JP5707699B2 - Method for producing polymer, method for producing resist composition, and method for producing substrate - Google Patents

Description

  The present invention provides a method for producing a polymer, a polymer for lithography obtained by the production method, a resist composition using the polymer for lithography, and a substrate on which a pattern is formed using the resist composition. Regarding the method.

In the manufacturing process of semiconductor elements, liquid crystal elements, etc., in recent years, pattern formation by lithography has been rapidly miniaturized. As a technique for miniaturization, there is a reduction in wavelength of irradiation light.
Recently, KrF excimer laser (wavelength: 248 nm) lithography technology has been introduced, and ArF excimer laser (wavelength: 193 nm) lithography technology and EUV (wavelength: 13.5 nm) lithography technology for further shortening the wavelength have been studied. .
Further, for example, as a resist composition that can suitably cope with a shorter wavelength of irradiation light and a finer pattern, a polymer in which an acid-eliminable group is eliminated by the action of an acid and becomes alkali-soluble, and a photoacid generator A so-called chemically amplified resist composition containing the above has been proposed, and its development and improvement are underway.

As a chemically amplified resist polymer used in ArF excimer laser lithography, an acrylic polymer that is transparent to light having a wavelength of 193 nm has attracted attention.
For example, in the following Patent Document 1, (A) (meth) acrylic acid ester in which an alicyclic hydrocarbon group having a lactone ring is ester-bonded and (B) an acid can be eliminated as a monomer. (Meth) acrylic acid ester having an ester bond, and (C) a (meth) acrylic acid ester having a polar substituent and a hydrocarbon group or oxygen atom-containing heterocyclic group bonded to each other. Copolymers for lithography are described.

With the miniaturization of resist patterns, the demands on the quality of lithography polymers are becoming stricter. For example, a very small amount of high molecular weight component (high polymer) produced in the polymerization process causes a decrease in the solubility of the lithography polymer in the resist solvent and the solubility in the alkali developer, and as a result, the resist composition Sensitivity decreases.
In the following Patent Document 2, as a method of suppressing the formation of such a high polymer, a solution containing a polymerizable monomer and a solution containing a polymerization initiator are held in independent storage tanks, and the polymerization initiator is polymerized. A method has been proposed in which the monomer is supplied into the polymerization system before the monomer.

JP 2002-145955 A JP 2004-269855 A

However, the method described in Patent Document 2 may not sufficiently improve the solubility of the polymer for lithography or the sensitivity of the resist composition.
The present invention has been made in view of the above circumstances, and can improve the dispersion of the molecular weight in the copolymer, improve the solubility in a solvent and the sensitivity when used in a resist composition, An object of the present invention is to provide a lithographic polymer obtained by the production method, a resist composition using the lithographic polymer, and a method for producing a substrate on which a pattern is formed using the resist composition.

In order to solve the above-mentioned problem, the first aspect of the present invention is the addition of two or more monomers α _{1 to} α _{n in the} reactor while dropping the monomer and the polymerization initiator in the reactor. (Wherein _n represents an integer of 2 or more) is polymerized to form structural units α ′ _{1 to} α ′ _n (where α ′ _{1 to} α ′ _n are derived from monomers α _{1 to} α _n , respectively). A radical polymerization initiator comprising a polymerization step of obtaining a polymer (P) comprising a structural unit), wherein the monomer is a (meth) acrylic acid ester , and the polymerization initiator is an azo compound. A monomer solution containing the monomers α _{1 to} α _n in the reactor before the polymerization initiator is dropped into the reactor or simultaneously with the start of dropping of the polymerization initiator. When the reference time starts from the start of dropping the polymerization initiator to the end of the dropping of the monomer solution, the reference time Is a value obtained by dividing the total supply amount of the polymerization initiator by the reference time as an average supply rate Vj, from 0% to j% (j is 5 to 20) of the reference time The period is a high-speed supply period of the polymerization initiator in which the polymerization initiator is dropped at a speed higher than the average supply speed Vj, and a value obtained by dividing the total supply amount of the monomer by the reference time is the average supply speed Vk. In the period from 0% to k% (k is 0 to 20) of the reference time, the monomer α _{1 to} α _n is supplied at a higher speed than the average supply speed Vk. The weight average molecular weight value of the polymer in the reactor at 30 minutes, 1 hour, and 2 hours after the start of dropping of the polymerization initiator is the polymer (P ) Of the polymerization initiator so as to be 80 to 120% of the weight average molecular weight of 30 to 90% by mass of the total supply amount of the polymerization initiator is supplied into the reactor during the fast supply period, and the total supply amount of the monomer is supplied during the high-speed supply period of the monomer. It is a manufacturing method of the polymer which supplies 2-50 mass% in the said reactor.

According to a second aspect of the present invention, in the first aspect, after the completion of the high-speed supply period of the polymerization initiator, the polymerization initiator is dropped at a constant rate, and after the completion of the high-speed supply period of the monomer. Is a method for producing a polymer in which the monomer is dropped at a constant rate.
A third aspect of the present invention is a method for producing a polymer according to the first or second aspect, wherein the polymer (P) is a polymer for lithography.

According to a fourth aspect of the present invention, there is provided a step of producing a lithographic polymer by the production method of the present invention, and the obtained lithographic polymer, a resist solvent, and a compound capable of generating an acid upon irradiation with actinic rays or radiation. It is a manufacturing method of the resist composition which has the process to mix .
A fifth aspect of the present invention includes a step of producing a resist composition by the production method of the present invention, a step of coating the obtained resist composition on a work surface of a substrate to form a resist film, It is a method for manufacturing a substrate on which a pattern is formed, which includes a step of exposing a resist film and a step of developing the exposed resist film using a developer.

According to the method for producing a polymer of the present invention, it is possible to obtain a polymer that can improve variation in molecular weight, improve solubility in a solvent, and sensitivity when used in a resist composition.
The lithographic polymer of the present invention has improved molecular weight variation, good solubility in a solvent, and high sensitivity when used in a resist composition.
The resist composition of the present invention is a chemically amplified type, has excellent solubility in a resist solvent, and is excellent in sensitivity.
According to the substrate manufacturing method of the present invention, a highly accurate fine resist pattern can be stably formed.

6 is a graph showing the results of Reference Example 1. 6 is a graph showing the results of Reference Example 1. 3 is a graph showing the results of Example 1. 3 is a graph showing the results of Example 1. 10 is a graph showing the results of Example 2. 10 is a graph showing the results of Example 2. 10 is a graph showing the results of Reference Example 2. 10 is a graph showing the results of Reference Example 2. 10 is a graph showing the results of Example 3. 10 is a graph showing the results of Example 3.

In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acryloyloxy” means acryloyloxy or methacryloyloxy.
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer in the present invention are values obtained by gel permeation chromatography in terms of polystyrene.

<Polymer (P)>
The polymer (P) of the present invention is a structural unit α ′ _{1 to} α ′ _n (where α ′ _{1 to} α ′ _n represent structural units derived from the monomers α _{1 to} α _n , respectively, where n is 2 or more. Represents an integer of. The upper limit of n is preferably 6 or less in that the effect of the present invention can be easily obtained. In particular, when the polymer (P) is a resist polymer, 5 or less is more preferable, and 4 or less is more preferable.
For example, when n = 3, the polymer (P) is a ternary polymer P (α ′ ₁ / α ′ ₂ / α ′ ₃ ) composed of structural units α ′ ₁ , α ′ ₂ and α ′ _3. And when n = 4, the quaternary polymer P (α ′ ₁ / α ′ ₂ / α ′ ₃ / α ′ consisting of structural units α ′ ₁ , α ′ ₂ , α ′ ₃ , α ′ _{4) 4} ).

The application of the polymer (P) is not particularly limited. For example, a polymer for lithography used in the lithography process is preferable. As a polymer for lithography, a resist polymer used for forming a resist film, an antireflection film (TARC) formed on the upper layer of the resist film, or an antireflection film (BARC) formed on the lower layer of the resist film. Examples thereof include a polymer for antireflection film used for forming, a polymer for gap fill film used for forming a gap fill film, and a polymer for top coat film used for forming a top coat film.
The weight average molecular weight (Mw) of the polymer for lithography is preferably from 1,000 to 200,000, more preferably from 2,000 to 40,000. The molecular weight distribution (Mw / Mn) is preferably 1.0 to 10.0, and more preferably 1.1 to 4.0.

The structural unit of the polymer (P) is not particularly limited, and is appropriately selected according to the use and required characteristics.
The resist polymer preferably has a structural unit having an acid-eliminable group and a structural unit having a polar group. In addition, the resist polymer may have a known structural unit if necessary.
The weight average molecular weight (Mw) of the resist polymer is preferably 1,000 to 100,000, and more preferably 3,000 to 30,000. The molecular weight distribution (Mw / Mn) is preferably from 1.0 to 3.0, more preferably from 1.1 to 2.5.

