JP5640787B2 - Method for producing polymer - Google Patents

Description

The invention also relates to a structural unit having acetal skeleton, the polymer manufacturing how containing a structural unit having a polar group.

In recent years, in the field of microfabrication in the manufacture of semiconductor elements and liquid crystal elements, miniaturization has rapidly progressed due to advances in lithography technology. As a method for miniaturization, generally, a shorter wavelength of irradiation light is used. Specifically, from conventional ultraviolet rays typified by g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm) to DUV ( The irradiation light is changing to Deep Ultra Violet).
At present, KrF excimer laser (wavelength: 248 nm) lithography technology is introduced into the market, and ArF excimer laser (wavelength: 193 nm) lithography technology for further shortening the wavelength is also introduced. Further, as a next-generation technique, an F ₂ excimer laser (wavelength: 157 nm) lithography technique has been studied. In addition, as a slightly different type of lithography technology, an electron beam lithography technology and an EUV lithography technology using extreme ultraviolet light (Extreme Ultra Light Light: EUV light) in the vicinity of 13.5 nm wavelength are also energetically studied. .

A “chemically amplified resist” containing a photoacid generator has been proposed as a high-resolution resist that can handle such short-wavelength irradiation light or electron beams, and improvements and development of this chemically amplified resist are currently underway. Is underway.
As resist materials having excellent transparency to short-wavelength light, many polymers using (meth) acrylic acid derivatives as monomers have been developed, and generally for the purpose of imparting substrate adhesion Monomer having a lactone skeleton, an acid-releasable monomer for the purpose of enhancing solubility in a developing solution by being decomposed by an acid derived from a photoacid generator, or a monomer having a polar group for the purpose of imparting rectangularity The copolymer using the body is manufactured.

In general, in a method for producing a polymer in a solution, the polymer solution obtained by polymerizing monomers in the solution contains unreacted monomers and low molecular weight substances. Purification is performed by mixing the polymer solution with a poor solvent to precipitate the polymer.
Patent Document 1 proposes a copolymer of a monomer having a lactone skeleton, a monomer having an acetal skeleton as an acid-eliminating monomer, and a monomer having a hydroxyl group as a monomer having a polar group The polymer solution is mixed with n-heptane for the purpose of removing unreacted monomers and produced low molecular weight substances from the polymer solution obtained by carrying out the copolymerization reaction in the solution. It is described that the polymer is precipitated (Patent Document 1).

However, when a nonpolar solvent as described in Patent Document 1 is used, if a monomer having a polar group remains, the solubility in heptane, which is a nonpolar solvent, is insufficient. May not be sufficiently removed.
In order to solve this problem, a method of precipitating a polymer using a polar solvent such as alcohol can be considered, but a part of the acetal skeleton in the polymer may be decomposed.
For example, Patent Document 2 discloses a recovery solvent for precipitating and recovering a polymer from a polymer solution obtained by a solution polymerization method when a resist polymer having an acetal structure in which an acid leaving group is produced. As described above, when a solvent having a large solubility parameter such as methanol or water is used, the acetal structure may be decomposed to generate carboxylic acid in the polymer (paragraph [0008]). .
When the carboxylic acid is generated in the polymer, when the polymer is used in a resist composition, an unexpected reaction occurs between the carboxylic acid and the acid labile group, resulting in deterioration of resist performance. There is.

JP 2006-227160 A JP 2006-131739 A

  The present invention has been made in view of the above circumstances, and at least a monomer having an acetal skeleton, a monomer having a lactone ring, and a monomer having a polar group are copolymerized to produce a polymer. An object of the present invention is to provide a polymer production method capable of precipitating and purifying a polymer in a polymer solution while suppressing decomposition of an acetal skeleton, and a polymer obtained by the production method. And

  In the method for producing a polymer by copolymerizing a monomer having an acetal skeleton, a monomer having a lactone ring, and a monomer having a polar group, the polar group is other than a hydroxyl group. If it is a polar group, even if the polymer is precipitated using an alcohol as a poor solvent, it was found that the decomposition of the acetal skeleton can be suppressed, and the present invention has been achieved.

  That is, the method for producing a polymer of the present invention has at least a monomer (A) represented by the following general formula (1), a monomer (B) having a lactone ring, and a polar group other than a hydroxyl group. A polymerization step for copolymerizing the monomer (C), and a polymer solution containing the polymer obtained in the polymerization step is mixed with a poor solvent to precipitate the polymer in the polymer solution. And the poor solvent is an alcohol having a water content of less than 10% by mass.

