JP2013221125A - Method for producing polymer, method for producing resist composition, and method for producing substrate with pattern formed thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polymer, by which variation among lots of the polymer can be further reduced.SOLUTION: In a method for producing a polymer, a polymerization rate is measured in every hour from a time when the polymerization reaction is started. When a polymerization rate is less than 90 mol% in n hours (n is an integer of 1 or more) and a polymerization rate is equal to or more than 90 mol% in (n+1) hours, the value of a standard deviation Z of the weight average molecular weight xof the polymer which is produced in each period from (t-1) hours to t hours (where t is an integer of 1 to n) after the polymerization reaction is started, is 10% or less of the weight average molecular weight y at the end of the polymerization reaction. Further, the proportion of the total mass of monomers supplied to a reaction vessel with respect to the mass of a reaction liquid in the reaction vessel at the end of the polymerization reaction is 40 mass% or less.

Description

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

In recent years, a resist pattern formed in a manufacturing process of a semiconductor element, a liquid crystal element, or the like has been rapidly miniaturized due to advances in semiconductor lithography technology. As a technique for miniaturization, there is a reduction in wavelength of irradiation light. Specifically, the irradiation light has become shorter from conventional ultraviolet rays typified by g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm) to shorter wavelength DUV (Deep Ultra Violet). .
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. . Furthermore, these immersion lithography techniques are also being studied. Also, as a different type of lithography technology, electron beam lithography technology has been energetically studied.

A “chemically amplified resist composition” containing a photoacid generator has been proposed as a highly sensitive resist composition used for forming a resist pattern using the irradiation light or electron beam of the short wavelength. Improvement and development of the amplified resist composition are underway.
For example, as a chemically amplified resist polymer used in ArF excimer laser lithography, an acrylic polymer that is transparent with respect to light having a wavelength of 193 nm has attracted attention. As the acrylic polymer, for example, a polymer of (meth) acrylic acid ester having an adamantane skeleton in an ester portion and (meth) acrylic acid ester having a lactone skeleton in an ester portion has been proposed (Patent Document 1). etc).

With the miniaturization of resist patterns, demands for quality of polymers for semiconductor lithography have become stricter. For example, a lot variation in manufacturing a polymer for semiconductor lithography may cause a minute defect during development, which may cause a defect in device design.
Patent Document 2 listed below describes a method of synthesizing a resin having an acid-dissociable group using a living radical polymerization initiator as a method for reducing fluctuations in molecular weight distribution due to lot differences.

JP 10-319595 A JP 2009-175746 A

However, in the method described in Patent Document 2, it is necessary to use a specific polymerization initiator, and it is also necessary to optimize the manufacturing conditions accompanying the change of the polymerization initiator.
In recent years, demands for reducing variations in lots of resist polymers have become increasingly severe, and conventional methods are not necessarily sufficient.
The present invention has been made in view of the above circumstances, and a method for producing a polymer capable of further reducing variation between polymer lots, a method for producing a resist composition using the production method, and the resist composition An object of the present invention is to provide a method for manufacturing a substrate on which a pattern is formed, using the method for manufacturing an object.

  The inventors of the present invention have found that the variation in molecular weight between lots over time can be reduced by suppressing the variation in the molecular weight of the polymer produced at each time during the polymerization reaction.

The method for producing a polymer of the present invention comprises a polymerization step in which two or more monomers are subjected to a radical polymerization reaction using a polymerization initiator in the presence of a solvent in a reaction vessel, and the polymerization reaction is stopped. A reaction stopping step
The polymerization rate is measured every hour after the start of the polymerization reaction, the polymerization rate is less than 90 mol% after n hours (n is an integer of 1 or more), and the polymerization rate after (n + 1) hours is 90 mol%. When it becomes more than
The value of the standard deviation Z of the weight-average molecular weight x _t of polymer produced respectively between the polymerization reaction started (t-1) times after ~t time after (t is an integer of 1 to n) is polymerized Is 10% or less of the weight average molecular weight y at the end of the reaction, and the total mass of monomers supplied to the reaction vessel with respect to the mass of the reaction liquid in the reaction vessel at the end of the polymerization reaction. The manufacturing method of the polymer whose ratio is 40 mass% or less.