The polymer for an antireflection film has, for example, a structural unit having a light absorbing group and an amino group, an amide group, a hydroxyl group, an epoxy that can be cured by reacting with a curing agent in order to avoid mixing with a resist film. It is preferable to include a structural unit having a reactive functional group such as a group.
The light-absorbing group is a group having high absorption performance with respect to light in a wavelength region where the photosensitive component in the resist composition is sensitive. Specific examples include an anthracene ring, naphthalene ring, benzene ring, quinoline ring. , A group having a ring structure (optionally substituted) such as a quinoxaline ring and a thiazole ring. In particular, when KrF laser light is used as irradiation light, an anthracene ring or an anthracene ring having an arbitrary substituent is preferable, and when ArF laser light is used, a benzene ring or a benzene having an arbitrary substituent A ring is preferred.
Examples of the optional substituent include a phenolic hydroxyl group, an alcoholic hydroxyl group, a carboxy group, a carbonyl group, an ester group, an amino group, and an amide group.
In particular, a polymer for an antireflection film having a protected or unprotected phenolic hydroxyl group as a light-absorbing group is preferable from the viewpoint of good developability and high resolution.
Examples of the structural unit / monomer having the light-absorbing group include benzyl (meth) acrylate and p-hydroxyphenyl (meth) acrylate.

The polymer for gap fill film has, for example, a reactive functional group that has an appropriate viscosity for flowing into a narrow gap and can be cured by reacting with a curing agent to avoid mixing with a resist film or an antireflection film. It is preferable to include a structural unit having
Specific examples include copolymers of hydroxystyrene and monomers such as styrene, alkyl (meth) acrylate, and hydroxyalkyl (meth) acrylate.
Examples of the polymer for the topcoat film used in immersion lithography include a copolymer containing a structural unit having a carboxyl group, a copolymer containing a structural unit having a fluorine-containing group substituted with a hydroxyl group, and the like.

<Constitutional unit / monomer>
The polymer (P) is obtained by polymerizing monomers α _{1 to} α _n corresponding to the structural units α ′ _{1 to} α ′ _n , respectively. The monomer is preferably a compound having a vinyl group, and is preferably a monomer that easily undergoes radical polymerization. In particular, (meth) acrylic acid ester is highly transparent to exposure light having a wavelength of 250 nm or less.
Hereinafter, when the polymer (P) is a resist polymer, a structural unit and a monomer corresponding to it will be described.

[Structural Unit / Monomer Having Acid Leaving Group]
The resist polymer preferably has an acid leaving group. The “acid leaving group” is a group having a bond that is cleaved by an acid, and a part or all of the acid leaving group is removed from the main chain of the polymer by cleavage of the bond.
In the resist composition, a polymer having a structural unit having an acid-eliminable group reacts with an acid component to become soluble in an alkaline solution, and has an effect of enabling resist pattern formation.
The proportion of the structural unit having an acid leaving group is preferably 20 mol% or more, more preferably 25 mol% or more, out of all the structural units (100 mol%) constituting the polymer 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.

The monomer having an acid leaving group may be any compound having an acid leaving group and a polymerizable multiple bond, and known ones can be used. The polymerizable multiple bond is a multiple bond that is cleaved during the polymerization reaction to form a copolymer chain, and an ethylenic double bond is preferable.
Specific examples of the monomer having an acid leaving group include (meth) acrylic acid esters having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and having an acid leaving group. It is done. 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 has an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and a tertiary carbon atom at the bonding site with the oxygen atom constituting the ester bond of the (meth) acrylic acid ester. A (meth) acrylic acid ester having an alicyclic group or an alicyclic hydrocarbon group having 6 to 20 carbon atoms and a -COOR group (R may have a substituent) on the alicyclic hydrocarbon group. (Meth) acrylic acid ester in which a tertiary hydrocarbon group, a tetrahydrofuranyl group, a tetrahydropyranyl group, or an oxepanyl group is bonded directly or via a linking group is included.

In particular, in the case of producing a resist composition that is applied to a pattern forming method that is exposed to light having a wavelength of 250 nm or less, as a preferred example of a monomer having an acid leaving group, for example, 2-methyl-2- Adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, 1- (1′-adamantyl) -1-methylethyl (meth) acrylate, 1-methylcyclohexyl (meth) acrylate, 1-ethylcyclohexyl ( Examples include meth) acrylate, 1-methylcyclopentyl (meth) acrylate, 1-ethylcyclopentyl (meth) acrylate, isopropyl adamantyl (meth) acrylate, 1-ethylcyclooctyl (meth) acrylate, and the like.
Among these, 1-ethylcyclohexyl methacrylate (m2 in Examples), 2-methyl-2-adamantyl methacrylate (m5 in Examples), 1-ethylcyclopentyl methacrylate, and isopropyl adamantyl methacrylate are more preferable.
As the monomer having an acid leaving group, one type may be used alone, or two or more types may be used in combination.

[Constitutional unit / monomer having a polar group]
The “polar group” is a group having a polar functional group or a polar atomic group. Specific examples include a hydroxy group, a cyano group, an alkoxy group, a carboxy group, an amino group, a carbonyl group, and a fluorine atom. A group containing a sulfur atom, a group containing a lactone skeleton, a group containing an acetal structure, a group containing an ether bond, and the like.
Among these, the resist polymer applied to the pattern forming method that is exposed to light having a wavelength of 250 nm or less preferably has a structural unit having a lactone skeleton as the structural unit having a polar group, It is preferable to have a structural unit having a functional group.

(Constitutional unit / monomer having a lactone skeleton)
Examples of the lactone skeleton include a lactone skeleton having about 4 to 20 members. The lactone skeleton may be a monocycle having only a lactone ring, or an aliphatic or aromatic carbocyclic or heterocyclic ring may be condensed with the lactone ring.
When the copolymer includes a structural unit having a lactone skeleton, the content thereof is preferably 20 mol% or more of all structural units (100 mol%) from the viewpoint of adhesion to a substrate and the like, and 35 mol%. The above is more preferable. 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.

  As a monomer having a lactone skeleton, a (meth) acrylic acid ester having a substituted or unsubstituted δ-valerolactone ring, a substituted or unsubstituted γ-butyrolactone ring is used because of its excellent adhesion to a substrate or the like. Preferably, at least one selected from the group consisting of monomers having it is preferred, and monomers having an unsubstituted γ-butyrolactone ring are particularly preferred.

Specific examples of the monomer having a lactone skeleton include β- (meth) acryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β- (meth) acryloyl. Oxy-γ-butyrolactone, β- (meth) acryloyloxy-β-methyl-γ-butyrolactone, α- (meth) acryloyloxy-γ-butyrolactone, 2- (1- (meth) acryloyloxy) ethyl-4-butanolide , (Meth) acrylic acid pantoyl lactone, 5- (meth) acryloyloxy-2,6-norbornanecarbolactone, 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decane-3 -One, 9-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one and the like. Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
Among these, α-methacryloyloxy-γ-butyrolactone (Example m1), α-acryloyloxy-γ-butyrolactone (Example m4), 5-methacryloyloxy-2,6-norbornanecarbolactone, 8-methacryloxy -4-Oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one is more preferred.
Monomers having a lactone skeleton may be used alone or in combination of two or more.

(Structural unit / monomer having a hydrophilic group)
The “hydrophilic group” in the present specification is at least one of —C (CF ₃ ) ₂ —OH, a hydroxy group, a cyano group, a methoxy group, a carboxy group, and an amino group.
Among these, it is preferable that the resist polymer applied to the pattern forming method exposed to light having a wavelength of 250 nm or less has a hydroxy group or a cyano group as a hydrophilic group.
The content of the structural unit having a hydrophilic group in the copolymer is preferably 5 to 30 mol%, more preferably 10 to 25 mol%, of the total structural units (100 mol%) from the viewpoint of resist pattern rectangularity. preferable.

  Examples of the monomer having a hydrophilic group include a (meth) acrylic acid ester having a terminal hydroxy group; a derivative having a substituent such as an alkyl group, a hydroxy group, or a carboxy group on the hydrophilic group of the monomer; Monomers having a cyclic hydrocarbon group (for example, cyclohexyl (meth) acrylate, 1-isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, (meth) acrylic acid) Dicyclopentyl, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, etc.) having a hydrophilic group such as a hydroxy group or a carboxy group as a substituent; Can be mentioned.

Specific examples of the monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxy- (meth) acrylate. -Propyl, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate, etc. Is mentioned. From the viewpoint of adhesion to a substrate or the like, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate and the like are preferable.
Among these, 3-hydroxyadamantyl methacrylate (m3 in Examples) and 2-cyanomethyl-2-adamantyl methacrylate (m6 in Examples) are more preferable.
The monomer which has a hydrophilic group may be used individually by 1 type, and may be used in combination of 2 or more type.

<Polymerization initiator>
The polymerization initiator is preferably one that decomposes by heat and efficiently generates radicals, and one having a 10-hour half-life temperature of not more than the polymerization temperature is preferably used. For example, when producing a polymer for lithography, a preferable polymerization temperature is 50 to 150 ° C., and a polymerization initiator having a 10-hour half-life temperature of 50 to 70 ° C. is preferably used. In order for the polymerization initiator to be efficiently decomposed, the difference between the 10-hour half-life temperature of the polymerization initiator and the polymerization temperature is preferably 10 ° C. or more.
Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2 , 2′-azobis [2- (2-imidazolin-2-yl) propane] and other azo compounds, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert- And organic peroxides such as butylcyclohexyl) peroxydicarbonate. An azo compound is more preferable.
These are available from commercial products. For example, dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, V601 (trade name), 10 hour half-life temperature 66 ° C.), 2,2′-azobis (2,4-dimethylvaleronitrile) ) (Manufactured by Wako Pure Chemical Industries, Ltd., V65 (trade name), 10 hour half-life temperature 51 ° C.) and the like can be suitably used.