(In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or a linear or branched hydrocarbon group having 1 to 6 carbon atoms, and R ₃ has 1 to 12 carbon atoms. linear, a branched, or alicyclic hydrocarbon group.)

According to the present invention, in a method for producing a polymer by copolymerizing at least a monomer having an acetal skeleton, a monomer having a lactone ring, and a monomer having a polar group, the decomposition of the acetal skeleton The polymer in the polymer solution can be precipitated and purified while suppressing.
The polymer produced by the method of the present invention is well suppressed in the generation of impurities such as carboxylic acid resulting from the decomposition of the acetal skeleton, and can be suitably used for resist applications, for example.

  Hereinafter, the present invention will be described in detail. In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid.

<Monomer (A)>
The monomer (A) in the present invention is a compound having an acetal skeleton represented by the above formula (1). The monomer (A) is decomposed by an acid derived from a photoacid generator to generate a carboxy group. A monomer (A) may be used individually by 1 type, and may use 2 or more types together.
In the formula (1), R ₁ represents a hydrogen atom or a methyl group.
In the formula (1), R ₂ represents a hydrogen atom or a linear, branched or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, cyclopentyl group, neopentyl group, 1-methylbutyl. Group, 2-methylbutyl group, 3-methylbutyl group, 1,2-dimethylpropyl group, n-hexyl group, cyclohexyl group and the like. Among these, R ₂ is preferably a hydrogen atom or a methyl group from the viewpoint of suppressing a decrease in the glass transition temperature (Tg) of the polymer.
In the formula (1), R ₃ represents a linear, branched or alicyclic hydrocarbon group having 1 to 12 carbon atoms. Examples of the hydrocarbon group include a straight chain hydrocarbon such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group, an isobutyl group, a t-butyl group, Branched hydrocarbon such as isopropyl group, cyclopentyl group, neopentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1,2-dimethylpropyl group, cyclohexyl group, isobornyl group, norbornanyl group, adamantyl group, Examples thereof include alicyclic hydrocarbon groups such as 1-adamantylmethyl group, 2-adamantylmethyl group, 1-adamantylethyl group and 2-adamantylethyl group. Among these, R ₃ is preferably an alicyclic hydrocarbon group in terms of suppressing a decrease in the glass transition temperature (Tg) of the polymer.

  These monomers (A) can be synthesized by a reaction between a vinyl ether compound represented by the following general formula (2) and (meth) acrylic acid. This reaction can be carried out without a catalyst and without a solvent, but when the vinyl ether compound is solid and the solubility in (meth) acrylic acid is insufficient, a solvent can be appropriately used.

  The proportion of the monomer (A) is preferably 20 mol% or more, and more preferably 25 mol% or more, in the total charge (100 mol%) of all monomers, from the viewpoint of sensitivity and resolution. Moreover, 60 mol% or less is preferable from the point of the adhesiveness to a board | substrate etc., 55 mol% or less is more preferable, and 50 mol% or less is further more preferable.

<Monomer (B)>
The monomer (B) is a monomer having a lactone ring. A (meth) acrylic acid ester having a lactone ring is preferred.
The lactone ring means a ring structure containing —C (═O) —O— in the ring. Examples of the lactone ring include a lactone ring having about 4 to 20 members. The lactone ring in the monomer (B) may be a single ring, and a lactone ring condensed with a carbocyclic ring derived from an alicyclic compound, a carbocyclic ring derived from an aromatic compound, or a heterocyclic ring. It may be a ring.
Specific examples of the monomer (B) include, but are not limited to, compounds represented by formulas (B-1) to (B-8), positional isomers or optical isomers of the compounds. In formulas (B-1) to (B-8), R in the formula represents a hydrogen atom or a methyl group.
A monomer (B) may be used individually by 1 type, and may be used in combination of 2 or more type.
The proportion of the monomer (B) is preferably 20 mol% or more, more preferably 35 mol% or more in the total amount of all monomers (100 mol%) from the viewpoint of adhesion to a substrate or the like. . Moreover, from the point of a sensitivity and resolution, 60 mol% or less is preferable, 55 mol% or less is more preferable, and 50 mol% or less is further more preferable.