In the polymerization reaction period from the start of the polymerization reaction to the start of the operation for stopping the polymerization reaction, a monomer supply step for supplying the monomer continuously or dropwise into the reaction vessel ,
It is preferable to supply the monomer over 70% or more of the polymerization reaction period.

The present invention includes a step of producing a resist polymer by the production method of the present invention, and a step of mixing the obtained resist polymer and a compound that generates an acid upon irradiation with actinic rays or radiation. A method for manufacturing a product is provided.
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, and the resist film And a method for producing a substrate on which a pattern is formed, which comprises a step of exposing and a step of developing the exposed resist film using a developer.

According to the present invention, a polymer having a small lot-to-lot variation can be obtained.
A resist composition using a polymer obtained by the method for producing a polymer of the present invention is excellent in stability of performance because the lot-to-lot variation of the polymer is small.
According to the substrate manufacturing method of the present invention, a highly accurate fine pattern can be stably formed.

It is an explanatory view of a method of obtaining the weight average molecular weight x _t according to the present invention. It is an explanatory view of a method of obtaining the weight average molecular weight x _t according to the present invention.

In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acryloyloxy” means acryloyloxy or methacryloyloxy.
<Polymer>
The polymer of the present invention is not particularly limited, but is preferably a polymer for semiconductor lithography in which lot-to-lot variation tends to be a problem. Further, among the polymers for semiconductor lithography, it is particularly preferable to be a resist polymer that has a strict demand for reduction in lot-to-lot variation.
The polymer for semiconductor lithography preferably has a structural unit (a) having a polar group, and the resist polymer has a structural unit (b) having an acid leaving group in addition to the structural unit (a). It is preferable to have.
The weight average molecular weight of the polymer for semiconductor lithography is not particularly limited, but generally 1,000 to 100,000 is preferable, and 3,000 to 50,000 is more preferable.

[Structural unit (a)]
The polymer in the present invention preferably has a structural unit (a) 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 polymer used in the resist composition in the pattern forming method of exposing with 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, and further described below. It is preferable to have a structural unit having a hydrophilic 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 carbon ring or a heterocyclic ring may be condensed with the lactone ring.
In the case where the polymer contains a structural unit having a lactone skeleton, the content thereof is preferably 20 mol% or more, more preferably 25 mol% or more of all structural units (100 mol%) from the viewpoint of adhesion to a substrate or the like. 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 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]} cited decan-3-one and the like . Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
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, hydroxy group, cyano group, methoxy group, carboxy group, and amino group.
Among these, it is preferable that the polymer used for the resist composition in the pattern formation method exposed with 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 polymer is preferably from 5 to 30 mol%, more preferably from 10 to 25 mol%, of the total structural units (100 mol%) from the viewpoint of the resist pattern rectangularity. .

  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 adhesiveness 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.
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.

[Structural unit (b)]
The polymer preferably has a structural unit (b) having an acid-eliminable group in addition to the above-mentioned structural unit (a) having a polar group when used for resist applications. You may have the structural unit.
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 formation of a resist pattern.
The proportion of the structural unit having an acid leaving group is preferably 20 mol% or more, more preferably 25 mol% or more, 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 a 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 hydrocarbon 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. (Represents a tertiary hydrocarbon group, a tetrahydrofuranyl group, a tetrahydropyranyl group, or an oxepanyl group.) (Meth) acrylic acid ester bonded directly or through a linking group.

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.
As the monomer having an acid leaving group, one type may be used alone, or two or more types may be used in combination.

<Method for producing polymer>
A preferred embodiment of the method for producing a polymer of the present invention will be described.
In the method for producing a polymer of the present embodiment, a solvent (hereinafter also referred to as a polymerization solvent), a monomer, and a polymerization initiator are supplied into a reaction vessel, and the solution (reaction solution) in the reaction vessel is supplied. A polymerization step of polymerizing the monomer, and a reaction stopping step of stopping the polymerization reaction.
In the present invention, the period from the start of the polymerization reaction to the start of the operation for stopping the polymerization reaction (stopping operation) is referred to as the polymerization reaction period.
The polymerization step in the present embodiment is a solution polymerization method in which a monomer is radically polymerized using a polymerization initiator in the presence of a polymerization solvent.