<Solvent>
In the method for producing the polymer of the present invention, a polymerization solvent may be used. Examples of the polymerization solvent include the following.
Ethers: chain ethers (eg, diethyl ether, propylene glycol monomethyl ether), cyclic ethers (eg, tetrahydrofuran (hereinafter sometimes referred to as “THF”), 1,4-dioxane, etc.).
Esters: methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate (hereinafter sometimes referred to as “PGMEA”), γ-butyrolactone, 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 polymerization solvent may be used individually by 1 type, and may use 2 or more types together.
Although the usage-amount of a polymerization solvent is not specifically limited, For example, the quantity from which the solid content concentration of the liquid (polymerization reaction solution) in the reactor at the time of completion | finish of polymerization reaction will be about 20-40 mass% is preferable.

<Method for producing polymer>
In the method for producing a polymer of the present invention, two or more types of monomers α _{1 to} α _n are polymerized in the reactor while dropping the monomer and the polymerization initiator in the reactor, and the structural unit is obtained. a polymerization step for obtaining a polymer (P) composed of α ′ _{1 to} α ′ _n .
The polymerization step is performed by a radical polymerization method. In the present invention, a dropping polymerization method is used in which polymerization is performed in the reactor while the monomer and the polymerization initiator are dropped in the reactor.

The total amount of monomers used for the polymerization (total monomer supply amount) is set according to the amount of the polymer (P) to be obtained.
The amount (total supply amount) of the polymerization initiator is set according to the type of the polymerization initiator and according to the target value of the weight average molecular weight of the polymer (P) to be obtained.
For example, when the polymer (P) in the present invention is a lithography polymer, the amount of polymerization initiator used (100 mol% of the total amount of monomers supplied to the reactor (total supply amount) ( The total supply amount) is preferably in the range of 1 to 25 mol%, more preferably in the range of 1.5 to 20 mol%.

In the present invention, as described later, the monomer supply rate into the reactor changes in two or more stages, and the polymerization initiator supply rate also changes in two or more stages. That is, a high-speed monomer supply period and a high-polymerization initiator supply period are provided at the beginning of the polymerization step.
The high-speed monomer supply period may be realized, for example, by preparing a single monomer solution containing the monomers α _{1 to} α _n and changing the supply rate of the monomer solution. Alternatively, it may be realized by using two or more types of monomer solutions containing the monomers α _{1 to} α _n and having different supply periods.
A method using two or more monomer solutions is preferable in that the conditions during production are fixed and the reproducibility of the polymerization reaction is easily obtained.

When using 2 or more types of monomer solutions, the content ratio (composition) of the monomers contained in each solution may be the same or different. In either case, the effect of reducing the variation in the molecular weight of the polymer (P) can be obtained.
In particular, as a liquid containing the monomer, a _first solution containing the monomers α _{1 to} α _n in a first composition described later and a second composition including the monomers α _{1 to} α _n described later. When the second solution contained in is used, it is preferable because the variation in the molecular weight of the polymer (P) can be reduced and the variation in the content ratio of the structural units in the polymer (P) can be reduced. The first solution and the second solution preferably contain a solvent.

[Second solution]
The monomer content ratio (second composition) in the second solution is the same as the target composition representing the content ratio of the structural units α ′ _{1 to} α ′ _n in the polymer (P) to be obtained.
For example, the polymer (P) is a ternary polymer obtained by copolymerizing the monomers x, y, and z, and the target composition (mol%, the same applies hereinafter) is x ′: y ′: When z ′, the second composition (mol%, the same shall apply hereinafter) x: y: z is the same as x ′: y ′: z ′.
The second solution is fed dropwise to the reactor.

[First solution]
The content ratio (first composition) of the monomer in the first solution is a composition obtained in advance by taking into account the target composition in the polymer (P) and the reactivity of each monomer used in the polymerization. It is.
Specifically, the first composition is formed immediately after the dropping, when the content ratio of the monomer present in the reactor is the first composition, and 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 to be obtained is the same as the target composition. In this case, since the content ratio of the constituent units of the polymer molecules produced immediately after the dropping is the same as the monomer content ratio (target composition) of the dropped second solution, the inside of the reactor immediately after the dropping. 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.
The existence of the first composition capable of obtaining such a steady state has not been known prior to the present invention, and is a knowledge obtained for the first time by the present inventors. A specific example of the design method of the first composition will be described later.
The first solution may be charged in the reactor in advance, gradually supplied to the reactor by dropping or the like, or a combination thereof.

[Polymerization initiator]
The polymerization initiator is supplied dropwise to the reactor. The polymerization initiator may be contained in the monomer solution to be dropped, or a solution containing a polymerization initiator (polymerization initiator solution) may be dropped separately from the monomer solution. These may be combined.
When using the first solution and the second solution, the second solution may contain a polymerization initiator. When the first solution is dropped, a polymerization initiator may be contained in the first solution.

[Polymerization process]
In the polymerization step, it is necessary that the monomers α _{1 to} α _n exist in the reactor when the polymerization initiator is dropped into the reactor. Therefore, before the polymerization initiator is dropped into the reactor or simultaneously with the start of dropping of the polymerization initiator, the supply of the monomer solution into the reactor is started.
The end of dropping of the polymerization initiator and the end of supply of the monomer solution are preferably simultaneous, but may be slightly changed as long as the effects of the present invention are not hindered.

Further, when the reference time is from the start of dropping of the polymerization initiator to the end of dropping of the monomer solution, the value obtained by dividing the total supply amount of the monomer by the reference time is defined as the average supply rate Vk. A period from 0% to k% (k is 0 to 20) is a high-speed supply period of the monomer that supplies the monomers α _{1 to} α _n at a speed higher than the average supply speed Vk.
In the present invention, the reference time is 2 hours or more. The upper limit of the reference time is not particularly limited, but is preferably 20 hours or less and more preferably 15 hours or less from the viewpoint of productivity.
The high-speed monomer supply period may be zero percent of the reference time. That is, before starting the dropping of the polymerization initiator, the entire amount of the monomer supplied within the high-speed supply period may be supplied into the reactor.
The end point of the high-speed monomer supply period is the point when k% of the reference time has elapsed. k is 20 or less, preferably 15 or less, and more preferably 10 or less.
The monomer supply rate during the high-speed monomer supply period may be higher than the average supply rate, and the supply rate may be changed in the middle.
The monomer supply rate after the end of the high-speed monomer supply period may be lower than the average supply rate, and the supply rate may be changed in the middle, but the uniform polymer is stabilized. Therefore, it is preferable to drop at a constant rate.

When the first solution and the second solution are used, it is necessary that the first solution be present in the reactor when the polymerization initiator is dropped into the reactor. Therefore, before the polymerization initiator is dropped into the reactor or simultaneously with the start of dropping of the polymerization initiator, the supply of the first solution into the reactor is started.
In addition, when the second solution is dropped into the reactor, the first solution needs to be present in the reactor. Therefore, after starting the supply of the first solution into the reactor or simultaneously with the start of the supply of the first solution, the dropping of the second solution into the reactor is started.
Although it is preferable that the start of dropping of the polymerization initiator and the start of dropping of the second solution are simultaneous, they may be slightly changed as long as the effects of the present invention are not hindered.
The dropping of the second solution may be continuous or intermittent, and the dropping speed may be changed. In order to further stabilize the composition and molecular weight of the polymer produced, it is preferable to continuously drop the polymer at a constant rate.
When supplying a 1st solution by dripping, it may be continuous and may be intermittent, and dripping speed may change. In order to further stabilize the composition and molecular weight of the polymer produced, it is preferable to continuously drop the polymer at a constant rate.

When the first solution and the second solution are used, the period from the start of supply of the first solution into the reactor to the end of supply is a high-speed supply period of the monomer. Therefore, the supply of the first solution is terminated before 20% of the reference time has elapsed. For example, when the reference time is 4 hours, the entire amount of the first solution is fed into the reactor before 48 minutes have elapsed from the start of the addition of the polymerization initiator.
Further, the entire amount of the first solution may be supplied at the time of 0% of the reference time. That is, the entire amount of the first solution may be charged in the reactor before the start of dropping of the polymerization initiator.
The end of dropping of the polymerization initiator and the end of dropping of the second solution are preferably simultaneous, but may be slightly changed as long as the effects of the present invention are not hindered.

Further, when a value obtained by dividing the total supply amount of the polymerization initiator by the reference time is defined as an average supply rate Vj, a period from 0% to j% (j is 5 to 20) of the reference time is determined from the average supply rate Vj. Is a high-speed supply period of the polymerization initiator in which the polymerization initiator is dropped at a high speed.
The starting point of the high-speed supply period of the polymerization initiator is the start of the reference time, which is 0% of the reference time. The end point of the high-speed supply period of the polymerization initiator is a point when j% of the reference time has elapsed, and the j% is 5 to 20%, preferably 5.5 to 17.5%, and 6 to 15%. Is more preferable.
Either the end of the high-speed supply period of the polymerization initiator or the end of the high-speed supply period of the monomer may be first or simultaneously.
The dropping rate of the polymerization initiator during the high-speed supply period of the polymerization initiator may be higher than the average supply rate, and the dropping rate may be changed midway.
The dropping rate of the polymerization initiator after the end of the high-speed supply period of the polymerization initiator may be lower than the average supply rate, and the dropping rate may be changed in the middle, but the uniform polymer is stabilized. In order to obtain it, it is preferable to drop at a constant rate.