<Monomer (C)>
A monomer (C) is a monomer which has polar groups other than a hydroxyl group. (Meth) acrylic acid esters having polar groups other than hydroxyl groups are preferred. The number of the polar groups in one molecule of the monomer (C) may be one, or two or more. For example, 1 to 3 is preferable.
The “polar group other than hydroxyl group” in the present invention means a cyano group, a linear or branched alkoxy group having 1 to 12 carbon atoms, an amino group, and a carboxy group (having a substituent by esterification reaction). Or at least one selected from the group consisting of: From the viewpoint of suppressing decomposition of the acetal group in the monomer (A), a cyano group or a linear or branched alkoxy group having 1 to 12 carbon atoms is preferable, and a cyano group or a methoxy group is particularly preferable.
Specific examples of the monomer (C) include, but are not limited to, compounds represented by the formulas (C-1) to (C-13), positional isomers or optical isomers of the compounds. In the formulas (C-1) to (C-13), R in the formula represents a hydrogen atom or a methyl group.
A monomer (C) may be used individually by 1 type, and may be used in combination of 2 or more type.
The proportion of the monomer (C) is preferably 1 to 30 mol% and more preferably 1 to 20 mol% in the total charge amount (100 mol%) of all monomers from the point of resist pattern rectangularity. .

<Other monomers>
Other monomers other than the above-mentioned monomers (A) to (C) may be further used as monomers used for producing the polymer of the present invention. Examples of the other monomer include an acid detachable monomer (D) other than the monomer (A) and a monomer (E) having an alicyclic skeleton.
In the present invention, a monomer having a hydroxyl group is not used.

<Monomer (D)>
The acid detachable monomer (D) (hereinafter referred to as monomer (D)) is a monomer having an acid labile group, preferably a (meth) acrylic acid ester having an acid labile group. It is. The “acid labile group” is a group having a bond that is cleaved by an acid, and part or all of the acid labile group is eliminated from the main chain of the polymer by cleavage of the bond.
When used as a resist composition, a resist polymer having an acid labile group is soluble in an alkali by an acid, and has the effect of enabling the formation of a resist pattern.

Examples of the monomer (D) include known acid-eliminating monomers.
Examples thereof include (meth) acrylic acid esters having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and a group capable of leaving by the action of an acid. The alicyclic hydrocarbon group may be directly bonded to an oxygen atom constituting an ester bond of (meth) acrylic acid ester, or may be bonded via a linking group such as an alkylene group.
The (meth) acrylic acid ester as the monomer (D) has an alicyclic hydrocarbon group having 5 to 20 carbon atoms and a bond with an oxygen atom constituting the ester bond of the (meth) acrylic acid ester. A (meth) acrylic acid ester having a tertiary carbon atom at the site; or an alicyclic hydrocarbon group having 5 to 20 carbon atoms, and a -COOR 'group (R' is (Meth) acrylic acid ester in which an optionally substituted tertiary hydrocarbon group, tetrahydrofuranyl group, tetrahydropyranyl group or oxepanyl group is bonded directly or via a linking group Is included.

Although it does not specifically limit as a specific example of a monomer (D), The compound represented by Formula (D-1)-(D-17) is mentioned. In the formulas (D-1) to (D-17), R in the formula represents a hydrogen atom or a methyl group.
A monomer (D) may be used individually by 1 type, and may be used in combination of 2 or more type.
The proportion of the monomer (D) is preferably 20 mol% or more in combination with the monomer (A) in the total charge (100 mol%) of all monomers from the viewpoint of sensitivity and resolution. Mole% or more is more preferable. Moreover, 60 mol% or less is preferable from the point of the adhesiveness to a board | substrate etc., 55 mol% or less is more preferable, and 50 mol% or less is further more preferable.

<Monomer (E)>
The alicyclic skeleton in the monomer (E) having an alicyclic skeleton (hereinafter referred to as monomer (E)) means a carbocyclic ring derived from an alicyclic compound. The alicyclic skeleton preferably has 5 to 20 carbon atoms. The monomer (E) is preferably a (meth) acrylic acid ester having an alicyclic skeleton.
The monomer contained in any of the monomers (A) to (D) is not included in the monomer (E).
Although it does not specifically limit as a specific example of a monomer (E), The compound represented by Formula (E-1)-(E-9) is mentioned. In the formulas (E-1) to (E-9), R in the formula represents a hydrogen atom or a methyl group.
A monomer (E) may be used individually by 1 type, and may be used in combination of 2 or more type.
By using the monomer (E), the dry etching resistance of the polymer can be improved. The proportion of the monomer (E) is preferably from 0 to 30 mol%, more preferably from 0 to 20 mol%, in the total charged amount (100 mol%) of all monomers. If it exceeds 30 mol%, adhesion and developer solubility may be reduced.