  In the solution polymerization method, the monomer and the polymerization initiator may be supplied to the reaction vessel either continuously or dropwise. From the point that dispersion of average molecular weight, molecular weight distribution, etc. due to differences in production lots is small and a polymer having good reproducibility is easily obtained, a dropping solution containing a monomer and a polymerization initiator is dropped into a reaction vessel. Legal is preferred.

Examples of the polymerization solvent include the following.
Ethers: chain ether (diethyl ether, propylene glycol monomethyl ether (hereinafter referred to as “PGME”), etc.), cyclic ether (tetrahydrofuran (hereinafter referred to as “THF”), 1,4-dioxane, etc. )etc.
Esters: methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”), γ-butyrolactone, and the like.
Ketones: acetone, methyl ethyl ketone (hereinafter referred to as “MEK”), methyl isobutyl ketone (hereinafter referred to as “MIBK”), 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.

  As the polymerization initiator, those that generate radicals efficiently by heat are preferable. Examples of the polymerization initiator include azo compounds (2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis [2- (2-imidazoline). -2-yl) propane], etc.), organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc. Etc.).

In the production method of the present embodiment, at least a part of the polymerization solvent and / or at least a part of the monomer can be charged in the reaction vessel in advance.
It is preferable that a part of the polymerization solvent is put in the reaction vessel in advance, and the rest is supplied into the reaction vessel as a solvent for the dropping solution.
When the monomers are charged in the reaction vessel in advance, it is preferable that a part of the total monomers used for the polymerization reaction is put in the reaction vessel, and the rest is added to the dropping solution and supplied into the reaction vessel. .
In the reaction vessel, only the polymerization solvent may be placed in advance, or only the monomer may be placed, or a mixture thereof may be placed.

The polymerization reaction is performed by heating a liquid (polymerization solvent and / or monomer) previously charged in a reaction vessel to a predetermined polymerization temperature and supplying a polymerization initiator in the presence of the monomer. Is started.
The polymerization reaction period is from the time when the polymerization initiator is supplied into the reaction vessel to the time when the end operation of the polymerization reaction is started. The completion of the polymerization reaction means an operation that stops the radical polymerization reaction or causes a decrease in the growth reaction rate, specifically, an operation that lowers the temperature in the reaction vessel, or a radical reaction such as a polymerization inhibitor or oxygen. An operation for supplying the inhibitor into the reaction vessel can be mentioned.

In the dropping polymerization method, the monomer may be dropped only with the monomer or may be dropped as a monomer solution in which the monomer is dissolved in the polymerization solvent.
The polymerization initiator may be dropped directly after being dissolved in the monomer, may be dropped after being dissolved in the monomer solution, or may be dropped after being dissolved only in the polymerization solvent.
After the monomer and the polymerization initiator are mixed in the same storage tank, they may be dropped into the reaction vessel; they may be dropped from the independent storage tank into the reaction vessel; respectively, from the independent storage tank to the reaction vessel. They may be mixed immediately before feeding and dropped into the reaction vessel.
One of the monomer and the polymerization initiator may be dropped first, and then the other may be dropped with a delay, or both may be dropped at the same timing.
The dropping speed may be constant until the dropping is completed, or may be changed in multiple stages according to the consumption speed of the monomer or the polymerization initiator.
The dripping may be performed continuously or intermittently.

[Monomer supply process]
The start time of the monomer supply step is the time when the monomer is first supplied into the reaction vessel after the start time of the polymerization reaction period. The end point of the monomer supply step is the time point when all the monomers used for the polymerization reaction have been supplied into the reaction vessel.
In the polymerization reaction period, it is preferable to start the monomer supply at the same time as the supply of the polymerization initiator into the reaction vessel is started.
The polymerization reaction may be stopped immediately after supplying all the monomers in the reaction vessel, but after supplying all the monomers in the reaction vessel, the reaction solution in the reaction vessel is set in advance by polymerization. It is preferable to carry out an aging step in which the polymerization reaction proceeds while maintaining the temperature.