The initial stage of the polymerization process depends on the amount of polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator and the amount of monomer supplied into the reactor during the high-speed supply period of the monomer. The weight average molecular weight of the polymer produced in can be controlled.
In the present invention, the values of the weight average molecular weight of the polymer in the reactor after 30 minutes, 1 hour, and 2 hours from the start of dropping of the polymerization initiator (at the start of the reference time) are all finished. It controls so that it may become 80 to 120% of the weight average molecular weight of the polymer (P) at the time.
The end of the reaction is the time when the reaction is stopped by cooling the polymerization reaction solution in the reactor.

That is, after 30 minutes, 1 hour, 2 hours, and at the end of the reaction, the weight average molecular weight of the polymer in the reactor was measured, and after 30 minutes, 1 hour, or 2 hours. When the later measured value is larger than 120% of the weight average molecular weight at the end of the reaction, the conditions are changed so that the amount of the polymerization initiator supplied into the reactor is increased by the time of the measurement. On the other hand, if it is smaller than 80% of the weight average molecular weight at the end of the reaction, the amount of the polymerization initiator supplied into the reactor by the time of the measurement is reduced and / or the amount of the monomer Change the conditions so that there are more.
The optimum supply amount of the polymerization initiator during the high-speed supply period of the polymerization initiator varies depending on the type of monomer, the supply rate of the monomer, the type of polymerization initiator, the polymerization conditions, etc. 30 to 90 mass% of the total supply amount is preferable, and 35 to 85 mass% is more preferable.
In addition, the optimum monomer supply amount during the high-speed monomer supply period varies depending on the type of monomer, the type of polymerization initiator, the supply rate of the polymerization initiator, the polymerization conditions, etc. 2-50 mass% of the total supply amount of a monomer is preferable, 3-40 mass% is more preferable, and 5-30 mass% is further more preferable.

The following (a) and (b) are mentioned as a preferable aspect of the polymerization process in the case of using the first solution and the second solution.
(A) A reactor is charged with a first solution containing monomers α _{1 to} α _n in a first composition in advance, and the reactor is heated to a predetermined polymerization temperature. Inside, a polymerization initiator solution containing a part of the polymerization initiator and the monomers α _{1 to} α _n in the second composition and a second solution containing the remainder of the polymerization initiator are dropped. . Although either the polymerization initiator solution or the second solution may start dropping first, it is preferable to start dropping both solutions simultaneously. The interval between the start of dropping of the polymerization initiator solution and the start of dropping of the second solution is preferably 0 to 10 minutes.
The dropping speed is preferably constant. The polymerization initiator solution finishes dropping before the second solution.
In this embodiment, the start of the reference time, that is, the start of dropping of the polymerization initiator is at the start of dropping of the polymerization initiator solution and the second solution which has started to be dropped first. The end of the reference time is when the second solution is dropped. The end of dropping of the polymerization initiator is also at the end of dropping of the second solution.
In this embodiment, the entire amount of the first solution is supplied into the reactor before the start of dropping of the polymerization initiator. That is, the completion of the supply of the first solution is 0% of the reference time, and the high-speed supply period of the monomer is from 0% to 0%. The high-speed supply period of the polymerization initiator is a period during which the polymerization initiator solution is dripped.
The amount of monomer supplied into the reactor during the high-speed monomer supply period is the total amount of monomers contained in the first solution.
The amount of the polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator is dropped during the period when the polymerization initiator solution is dropped and the amount of the polymerization initiator contained in the polymerization initiator solution. This is the total amount of the polymerization initiator contained in the second solution.

(B) After charging only the solvent into the reactor and heating it to a predetermined polymerization temperature, the monomer α _{1 to} α _n are contained in the first composition, and the first containing a part of the polymerization initiator a solution, as well as containing monomer alpha ₁ to? _n in the second composition, is dropped respective second solution containing the remainder of the polymerization initiator. Both liquids start dropping simultaneously, or the first solution starts dropping first. The interval between the start of dropping of the first solution and the start of dropping of the second solution is preferably 0 to 10 minutes.
The dropping speed is preferably constant. The first solution finishes dropping before the second solution.
In this embodiment, the start of the reference time, that is, the dropping start of the polymerization initiator is at the start of dropping of the first solution. The end of the reference time is when the second solution is dropped. The end of dropping of the polymerization initiator is also at the end of dropping of the second solution.
The monomer high-speed supply period and the polymerization initiator high-speed supply period are both periods during which the first solution is dropped.
The amount of monomer supplied into the reactor during the high-speed monomer supply period is dropped during the period when the first solution and the amount of monomer contained in the first solution are dropped. This is the total amount of monomers contained in the second solution.
The amount of the polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator is dropped during the period when the amount of the polymerization initiator contained in the first solution and the first solution are dropped. This is the total amount of the polymerization initiator contained in the second solution.

According to the method of the present invention, the weight of the polymer in the reactor after 30 minutes, 1 hour, and 2 hours after the start of dropping of the polymerization initiator, as shown in Examples and Comparative Examples described later. The value of the average molecular weight can be controlled so as to be close to the weight average molecular weight of the polymer (P) at the end of the reaction, whereby the variation in the weight average molecular weight from immediately after the start of the polymerization reaction to the end of the reaction. Small polymers can be obtained.
Specifically, the value of the weight average molecular weight of the polymer in the reactor after 30 minutes, 1 hour, and 2 hours is 80 to 80% of the weight average molecular weight of the polymer (P) at the end of the reaction. It can be controlled to 120%, preferably 90 to 110%, whereby the weight average molecular weight from immediately after the start of the polymerization reaction to the end of the reaction is calculated as the weight average molecular weight of the polymer (P) at the end of the reaction. It can be 80 to 120%, preferably 90 to 110%.
Accordingly, variation in molecular weight is improved, solubility in a solvent is improved, and sensitivity when used in a resist composition is improved.
This is presumably because the formation of polymer molecules having an excessively high weight average molecular weight was suppressed by providing a monomer high-speed supply period and a polymerization initiator high-speed supply period early in the polymerization process.
Therefore, according to the present invention, the solubility in a solvent is good, and a polymer (P) having high sensitivity when used in a resist composition can be obtained with good reproducibility.

In addition, by using the first solution and the second solution in which the monomer content ratio is designed so as to obtain the steady state as the monomer solution, the target composition is almost the same as immediately after the start of the polymerization reaction. Polymer molecules of composition are produced and the state continues.
Therefore, the dispersion | variation in the content rate of the structural unit in the polymer (P) obtained after a superposition | polymerization process becomes small. This also contributes to improvement in solubility in a solvent and improvement in sensitivity when used in a resist composition.
In addition, the polymer of the present invention can be applied to uses other than resist applications, and an effect of improving solubility can be obtained, and improvement of various performances can be expected.

<Design method of first composition>
Hereinafter, a specific example of the design method of the first composition will be described.
When the content ratio (target composition, unit: mol%) of the structural unit in the polymer (P) to be obtained is α ′ ₁ : α ′ ₂ :...: Α ′ _n , the first composition (unit: Mol%) is represented by α ₁ : α ₂ :...: Α _n , and the factors determined by the following methods (1) to (3) are represented by F ₁ , F ₂ ,... F _n , α ₁ = α ′ ₁ / F ₁ , α ₂ = α ′ ₂ / F ₂ ,... Α _n = α ′ _n / F _n are preferable.
(1) First monomer composition target composition _{α '1: α' 2:} ...: α ' dropping a solution containing the monomer mixture 100 parts by weight of the same as the polymerization initiator solvent is _n, a solvent alone Are added at a constant dropping rate, and when the elapsed time from the start of dropping is t ₁ , t ₂ , t ₃ ..., The monomers α ₁ to. Composition of α _n (unit: mol%) M ₁ : M ₂ :...: M _n and a structural unit in the polymer formed between t ₁ and t ₂ , between t ₂ and t ₃ ,. The ratio of α ′ _{1 to} α ′ _n (unit: mol%) P ₁ : P ₂ :...: P _n is determined.
(2) the _{P 1: P 2: ...:} P n is, target composition _{α '1: α' 2:} ...: α ' between the closest time zone _n from _{"t m} to _{t m + 1} (m is 1 or more Find an integer.)
(3) From the value of P ₁ : P ₂ :...: P _n in “between t _m and t _{m + 1} ” and the value of M ₁ : M ₂ :...: M _{n at} the elapsed time t _m , Factors F ₁ , F ₂ ,... F _n are obtained from the equations. F ₁ = P ₁ / M ₁ , F ₂ = P ₂ / M ₂ ,... F _n = P _n / M _n .

More specifically, for example, the polymer (P) is a ternary polymer obtained by copolymerizing the monomers x, y, and z, and the target composition is x ′: y ′: When z ′, the first composition (mol%, the same shall apply hereinafter) x ₀ : y ₀ : z ₀ is obtained by using the factors Fx, Fy and Fz obtained by the following method, and x ₀ = x ′ / It is assumed that Fx, y ₀ = y ′ / Fy, z ₀ = z ′ / Fz.