<Polymerization method>
[Polymerization process]
First, at least monomers (A) to (C) are copolymerized to produce a polymer. Along with the monomers (A) to (C), other monomers, preferably the monomer (D) and / or the monomer (E) may be copolymerized. Copolymerization is performed using a polymerization initiator.
The polymerization method is not particularly limited, and a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method can be used.
As the polymerization initiator, those that generate radicals efficiently by heat are preferable. For example, an azo compound (2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] etc.
), Organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc.).

In the polymerization step, the polymerization reaction is preferably performed in the presence of an amine in order to suppress the decomposition of the acetal skeleton of the monomer (A).
The amine to be used is not particularly limited as long as it has a boiling point higher than the polymerization temperature during polymerization, but triethylamine and pyridine are preferable because they are easily available and can be easily removed when the polymer is dried under reduced pressure. .
The added amount of amine is preferably 0.016 parts by mass or more based on 100 parts by mass of the total charge of monomers. Although there is no particular problem even if the amount of amine used is large, it is preferably 10 parts by mass or less from the economical viewpoint.

  The mass average molecular weight of the polymer is not particularly limited, but when the polymer is used as a component for forming a film such as a resist film, 1,000 to 100,000 is preferable, and 2,000 to 50,000 is more preferable. 3,000 to 30,000 are particularly preferred. If the mass average molecular weight is less than 1,000, the liquid containing the polymer may not be formed well when applied and dried on the substrate. If the weight average molecular weight is greater than 100,000, it may be applied with a uniform film thickness. May become difficult, and when used as a constituent component of a resist, the resist characteristics may be deteriorated.

The polymerization method is preferably a solution polymerization method from the viewpoint that the precipitation step described later is easy and that the molecular weight of the polymer can be relatively low.
In the solution polymerization method, the monomer and the polymerization initiator may be supplied to the polymerization vessel either continuously or dropwise. The drop polymerization method is preferred from the viewpoint that a polymer having good reproducibility can be easily obtained with small variations in average molecular weight, molecular weight distribution, etc. due to differences in production lots.

Hereinafter, the dropping polymerization method will be described.
In the dropping polymerization method, the inside of the polymerization vessel is heated to a predetermined polymerization temperature, and then the monomer and the polymerization initiator are dropped into the polymerization vessel independently or in any combination.
The monomer may be dropped only with the monomer, or may be dropped as a monomer solution in which the monomer is dissolved in a solvent (hereinafter also referred to as “dropping solvent”).
A solvent (hereinafter also referred to as “charged solvent”) may be charged into the polymerization vessel in advance, or the charged solvent may not be charged into the polymerization vessel in advance. When the charged solvent is not charged in the polymerization vessel in advance, the monomer or the polymerization initiator is dropped into the polymerization vessel in the absence of the charged solvent.

The polymerization initiator may be dissolved directly in the monomer, may be dissolved in the monomer solution, or may be dissolved only in the dropping solvent.
The monomer and the polymerization initiator may be dropped into the polymerization vessel after mixing in the same storage tank, or may be dropped from the independent storage tank into the polymerization container. They may be mixed immediately before the supply and dropped into the polymerization vessel.
One of the monomer and the polymerization initiator may be dropped first, and then the other may be dropped with a delay, or both may be dropped at the same timing.
The dropping rate may be constant until the end of dropping, or may be changed in multiple stages according to the consumption rate of the monomer or the polymerization initiator.
The dripping may be performed continuously or intermittently.

The polymerization temperature is preferably 50 to 150 ° C.
The solvent (dropping solvent or charging solvent) is not particularly limited as long as it dissolves the monomer used for the polymerization and the polymer to be produced, and is preferably a solvent that does not easily decompose the acetal skeleton of the monomer (A). For example, the following solvents are mentioned.
Ethers: chain ethers (diethyl ether, propylene glycol monomethyl ether, etc.), cyclic ethers (tetrahydrofuran (THF), 1,4-dioxane, etc.) and the like.
Esters: methyl acetate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”), γ-butyrolactone (hereinafter referred to as γ-BL), and the like.
Ketones: acetone, methyl ethyl ketone, methyl isobutyl ketone and the like.
Amides: N, N-dimethylacetamide, N, N-dimethylformamide and the like.
Sulfoxides: dimethyl sulfoxide and the like.
Aromatic hydrocarbons: benzene, toluene, xylene and the like.
Aliphatic hydrocarbon: hexane and the like.
Alicyclic hydrocarbons: cyclohexane and the like.
A solvent may be used individually by 1 type and may use 2 or more types together.

