture) containing the precipitated solids was then filtered using a Kiriyama funnel and dried to obtain a precipitate (purified polymer) consisting of a white coagulated substance (6.88 g, yield: 74% (= {(yield of Comparative Example 4 / 100) × (6.88 g / 8 g)} × 100 (%)). The weight-average molecular weight, molecular weight distribution, and proportion of components with a molecular weight of 24,000 or less of the precipitate were measured. The results are shown in Table 1.

[0074]

[0075] According to the method for purifying a polymer of the present invention, a polymer having a narrow molecular weight distribution can be obtained in high yield.

Claims

1. A method for producing a polymer solution comprising a solvent and a polymer dissolved in the solvent, and a step (A) of adding a poor solvent for the polymer to the polymer solution to precipitate a part of the polymer, thereby obtaining a mixture containing the precipitate and a mixed solvent containing the solvent and the poor solvent; and a step (B) of recovering the precipitate from the mixture, wherein the absolute value of the difference between the SP value of the polymer and the SP value of the mixed solvent is 10.0 MPa. ０．５ A method for purifying a polymer, comprising:

2. The method for purifying a polymer according to claim 1, wherein the weight average molecular weight of the precipitate is 130,000 or more and 240,000 or less.

3. The method for purifying a polymer according to claim 1, wherein the proportion of components having a molecular weight of 24,000 or less in the precipitate is 1.34% or less in terms of area ratio as measured by gel permeation chromatography.

4. The method for purifying a polymer according to claim 1, wherein the solvent is at least one selected from the group consisting of ethers, ketones and esters.

5. The method for purifying a polymer according to claim 1, wherein the poor solvent is at least one selected from the group consisting of alcohols, aliphatic hydrocarbons and water.

6. The polymer has the following formula (I): [In formula (I), R １ is a halogen atom or an alkyl group substituted with a halogen atom, and R ２ is an organic group, and R ３ and R ４ and each independently represent a hydrogen atom, a fluorine atom, an unsubstituted alkyl group, or a fluorine-substituted alkyl group, and may be the same or different from each other.

7. The method for purifying a polymer according to claim 1, wherein the proportion of the solvent in the mixed solvent is 10% by mass or more and 40% by mass or less.

8. The SP value of the mixed solvent is 15.0 MPa ０．５ Over 27.0 MPa ０．５ 2. The method for purifying a polymer according to claim 1, wherein:

9. A method for producing a resist composition, comprising: a step of purifying a polymer using the method for purifying a polymer according to any one of claims 1 to 8; and a step of preparing a resist composition using the purified polymer obtained.

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