[How to find factors Fx, Fy, Fz]
Hereinafter, the case where the polymer (P) is a ternary polymer will be described as an example, but the factor can be obtained in the same manner for a binary system or a quaternary system or more.
(1) First, a dropping solution containing a monomer mixture having the same monomer composition as the target composition x ′: y ′: z ′, a solvent, and a polymerization initiator is placed in a reactor at a constant dropping rate v. Add dropwise. Only the solvent is put in the reactor in advance.
When the elapsed time from the start of dropping is t ₁ , t ₂ , t ₃ ..., The composition (mol%) Mx: My: Mz of the monomers x, y, z remaining in the reactor, between t ₁ to _{t 2,} the ratio of the structural unit in the polymer produced respectively between ... to from _{t 2} to _{t 3} (mol%) Px: Py: Request Pz.
(2) Find the time zone “between t _m and t _{m + 1} (m is an integer of 1 or more)” where Px: Py: Pz is closest to the target composition x ′: y ′: z ′.
(3) From the value of Px: Py: Pz in “between t _m and t _{m + 1} ” and the value of Mx: My: Mz at the elapsed time t _m , the factors Fx, Fy, and Fz are calculated by the following equation. Ask.
Fx = Px / Mx, Fy = Py / My, Fz = Pz / Mz.
The factors Fx, Fy, and Fz are values that reflect the relative reactivity of each monomer, and change when the combination of monomers used for polymerization or the target composition changes.

(4) Preferably, the proportion of the total mass of the monomers present in the reactor in the elapsed time t _m out of 100% by mass of the monomer mixture contained in the first dropping solution ( (W ₀ % by mass).
When the first solution and the second solution are used as the monomer solution, the ratio of the total amount of monomers contained in the first solution to the total supply amount of the monomers is represented by W ₀ mass. %, Polymer molecules having the same composition as the target composition are likely to be generated immediately after the start of the polymerization reaction.

<Resist composition>
The resist composition of the present invention is prepared by dissolving the lithographic polymer of the present invention in a resist solvent. Examples of the resist solvent include the same solvents as those used for the production of the polymer.
When the resist composition of the present invention is a chemically amplified resist composition, a compound that generates an acid upon irradiation with actinic rays or radiation (hereinafter referred to as a photoacid generator) is further contained.

(Photoacid generator)
The photoacid generator can be arbitrarily selected from known photoacid generators in the chemically amplified resist composition. A photo-acid generator may be used individually by 1 type, and may use 2 or more types together.
Examples of the photoacid generator include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonic acid ester compounds, quinone diazide compounds, diazomethane compounds, and the like.
0.1-20 mass parts is preferable with respect to 100 mass parts of polymers, and, as for content of the photo-acid generator in a resist composition, 0.5-10 mass parts is more preferable.

(Nitrogen-containing compounds)
The chemically amplified resist composition may contain a nitrogen-containing compound. By including the nitrogen-containing compound, the resist pattern shape, the stability over time, and the like are further improved. That is, the cross-sectional shape of the resist pattern becomes closer to a rectangle. In a mass production line for semiconductor elements, the resist film is irradiated with light, then baked (PEB), and then left for several hours before the next development process. Occurrence of deterioration of the cross-sectional shape of the resist pattern due to is further suppressed.
The nitrogen-containing compound is preferably an amine, more preferably a secondary lower aliphatic amine or a tertiary lower aliphatic amine.
As for content of the nitrogen-containing compound in a resist composition, 0.01-2 mass parts is preferable with respect to 100 mass parts of polymers.

(Organic carboxylic acid, phosphorus oxo acid or its derivative)
The chemically amplified resist composition may contain an organic carboxylic acid, an oxo acid of phosphorus, or a derivative thereof (hereinafter collectively referred to as an acid compound). By including an acid compound, it is possible to suppress deterioration in sensitivity due to the blending of the nitrogen-containing compound, and further improve the resist pattern shape, stability with time of leaving, and the like.
Examples of the organic carboxylic acid include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.
Examples of phosphorus oxo acids or derivatives thereof include phosphoric acid or derivatives thereof, phosphonic acid or derivatives thereof, phosphinic acid or derivatives thereof, and the like.
The content of the acid compound in the resist composition is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the polymer.

(Additive)
The resist composition of the present invention may contain various additives such as surfactants, other quenchers, sensitizers, antihalation agents, storage stabilizers, and antifoaming agents as necessary. Any additive can be used as long as it is known in the art. Further, the amount of these additives is not particularly limited, and may be determined as appropriate.

<Manufacturing method of substrate on which pattern is formed>
An example of the manufacturing method of the board | substrate with which the pattern was formed of this invention is demonstrated.
First, the resist composition of the present invention is applied by spin coating or the like on a processed surface of a substrate such as a silicon wafer on which a desired fine pattern is to be formed. And the resist film is formed on a board | substrate by drying the board | substrate with which this resist composition was apply | coated by baking process (prebaking) etc.
Next, the resist film is exposed through a photomask to form a latent image. The exposure light is preferably light having a wavelength of 250 nm or less. For example, KrF excimer laser, ArF excimer laser, F ₂ excimer laser and EUV light are preferable, and ArF excimer laser is particularly preferable. Moreover, you may irradiate an electron beam.
In addition, immersion in which light is irradiated with a high refractive index liquid such as pure water, perfluoro-2-butyltetrahydrofuran, or perfluorotrialkylamine interposed between the resist film and the final lens of the exposure apparatus. Exposure may be performed.

After exposure, heat treatment is appropriately performed (post-exposure baking, PEB), an alkali developer is brought into contact with the resist film, and the exposed portion is dissolved in the developer and removed (development). Examples of the alkaline developer include known ones.
After development, the substrate is appropriately rinsed with pure water or the like. In this way, a resist pattern is formed on the substrate.
The substrate on which the resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist and selectively etch the portion without the resist.
After the etching, the resist is removed with a release agent to obtain a substrate on which a fine pattern is formed.

The polymer for lithography obtained by the production method of the present invention is excellent in solubility in a solvent and can form a highly sensitive resist film.
Therefore, it is possible to easily and satisfactorily dissolve the polymer in the resist solvent when preparing the resist composition. In addition, the resist composition has excellent solubility in an alkali developer and contributes to an improvement in sensitivity. In addition, since the insoluble content in the resist composition is small, defects due to the insoluble content are less likely to occur during pattern formation.
Therefore, according to the method for producing a substrate of the present invention, by using the resist composition of the present invention, a highly accurate fine resist pattern with few defects can be stably formed on the substrate. In addition, pattern formation by photolithography using an exposure light having a wavelength of 250 nm or less or lithography using an electron beam lithography such as ArF excimer laser (193 nm), which requires the use of a resist composition with high sensitivity and high resolution, is also required. It can be used suitably.
In the case of producing a resist composition used for photolithography using exposure light having a wavelength of 250 nm or less, a monomer is appropriately selected and used so that the polymer is transparent at the wavelength of the exposure light. Is preferred.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, “part” in each example and comparative example means “part by mass” unless otherwise specified. The measurement method and evaluation method used the following methods.

(Measurement of weight average molecular weight)
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer were determined in terms of polystyrene by gel permeation chromatography under the following conditions (GPC conditions).
[GPC conditions]
Equipment: Tosoh Corporation, Tosoh High Speed GPC Equipment HLC-8220GPC (trade name),
Separation column: manufactured by Showa Denko, Shodex GPC K-805L (trade name) connected in series,
Measurement temperature: 40 ° C.
Eluent: Tetrahydrofuran (THF)
Sample (in the case of a polymer): a solution in which about 20 mg of a polymer is dissolved in 5 mL of THF and filtered through a 0.5 μm membrane filter,
Sample (in the case of polymerization reaction solution): A solution in which about 30 mg of the sampled polymerization reaction solution was dissolved in 5 mL of THF and filtered through a 0.5 μm membrane filter. Flow rate: 1 mL / min.
Injection volume: 0.1 mL,
Detector: differential refractometer.

Calibration curve I: About 20 mg of standard polystyrene was dissolved in 5 mL of THF, and the solution was filtered through a 0.5 μm membrane filter and injected into a separation column under the above conditions, and the relationship between elution time and molecular weight was determined. As the standard polystyrene, the following standard polystyrene manufactured by Tosoh Corporation (both trade names) were used.
F-80 (Mw = 706,000),
F-20 (Mw = 190,000),
F-4 (Mw = 37,900),
F-1 (Mw = 10,200),
A-2500 (Mw = 2,630),
A-500 (mixture of Mw = 682, 578, 474, 370, 260).

(Quantification of monomer)
The amount of monomer remaining in the polymerization reaction solution was determined by the following method.
0.5 g of the polymerization reaction solution in the reactor was collected, diluted with acetonitrile, and the total volume was adjusted to 50 mL using a volumetric flask. The diluted solution was filtered through a 0.2 μm membrane filter, and the amount of unreacted monomer in the diluted solution was determined for each monomer using a high performance liquid chromatograph HPLC-8020 (product name) manufactured by Tosoh Corporation. Asked.

  In this measurement, a separation column is manufactured by GL Sciences, and one Inertsil ODS-2 (trade name) is used. The mobile phase is a water / acetonitrile gradient system, the flow rate is 0.8 mL / min, and the detector is manufactured by Tosoh Corporation. Ultraviolet / visible absorptiometer UV-8020 (trade name), detection wavelength 220 nm, measurement temperature 40 ° C., injection amount 4 μL. The separation column Inertsil ODS-2 (trade name) used was a silica gel particle diameter of 5 μm, a column inner diameter of 4.6 mm × column length of 450 mm. The gradient conditions of the mobile phase were as follows, with the liquid A being water and the liquid B being acetonitrile. In order to quantify the amount of unreacted monomer, three types of monomer solutions having different concentrations were used as standard solutions.