As an aspect of the dropping polymerization method, it is preferable to use the following partial dropping method in terms of suppressing variations in monomer composition in the polymer to be formed and variations in the chain structure of monomer units.
First, the reactor is charged with the first solution containing the monomer in the first composition, the reactor is heated to a predetermined polymerization temperature, and then the monomer is contained in the reactor. One or more dropping solutions are dropped.
If a monomer having the same monomer composition as the dropping solution is dropped uniformly over a certain period of time without previously charging the monomer into the reactor, the monomer having a slow monomer consumption rate in the copolymerization reaction is In the initial stage of polymerization, it is incorporated into the copolymer at a proportion smaller than the desired composition ratio, resulting in variations in monomer composition and chain structure.
Therefore, in the first composition of the first solution charged in the reactor in advance, the composition ratio (content ratio) of the monomer having a slow monomer consumption rate is set to be the same for all the solutions used for the polymerization reaction. It is larger than the composition ratio of the monomer in the total amount.

Specifically, two or more types of monomers α1 to αn (n is an integer of 2 or more) are polymerized in the reactor while dropping a monomer and a polymerization initiator in the reactor. A polymerization method for obtaining a polymer (P) comprising units α′1 to α′n (where α′1 to α′n represents structural units derived from monomers α1 to αn, respectively), A polymerization method having the following steps (I) and (II) is preferred.
(I) Before the polymerization initiator is dropped into the reactor or simultaneously with the start of dropping the polymerization initiator, the monomers α1 to αn are added to the reactor according to the reactivity ratio of each monomer. Supplying a first solution containing the first composition in a proportion to be polymerized in a steady state from the initial stage of polymerization;
(II) The target composition (unit: mol%) representing the content ratio of the structural units α′1 to α′n in the polymer (P) to be obtained is α′1: α′2:. When the second solution containing the monomers α1 to αn in the same composition as the target composition after starting the supply of the first solution into the reactor or simultaneously with the start of the supply of the first solution. Supplying the solution.

In this method, when the content ratio of the monomer present in the reactor is the first composition, the first composition is immediately after the second solution is dropped into the reactor. The composition ratio is designed so that the content ratio of the constituent units of the polymer molecules produced in the above is the same as the target composition. In this case, since the content ratio of the structural unit in the polymer molecule produced immediately after the dropping is the same as the content ratio (target composition) of the monomer in the dropped second solution, The content ratio of the remaining monomer is always constant (first composition). Therefore, when the second solution is continuously dropped into the reactor, a steady state in which polymer molecules having a target composition are always generated can be obtained.
Therefore, in the first composition, the composition ratio (content ratio) of the monomer having a slow monomer consumption rate is such that the steady state is obtained, and the total amount of all the solutions used in the polymerization reaction is the same. The composition ratio is larger than the monomer composition ratio.

Furthermore, a monomer having a slow monomer consumption rate in the copolymerization reaction is incorporated into the copolymer at a rate higher than the desired composition ratio in the late stage of polymerization, resulting in variations in the monomer composition and chain structure.
Therefore, the present method contains a monomer to be supplied into the reactor after heating the reactor to a predetermined polymerization temperature in that it is easier to produce a copolymer with less variation in copolymer composition. It is preferable to prepare two or more dropping solutions, and drop one of them in the late polymerization stage. For example, in the case of the method using the first solution and the second solution (drip solution), the addition of the second solution to the drop solution (third solution) having a composition different from that of these solutions is completed. Drop later.

  In the dropping solution dropped in the late stage of the polymerization, the composition ratio of the monomer having a high monomer consumption rate may be larger than the composition ratio of the monomer in the total amount of all the solutions used in the polymerization reaction. preferable. Moreover, it is preferable that the dropping solution dropped in the latter stage of the polymerization does not contain a monomer having the slowest monomer consumption rate. Further, the total amount of monomers contained in the dropping solution dropped in the late stage of the polymerization is 0.1 to 10% by mass, preferably 0.1 to 7.5% by mass, more preferably the total monomer supply amount. It is preferable that it is 0.1-5 mass%.

The polymerization initiator may be contained in a dropping solution containing a monomer, or may be dropped into the reactor separately from the monomer.
The dropping speed may be constant until the dropping is completed, or may be changed in multiple stages according to the monomer consumption. The dripping may be performed continuously or intermittently.
Examples of the solvent for the first solution and the dropping solution include various solvents as described above. A solvent may be used individually by 1 type and may use 2 or more types together.
Examples of the polymerization initiator include various compounds as described above.

[Precipitation process]
In the present invention, the purification is performed by mixing the polymer solution containing the polymer produced in the polymerization step with a poor solvent and precipitating the polymer in the polymer solution.
It was obtained when the polymer produced in the polymerization process was obtained in a solution (polymer solution) dissolved in a solvent, such as when a monomer copolymerization reaction was performed by a solution polymerization method. The polymer solution can be used as it is or diluted for the precipitation step.
In addition, when the copolymerization reaction of monomers is performed by a bulk polymerization method, a solution obtained by dissolving the obtained polymer in an appropriate solvent can be used as a polymer solution in the precipitation step.

In the present invention, alcohol is used as a poor solvent for precipitating the polymer. As the alcohol, known alcohols can be used as the organic solvent. Specific examples include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and t-butanol. Among these, low boiling point methanol, ethanol or isopropanol is preferable, and methanol is particularly preferable from the viewpoint of efficiency in drying the precipitated polymer to remove the solvent.
Normally, alcohol contains moisture, and anhydrous alcohol also contains about 0.5% or less moisture. In the present invention, the alcohol used as the poor solvent in the precipitation step may contain moisture as long as the effects of the present invention are not impaired. Specifically, the water content of the alcohol may be less than 10% by mass, preferably 5% by mass or less, and more preferably 2% by mass or less.
That is, the poor solvent used in the precipitation step may contain water of less than 10% by mass, preferably 5% by mass or less, more preferably 2% by mass or less, and the rest is alcohol.

The method of mixing the polymer solution and the poor solvent may be mixed together, but the method of dropping the polymer solution into the poor solvent is the monomer and solvent remaining in the precipitated polymer Is preferable in that it can be reduced. In this case, the dropping speed of the polymer solution is not particularly limited, and can be set as appropriate. It is preferable to slowly drop the polymer solution.
Although the liquid temperature after mixing a polymer solution and a poor solvent is not specifically limited, Preferably it is performed at 0-50 degreeC.
The amount of the poor solvent to be mixed with the polymer solution is not particularly limited, but is preferably about 3 to 20 times by volume with respect to the polymer solution.

  According to the production method of the present invention, a polymer obtained by copolymerizing at least a monomer having an acetal skeleton, a monomer having a lactone ring, and a monomer having a polar group other than a hydroxyl group is obtained. The polymer can be precipitated from the polymer solution containing it while suppressing the decomposition of the acetal skeleton. Therefore, a polymer in which the generation of impurities due to the decomposition of the acetal skeleton is suppressed can be obtained.

[Post-processing process]
The polymer precipitate thus obtained is filtered off, washed as necessary, and dried to obtain a polymer powder. Alternatively, after filtering and washing as necessary, the powder can be used in the form of a wet powder without being dried and dissolved in a suitable solvent.
The solvent used for washing is preferably a poor solvent that does not cause decomposition of the acetal skeleton, and is preferably the same poor solvent that can be used in the precipitation step.
The polymer obtained by the production method of the present invention is suitable as a polymer for semiconductor lithography, and particularly suitable as a polymer for chemically amplified resist.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
The reaction reagents and monomers used in the following examples were used as they were without purifying commercial products unless otherwise specified.
The structures of monomers (A-1), (B-1), (C-1), and (C-14) used in the following examples are shown below.

Various physical properties of the polymer were measured by the following methods.
[Measurement of mass average molecular weight of polymer]
About 20 mg of polymer is dissolved in 5 mL of THF and filtered through a 0.5 μm membrane filter to prepare a sample solution. This sample solution is measured using gel permeation chromatography (GPC) manufactured by Tosoh Corporation. did. In this measurement, a separation column was manufactured by Showa Denko Co., Ltd., and three Shodex GPC K-805L (trade name) connected in series, the developing solvent was THF, the flow rate was 1.0 mL / min, and the detector was a differential refractometer. The mass average molecular weight was measured using polystyrene as a standard polymer at a measurement temperature of 40 ° C. and an injection amount of 0.1 mL.