Measurement time 0 to 3 minutes: A liquid / B liquid = 90 vol% / 10 vol%.
Measurement time: 3 to 24 minutes: A liquid / B liquid = 90 volume% / 10 volume% to 50 volume% / 50 volume%.
Measurement time: 24 to 36.5 minutes: A liquid / B liquid = 50 volume% / 50 volume% to 0 volume% / 100 volume%.
Measurement time: 36.5 to 44 minutes: Liquid A / liquid B = 0 volume% / 100 volume%.

(Evaluation of polymer solubility)
20 parts of the polymer and 80 parts of PGMEA were mixed and stirred while maintaining at 25 ° C., and complete dissolution was judged visually, and the time until complete dissolution was measured.

(Evaluation of resist composition sensitivity)
The resist composition was spin-coated on a 6-inch silicon wafer and pre-baked (PAB) at 120 ° C. for 60 seconds on a hot plate to form a resist film having a thickness of 300 nm. Using an ArF excimer laser exposure apparatus (product name: VUVES-4500, manufactured by RISOTEC JAPAN), 18 shots having an area of 10 mm × 10 mm were exposed while changing the exposure amount. Next, after post-baking (PEB) at 110 ° C. for 60 seconds, 2.38% tetrahydroxide at 23.5 ° C. using a resist development analyzer (product name: RDA-806, manufactured by RISOTEC JAPAN). Developed with aqueous methylammonium solution for 65 seconds. For each exposure amount of the resist film, the change with time in the resist film thickness during development was measured.
Based on the data of change in resist film thickness over time, the logarithm of the exposure amount (unit: mJ / cm ² ) and the ratio of the remaining film thickness at the time of development for 30 seconds with respect to the initial film thickness (unit:%). , Hereinafter referred to as the residual film ratio) was plotted, and an exposure amount-residual film ratio curve was prepared. Based on this curve, the value of the necessary exposure amount (Eth) for obtaining a remaining film rate of 0% was determined. That is, the exposure amount (mJ / cm ² ) at the point where the exposure amount-residual film rate curve intersects a straight line with a residual film rate of 0% was determined as Eth. The value of Eth represents sensitivity, and the smaller the value, the higher the sensitivity.

<Reference Example 1: Design of first composition>
In this example, monomers m-1, m-2 and m-3 represented by the following formulas (m-1), (m-2) and (m-3) are polymerized, and the target composition is m. −1: m−2: m−3 = 40: 40: 20 (mol%), an example in which the first composition was obtained in the case of producing a polymer having a weight average molecular weight target value of 10,000. .
The polymerization initiator used in this example is dimethyl-2,2′-azobisisobutyrate (V601 (trade name)). The polymerization temperature was 80 ° C.

In a flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer, 67.8 parts of ethyl lactate was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the flask.
Thereafter, a dropping solution (total amount: 205.725 g) containing the following monomer mixture, solvent, and polymerization initiator was prepared, and this was dropped into the flask at a constant dropping rate over 4 hours from the dropping funnel. Furthermore, the temperature of 80 degreeC was hold | maintained for 3 hours. Seven hours after the start of dropping of the dropping solution, the reaction was stopped by cooling to room temperature.
28.56 parts (40 mol%) of monomer m-1;
32.93 parts (40 mol%) of monomer m-2,
19.82 parts (20 mol%) of monomer m-3,
122.0 parts ethyl lactate,
2.415 parts of dimethyl-2,2′-azobisisobutyrate (2.5 mol% with respect to the total monomer feed).

  After 0.5, 1, 2, 3, 4, 5, 6, 7 hours from the start of the dropping of the dropping solution, 0.5 g of the polymerization reaction solution in each flask was sampled, and monomers m-1 to m- Three quantifications were performed respectively. Thereby, the mass of each monomer remaining in the reactor at the time of each sampling is known. As a result, for example, the results after 2 hours and 3 hours after the start of dropping were as shown in Table 1.

Next, the molecular weight of each monomer was used to convert the molar fraction of each monomer remaining in the reactor at each sampling time (corresponding to Mx: My: Mz).
As a result, for example, the results 2 hours and 3 hours after the start of dropping were as shown in Table 2.

On the other hand, the total mass of each monomer supplied by each sampling is obtained from the mass (total supply amount) of each monomer supplied to the reactor at a constant rate for 4 hours. By subtracting the mass of each monomer remaining in the vessel, the mass of each monomer that had been converted to a polymer was calculated for each monomer at the time of each sampling. .
Subsequently, by taking the difference data, the mass converted to the polymer between the sampling time and the sampling time was determined for each monomer, and converted into a mole fraction. The value of this mole fraction is the polymer produced during each sampling, that is, the elapsed time from the dropping (reaction time) from t ₁ to t ₂ , from t ₂ to t ₃ , and so on. The content ratio of structural units in each polymer produced (hereinafter sometimes referred to as polymer composition ratio) corresponds to Px: Py: Pz.
The obtained results are shown in FIG. The horizontal axis in FIG. 1 shows the reaction time on the end side of each reaction time zone (between sampling and sampling). That is, in FIG. 1, the data when the reaction time on the horizontal axis is 3 hours corresponds to the data of the polymer produced 2 to 3 hours after the start of dropping (the same applies hereinafter).

Moreover, about the polymerization reaction solution sampled at each reaction time, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were calculated | required by GPC measurement. The results are shown in Table 3 and FIG. Table 3 shows the ratio (unit:%) of the measured value of Mw in each reaction time when the weight average molecular weight (Mw) at the end of the reaction (7 hours after the start of the reaction) is 100%. Shown (the same applies hereinafter).
The reaction time in Table 3 and FIG. 2 indicates the reaction time on the end side of each reaction time zone (between sampling and sampling). That is, the data when the reaction time is 3 hours corresponds to the data of the polymer produced 2 to 3 hours after the start of dropping (hereinafter the same).

As shown in the results of FIG. 1, the polymer composition ratio (Px: Py: Pz) is closest to the target composition of 40:40:20, which is generated 2 hours to 3 hours after the start of dropping. It was a polymer, and Px: Py: Pz = 41.05: 38.47: 20.48.
Using this value and the value of Mx: My: Mz after 2 hours from the start of dropping (Table 2), Fx = Px / Mx, Fy = Py / My, Fz = Pz / Mz, factor Fx , Fy, and Fz are obtained as Fx = 1.27, Fy = 0.76, and Fz = 1.22.
The first composition x ₀ : y ₀ : z ₀ was determined using the factor value and the target composition.
_{x 0 = 40 / Fx = 40} / 1.27 = 31.3 mole%.
_{y 0 = 40 / Fy = 40} / 0.76 = 52.4 mole%.
_{z 0 = 20 / Fz = 20} / 1.22 = 16.3 mole%.

[Calculation of W ₀ ]
When the monomer mixture (total 81.31 parts) contained in the first dropping solution is 100% by mass, the total mass of the monomers present in the reactor after 2 hours from the start of dropping. The ratio (W ₀ ) occupied by (14.13 parts from Table 1) is 17.4% by mass.

<Example 1>
In this example, using the first composition obtained in Reference Example 1, a polymer was produced by the method (a) according to the present invention. The type of monomer used, the type of polymerization initiator, the polymerization temperature, the target composition of the polymer, and the target value of the weight average molecular weight are the same as in Reference Example 1.
The following 1st solution was put into the flask provided with the nitrogen inlet, the stirrer, the condenser, the two dropping funnels, and the thermometer under nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the flask.
Then, the following 2nd solution is dripped in a flask over 4 hours from a dropping funnel, the temperature of 80 degreeC is hold | maintained for 3 hours, and it cools to room temperature 7 hours after the dripping start of a 2nd solution. The reaction was stopped. Simultaneously with the start of dropping of the second solution, the following polymerization initiator solution was dropped into the flask from another dropping funnel over 0.25 hours.
Of the total supply amount of the monomers, the amount of monomers to be contained in the first solution was 17.4 wt% from W ₀ of Reference Example 1.
In this example, the reference time is 4 hours, and the period during which the polymerization initiator solution is dropped (0.25 hour) is the high-speed supply period of the polymerization initiator. That is, the high-speed supply period (0 to j%) of the polymerization initiator is 0 to 6.25% (j = 6.25%) of the reference time. The polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator is about 65% by mass of the total supply amount of the polymerization initiator.
The high-speed monomer supply period (0 to k%) is 0 to 0% (k = 0%) of the reference time. The amount of monomer supplied into the reactor during the high-speed monomer supply period is 17.4% by mass (= W ₀ ) of the total monomer supply amount.

(First solution)
3.87 parts (31.3 mol%) of monomer m-1
7.46 parts (52.4 mol%) of monomer m-2,
2.80 parts (16.3 mol%) of monomer m-3,
96.5 parts ethyl lactate.
(Second solution)
23.34 parts (40 mol%) of monomer m-1;
26.91 parts (40 mol%) of monomer m-2,
16.20 parts (20 mol%) of monomer m-3,
98.9 parts ethyl lactate,
0.670 parts of dimethyl-2,2′-azobisisobutyrate (0.7 mol% based on the total amount of monomers supplied).
(Polymerization initiator solution)
1.9 parts of ethyl lactate,
1.243 parts of dimethyl-2,2′-azobisisobutyrate (1.3 mol% based on the total amount of monomers supplied).

In the same procedure as in Reference Example 1, the content ratio (polymer composition ratio) of the constituent units in the polymer produced during each reaction time was determined. The result is shown in FIG.
Moreover, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were calculated | required about the polymerization reaction solution sampled at each reaction time like the reference example 1. FIG. The results are shown in Table 4 and FIG.

Comparing the results of FIG. 1 and FIG. 3, in Reference Example 1 (FIG. 1), the polymer composition ratio of the polymer produced immediately after the start of dripping is significantly different from the target composition, and the polymer composition depends on the reaction time. Variation is large.
On the other hand, in Example 1 (FIG. 3) in which the first solution was previously charged in the flask, the polymer composition ratio was almost the same as the target composition immediately after the start of dropping, and the composition ratio of the reaction time was Variability was also improved. In particular, the polymer composition ratio of the polymer obtained by the reaction time of 4 hours in which the dropping was continued is small from the target composition.

Further, comparing the results of FIG. 2 and FIG. 4, in Reference Example 1 (FIG. 2), especially the weight average molecular weight from the start of dropping to 3 hours is greatly different from the subsequent weight average molecular weight, and it varies depending on the reaction time. Is also big.
On the other hand, in Example 1 (FIG. 4), the dispersion of the weight average molecular weight and molecular weight distribution depending on the reaction time is small from immediately after the start of dropping until the end of the reaction.

[Purification of polymer]
After 7 hours of reaction time, the reaction was stopped by cooling to room temperature, and the polymerization reaction solution in the flask was mixed with about 10 times the amount of methanol and water mixed solvent (methanol / water = 80/20 volume ratio). The solution was added dropwise with stirring to obtain a white precipitate (polymer P1). The precipitate was filtered off and again poured into a mixed solvent of methanol and water in the same amount as above (methanol / water = 90/10 volume ratio), and the precipitate was washed with stirring. And the precipitate after washing | cleaning was separated by filtration, and 160 g of polymer wet powder was obtained. 10 g of the polymer wet powder was dried at 40 ° C. under reduced pressure for about 40 hours. About the obtained polymer P1, Mw and Mw / Mn were calculated | required and solubility was evaluated. The results are shown in Table 10.

[Production of resist composition]
The rest of the polymer wet powder is put into 880 g of PGMEA and completely dissolved to obtain a polymer solution, and then a nylon filter having a pore size of 0.04 μm (P-NYLON N66FILTER 0.04M manufactured by Nippon Pole Co., Ltd. (product) The polymer solution was filtered.
The obtained polymer solution was heated under reduced pressure to distill off methanol and water, and further PGMEA was distilled off to obtain a polymer P1 solution having a polymer concentration of 25% by mass. At this time, the maximum ultimate vacuum was 0.7 kPa, the maximum solution temperature was 65 ° C., and the distillation time was 8 hours.

  400 parts of the obtained polymer P1 solution, 2 parts of triphenylsulfonium triflate as a photoacid generator, and PGMEA as a solvent were mixed so that the polymer concentration was 12.5% by mass. After preparing a uniform solution, the solution was filtered through a membrane filter having a pore size of 0.1 μm to obtain a resist composition. The sensitivity of the obtained resist composition was evaluated by the above method. The results are shown in Table 10.

<Example 2>
In this example, a polymer was produced by the method (b) according to the present invention using the first composition obtained in Reference Example 1. The type of monomer used, the type of polymerization initiator, the polymerization temperature, the target composition of the polymer, and the target value of the weight average molecular weight are the same as in Reference Example 1.
A flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer was charged with 86.5 parts of ethyl lactate under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the flask.
Then, the following 2nd solution is dripped in a flask over 4 hours from a dropping funnel, the temperature of 80 degreeC is hold | maintained for 3 hours, and it cools to room temperature 7 hours after the dripping start of a 2nd solution. The reaction was stopped. Simultaneously with the start of dropping of the second solution, the following first solution was dropped into the flask from another dropping funnel over 0.25 hours.
Of the total supply amount of the monomers, the amount of monomers to be contained in the first solution was 17.4 wt% from W ₀ of Reference Example 1.
In this example, the reference time is 4 hours, and the period during which the first solution is dropped (0.25 hour) is the high-speed supply period of the monomer and the polymerization initiator. That is, the high-speed supply period (0 to j%) of the polymerization initiator is 0 to 6.25% (j = 6.25%) of the reference time, and the high-speed supply period (0 to k%) of the monomer is also used. It is 0 to 6.25% of the reference time (k = 6.25%). The polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator is the same as in Example 1, and is about 65% by mass of the total supply amount of the polymerization initiator. Further, the amount of the monomer supplied into the reactor during the high-speed monomer supply period is 22.7% by mass of the total monomer supply amount.

(First solution)
3.87 parts (31.3 mol%) of monomer m-1
7.46 parts (52.4 mol%) of monomer m-2,
2.80 parts (16.3 mol%) of monomer m-3,
11.9 parts of ethyl lactate,
1.243 parts of dimethyl-2,2′-azobisisobutyrate (1.3 mol% based on the total amount of monomers supplied).
(Second solution)
23.34 parts (40 mol%) of monomer m-1;
26.91 parts (40 mol%) of monomer m-2,
16.20 parts (20 mol%) of monomer m-3,
98.9 parts ethyl lactate,
0.670 parts of dimethyl-2,2′-azobisisobutyrate (0.7 mol% based on the total amount of monomers supplied).

In the same procedure as in Reference Example 1, the composition ratio (polymer composition ratio) of the constituent units in the polymer produced during each reaction time was determined. The result is shown in FIG.
Moreover, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were calculated | required about the polymerization reaction solution sampled at each reaction time like the reference example 1. FIG. The results are shown in Table 5 and FIG.

As shown in the results of FIG. 5, in this example as well as in Example 1, the polymer composition ratio was almost the same as the target composition immediately after the start of dropping, and the variation in the composition ratio due to the reaction time was also improved. In particular, the composition ratio of the polymer obtained by the reaction time of 4 hours in which the dropping was continued is small from the target composition.
Also, as shown in the results of FIG. 6, in this example as well as in Example 1, the variation in the weight average molecular weight and molecular weight distribution depending on the reaction time is small from immediately after the start of dropping until the end of the reaction.

[Purification of polymer]
In the same manner as in Example 1, polymer P2 was obtained from the polymerization reaction solution in the flask after 7 hours of reaction time. Table 10 shows the results of Mw, Mw / Mn, and solubility evaluation of the polymer P2.
[Production of resist composition]
In the same manner as in Example 1, a resist composition containing the polymer P2 was prepared, and the sensitivity was evaluated. The results are shown in Table 10.

<Reference Example 2: Design of first composition>
In this example, monomers m-4, m-5, and m-6 represented by the following formulas (m-4), (m-5), and (m-6) are polymerized, and the target composition is m. -4: m-5: m-6 = 40: 40: 20 (% by mole) This is an example in which the first composition is obtained when a polymer having a weight average molecular weight target value of 10,000 is produced. .
The same dimethyl-2,2′-azobisisobutyrate as in Reference Example 1 was used as the polymerization initiator, and the polymerization temperature was 80 ° C.

In a flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer, 70.6 parts of propylene glycol monomethyl ether acetate (PGMEA) was placed under a nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the flask.
Thereafter, a dropping solution (total amount 220.612 g) containing the following monomer mixture, solvent, and polymerization initiator was prepared, and this was dropped into the flask at a constant dropping rate over 4 hours from the dropping funnel. Furthermore, the temperature of 80 degreeC was hold | maintained for 3 hours. Seven hours after the start of dropping of the dropping solution, the reaction was stopped by cooling to room temperature.
26.83 parts (40 mol%) of monomer m-4,
40.25 parts (40 mol%) of monomer m-5,
17.63 parts (20 mol%) of monomer m-6,
127.1 parts of PGMEA,
8.802 parts of dimethyl-2,2′-azobisisobutyrate (8.9 mol% with respect to the total monomer feed).

  After 0.5, 1, 2, 3, 4, 5, 6, 7 hours from the start of the dropping of the dropping solution, 0.5 g of the polymerization reaction solution in each flask was sampled, and monomers m-4 to m- Each of the 6 quantifications was performed. Thereby, the mass of each monomer remaining in the reactor at the time of each sampling is known. As a result, for example, the results after 1 hour and 2 hours after the start of dropping were as shown in Table 6.

Next, the molecular weight of each monomer was used to convert the molar fraction of each monomer remaining in the reactor at each sampling time (corresponding to Mx: My: Mz).
As a result, for example, the results after 1 hour and 2 hours after the start of dropping were as shown in Table 7.

On the other hand, in the same manner as in Reference Example 1, the content ratio of the constituent units (polymer composition ratio, Px: Py: Pz) in the polymer produced during each reaction time was determined. The obtained results are shown in FIG.
Moreover, Mw and Mw / Mn were calculated | required about the polymerization reaction solution sampled at each reaction time. The results are shown in Table 8 and FIG.