[Determination of acetal decomposition ratio]
By measuring ¹ H-NMR spectrum, the decomposition ratio of acetal is determined from the ratio of carboxy group (11.9-12.6 ppm) generated by decomposition of acetal and 1H (5.7-5.9 ppm) derived from acetal. did. This measurement was performed by using a GSX-400 FT-NMR (trade name) manufactured by JEOL Ltd. and putting a monomer deuterated dimethyl sulfoxide solution having a concentration of about 5% by mass into a test tube having a diameter of 5 mmφ. The measurement was performed at a measurement temperature of 40 ° C., a measurement frequency of 400 MHz, and a single pulse mode with 64 integrations.

[Example 1]
(Polymerization process)
A flask equipped with a dropping funnel, a condenser, a thermometer, a nitrogen gas inlet, and a stirrer was charged with PGMEA (9.5 g) as a polymerization solvent, and the atmosphere in the flask was replaced with nitrogen. Heated to ° C.
Separately from this, monomer (A-1) (4.24 g, 20 mmol), 50 mass% PGMEA solution of monomer (B-1) (9.44 g, 20 mmol), monomer (C-1 ) (2.05 g, 10 mmol), triethylamine (0.404 g, 0.40 mmol), and dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name), 1.136 g) , 5.0 mmol) was dissolved in PGMEA (12.4 g), and 4-methoxyphenol (0.41 mg, 200 ppm) was further added as a polymerization inhibitor to prepare a monomer solution.
This monomer solution was put into a dropping funnel and dropped into the polymerization solvent in the flask over 4 hours. After completion of the dropping, the polymer was kept for 3 hours while maintaining the internal temperature at 80 ° C. to obtain a polymer solution.

(Precipitation process)
As a poor solvent to be mixed with the polymer solution, 260 mL of anhydrous methanol (methanol concentration of 99.8% by mass or more) was prepared. While maintaining this at 40 ° C. and stirring at a rate of 200 rpm, the polymer solution obtained above was added dropwise and held for 30 minutes to obtain a white precipitate.
(Post-processing process)
In order to remove the monomer remaining in the precipitate, the resulting precipitate was filtered off, suspended in anhydrous methanol (260 mL) heated to 40 ° C., and stirred for 30 minutes at a speed of 200 rpm. Washed. The precipitate was further filtered and dried at 60 ° C. for 36 hours to obtain a polymer. The obtained polymer had a weight average molecular weight (Mw) of 8900 and Mw / Mn = 1.5.
As a result of measuring ¹ H-NMR, no decomposition of acetal was observed.

[Comparative Example 1]
In Example 1, it superposed | polymerized by the method similar to Example 1 except having replaced with the monomer (C-1) and having used the monomer (C-14) which has a hydroxyl group (2.36g, 10 mmol). Steps and precipitation steps were performed. In the precipitation step, when the polymer solution was dropped, the polymer aggregated in methanol and became sticky, and the polymer could not be purified.

[Comparative Example 2]
In Example 1, instead of the monomer (C-1), a monomer (C-14) having a hydroxyl group (2.36 g, 10 mmol) was used. As a poor solvent, a mixed solvent of methanol (182 mL) and water (78 mL) (water content 30%) was used instead of anhydrous methanol. Other than that, the polymerization step and the precipitation step were performed in the same manner as in Example 1.
The obtained polymer had a mass average molecular weight (Mw) of 9900 and Mw / Mn = 1.8.
As a result of measuring ¹ H-NMR, acetal decomposition was observed at a decomposition ratio of 18.1%.

Claims (1)

At least the monomer (A) represented by the following general formula (1), the monomer (B) having a lactone ring, and the monomer (C) having a polar group other than a hydroxyl group are copolymerized. A polymerization process;
The polymer solution containing the polymer obtained in the polymerization step is mixed with a poor solvent to have a precipitation step of precipitating the polymer in the polymer solution,
The method for producing a polymer, wherein the poor solvent is an alcohol having a water content of less than 10% by mass.

(In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom or a linear or branched hydrocarbon group having 1 to 6 carbon atoms, and R ₃ has 1 to 12 carbon atoms. Represents a linear, branched, or alicyclic hydrocarbon group.)