As shown in the results of FIG. 7, the polymer composition ratio (Px: Py: Pz) is closest to the target composition of 40:40:20, which is generated 1 hour to 2 hours after the start of dropping. The polymer was Px: Py: Pz = 40.07: 39.95: 19.99.
Using this value and the value of Mx: My: Mz (Table 7) after 2 hours from the start of dropping, Fx = Px / Mx, Fy = Py / My, Fz = Pz / Mz, and factor Fx , Fy, and Fz are obtained as Fx = 0.80, Fy = 1.10, and Fz = 1.42.
The first composition x ₀ : y ₀ : z ₀ was determined using the factor value and the target composition.
_{x 0 = 40 / Fx = 40} / 0.80 = 49.8 mol%.
_{y 0 = 40 / Fy = 40} / 1.10 = 36.2 mole%.
_{z 0 = 20 / Fz = 20} / 1.42 = 14.0 mole%.

[Calculation of W ₀ ]
Assuming that the monomer mixture (total 84.71 parts) contained in the first dropping solution is 100% by mass, the total mass of monomers present in the reactor after 1 hour has elapsed since the start of dropping. The ratio (W ₀ ) occupied by (6.40 parts from Table 6) is 7.6% by mass.

<Example 3>
In this example, a polymer was produced by the method (a) according to the present invention using the first composition obtained in Reference Example 2. The type of monomer used, the type of polymerization initiator, the polymerization temperature, the target composition of the polymer, and the target weight average molecular weight are the same as in Reference Example 2.
The following 1st solution was put into the flask provided with the nitrogen inlet, the stirrer, the condenser, the two dropping funnels, and the thermometer under nitrogen atmosphere. The flask was placed in a hot water bath, and the temperature of the hot water bath was raised to 80 ° C. while stirring the flask.
Then, the following 2nd solution is dripped in a flask over 4 hours from a dropping funnel, the temperature of 80 degreeC is hold | maintained for 3 hours, and it cools to room temperature 7 hours after the dripping start of a 2nd solution. The reaction was stopped. Simultaneously with the start of dropping of the second solution, the following polymerization initiator solution was dropped into the flask from another dropping funnel over 0.25 hours.
Of the total supply amount of monomers, the amount of monomers to be contained in the first solution was 7.6% by mass from W _{0 of} Reference Example 2.
In this example, the reference time is 4 hours, and the period during which the polymerization initiator solution is dropped (0.25 hour) is the high-speed supply period of the polymerization initiator. That is, the high-speed supply period (0 to j%) of the polymerization initiator is 0 to 6.25% (j = 6.25%) of the reference time. The polymerization initiator supplied into the reactor during the high-speed supply period of the polymerization initiator is about 55% by mass of the total supply amount of the polymerization initiator.
The high-speed monomer supply period (0 to k%) is 0 to 0% (k = 0%) of the reference time. The amount of monomer supplied into the reactor during the high-speed monomer supply period is 7.6% by mass (= W ₀ ) of the total monomer supply amount.

(First solution)
2.60 parts (49.8 mol%) of monomer m-4,
2.84 parts (36.2 mol%) of monomer m-5,
0.96 part (14.0 mol%) of monomer m-6.
80.2 parts PGMEA.
(Second solution)
Monomer m-4 24.80 parts (40 mol%),
37.21 parts (40 mol%) of monomer m-5,
16.30 parts (20 mol%) of monomer m-6,
110.0 parts of PGMEA,
3.456 parts of dimethyl-2,2′-azobisisobutyrate (3.49 mol% with respect to the total monomer feed).
(Polymerization initiator solution)
7.5 parts of PGMEA,
4.2224 parts of dimethyl-2,2′-azobisisobutyrate (4.26 mol% with respect to the total monomer feed).

In the same procedure as in Reference Example 2, the content ratio (polymer composition ratio) of the constituent units in the polymer produced during each reaction time was determined. The result is shown in FIG.
In the same manner as in Reference Example 2, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined for the polymerization reaction solution sampled at each reaction time. The results are shown in Table 9 and FIG.

Comparing the results of FIG. 7 and FIG. 9, in Reference Example 2 (FIG. 7), the polymer composition ratio of the polymer produced immediately after the start of dripping is significantly different from the target composition, and the polymer composition depends on the reaction time. Variation is large.
On the other hand, in Example 3 (FIG. 8) in which the first solution was previously charged in the flask, the polymer composition ratio was almost the same as the target composition immediately after the start of dropping, and the composition ratio by the combination reaction time. Variability was also improved. In particular, the polymer composition ratio of the polymer obtained by the reaction time of 4 hours in which the dropping was continued is small from the target composition.

Further, comparing the results of FIG. 8 and FIG. 10, in Reference Example 2 (FIG. 8), the difference in weight average molecular weight from the start of dripping to 3 hours, in particular, is large due to the reaction time. Is also big.
On the other hand, in Example 3 (FIG. 10), the variation in the weight average molecular weight and molecular weight distribution due to the reaction time is small from immediately after the start of dropping until the end of the reaction.

[Purification of polymer]
A mixed solvent of methanol and water (methanol / water = 80/20 volume ratio) and (methanol / water = 90/10 volume ratio) used in the purification process of the polymer of Example 1 were mixed with methanol and water, respectively. Polymerization reaction in the flask after a reaction time of 7 hours in the same manner as in Example 1 except that the solvent (methanol / water = 90/10 volume ratio) and (methanol / water = 95/5 volume ratio) were changed. From the solution, a polymer P3 was obtained. Table 10 shows the results of Mw, Mw / Mn, and solubility evaluation of the polymer P3.
[Production of resist composition]
In the same manner as in Example 1, a resist composition containing the polymer P3 was prepared, and the sensitivity was evaluated. The results are shown in Table 10.

<Comparative Example 1>
In Reference Example 1, after the reaction time of 7 hours had elapsed, the polymerization reaction solution in the flask obtained by cooling to room temperature to stop the reaction was used, and the comparative weight was determined in the same manner as in the polymer purification step of Example 1. Combined 1 was obtained. About the obtained comparative polymer 1, Mw and Mw / Mn were calculated | required similarly to Example 1, and solubility evaluation was performed.
Moreover, using the comparative polymer 1, a resist composition was prepared in the same manner as in Example 1, and the sensitivity was evaluated. The results are shown in Table 10.

<Comparative Example 2>
In Reference Example 2, after the reaction time of 7 hours had elapsed, the polymerization reaction solution in the flask obtained by cooling to room temperature to stop the reaction was used, and the comparative weight was determined in the same manner as in the polymer purification step of Example 3. Combined 2 was obtained. About the obtained comparative polymer 2, it carried out similarly to Example 3, calculated | required Mw and Mw / Mn, and performed solubility evaluation.
Further, using the comparative polymer 2, a resist composition was prepared in the same manner as in Example 3, and the sensitivity was evaluated. The results are shown in Table 10.

  From the results of Table 10, the polymers obtained in Examples 1, 2, and 3 have significantly improved solubility as compared with the polymers obtained in Comparative Examples 1 and 2, respectively, and when the resist composition was obtained. Sensitivity improved.

Claims (5)

While dropping a monomer and a polymerization initiator in the reactor, two or more monomers α _{1 to} α _n (where n represents an integer of 2 or more) are polymerized in the reactor. And a polymerization step for obtaining a polymer (P) comprising the structural units α ′ _{1 to} α ′ _n (where α ′ _{1 to} α ′ _n represent structural units derived from the monomers α _{1 to} α _n , respectively). Have
The monomer is a (meth) acrylic acid ester, and the polymerization initiator is a radical polymerization initiator that is an azo compound,
Start supplying the monomer solution containing the monomers α _{1 to} α _n into the reactor before dropping the polymerization initiator into the reactor or simultaneously with the dropping of the polymerization initiator. And
When the reference time is from the start of dropping of the polymerization initiator to the end of dropping of the monomer solution, the reference time is 2 hours or more,
When a value obtained by dividing the total supply amount of the polymerization initiator by the reference time is defined as an average supply rate Vj, a period from 0% to j% (j is 5 to 20) of the reference time is defined as the average supply rate. A high-speed supply period of the polymerization initiator that drops the polymerization initiator at a higher speed than Vj,
When the average supply rate Vk is a value obtained by dividing the total supply amount of the monomer by the reference time, the average supply rate is a period from 0% to k% (k is 0 to 20) of the reference time. A high-speed supply period of the monomer that supplies the monomers α _{1 to} α _n at a speed higher than Vk;
The value of the weight average molecular weight of the polymer in the reactor at 30 minutes, 1 hour, and 2 hours after the start of dropping of the polymerization initiator is the weight of the polymer (P) at the end of the reaction. To be 80-120% of the average molecular weight,
During the high-speed supply period of the polymerization initiator, 30 to 90% by mass of the total supply amount of the polymerization initiator is supplied into the reactor, and all of the monomer is supplied during the high-speed supply period of the monomer. The manufacturing method of the polymer which supplies 2-50 mass% of supply_amount | feed_rate in the said reactor.   The polymerization initiator is dropped at a constant rate after the end of the high-speed supply period of the polymerization initiator, and the monomer is dropped at a constant rate after the end of the high-speed supply period of the monomer. A method for producing the polymer according to 1.   The method for producing a polymer according to claim 1 or 2, wherein the polymer (P) is a polymer for lithography. A resist comprising a step of producing a polymer for lithography by the production method according to claim 3 and a step of mixing the obtained polymer for lithography, a resist solvent, and a compound that generates an acid upon irradiation with actinic rays or radiation. A method for producing the composition. A step of producing a resist composition by the production method according to claim 4 , a step of applying the obtained resist composition on a work surface of a substrate to form a resist film, and the resist film, A method for producing a substrate on which a pattern is formed, comprising a step of exposing and a step of developing the exposed resist film using a developer.

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