The monomer is preferably supplied to the reaction vessel by the following method (i) or (ii).
(I) A first solution containing a monomer in a first composition is charged in a reaction vessel in advance, the reaction vessel is heated to a predetermined polymerization temperature, and then the monomer is placed in the reaction vessel. A method in which a second solution containing a target composition is added dropwise.
The target composition means the composition of monomer units (unit: mol%) in the polymer to be obtained.
In the first composition of the first solution charged in the reaction vessel in advance, the composition ratio (molar component) of the monomer having a relatively slow consumption rate is determined according to the consumption rate of each monomer by the polymerization reaction. Ratio) is preferably larger than the molar fraction in the target composition. According to this method, variations in the monomer composition and chain structure in the polymer produced particularly in the early stage of polymerization are likely to be reduced.
In this specification, the process of dripping the 2nd solution containing a monomer with a target composition is called a main process.

(Ii) The first solution containing the monomer in the first composition is charged in the reaction vessel in advance, the reaction vessel is heated to a predetermined polymerization temperature, The second solution containing the body in the target composition is dropped (main process), and after the dropping of the second solution is completed, one or more of the third solutions containing the monomer in the third composition are added. A method of dropping (referred to as post-process).
In the third composition of the third solution dropped after the main step, the composition ratio (molar fraction) of the monomers having a relatively slow consumption rate according to the consumption rate by the polymerization reaction of each monomer. Is preferably smaller than the molar fraction in the target composition (may be zero).
In this method, it is necessary that the polymerization initiator is present in the reaction vessel when the third solution is dropped into the reaction vessel. Accordingly, it is preferable to supply the polymerization initiator into the reaction vessel also in the subsequent step.
According to this method, the dispersion | variation in the monomer composition and chain structure in the polymer produced | generated especially at the early stage of polymerization and a late stage is easy to be reduced.

  In the present invention, the monomer supply period from the start to the end of the monomer supply step is preferably 70% or more of the polymerization reaction period. By supplying the monomer over 70% or more of the polymerization reaction period, the lot-to-lot variation in the molecular weight of the resulting polymer can be effectively suppressed. The monomer supply period is more preferably 75% or more, and more preferably 80% or more of the polymerization reaction period, in that molecular weight variation among the lots is more easily suppressed. The ratio of the monomer supply period to the polymerization reaction period may be 100%, but is preferably 95% or less, more preferably 90% or less in that the monomer reaction rate increases and good productivity is easily obtained. preferable.

In the present invention, the total mass of monomers supplied into the reaction vessel is 40% by mass or less with respect to the mass of the reaction solution in the reaction vessel at the end of the polymerization reaction period. Specifically, of all the raw materials (including at least the polymerization solvent, the monomer, and the polymerization initiator) supplied to the reaction vessel, the polymerization solvent is adjusted so that the total amount of monomers is 40% by mass or less. Set usage.
When the ratio of the total amount of monomers supplied to the reaction liquid with respect to the reaction liquid at the end of the polymerization reaction period is 40% by mass or less, a rapid change in the polymerization system is suppressed and the molecular weight is constant. Since coalescence is easily generated stably over a long period of time, variation in molecular weight between lots tends to be small. The total proportion of the monomers is preferably 30% by mass or less, and more preferably 25% by mass or less. The lower limit of the total ratio of the monomers is not particularly limited, but is preferably 5% by mass or more, and more preferably 10% by mass or more in terms of production efficiency.
In addition, during the polymerization reaction period, the total mass of the monomers supplied to the reaction vessel up to that time does not exceed 40% by mass (40% by mass or less) with respect to the mass of the reaction solution in the reaction vessel. Is preferred.
In the method (ii), the main step of dropping the second solution containing the monomer in the target composition is preferably 40 to 100%, more preferably 50 to 90% of the monomer supply period.

In the method (i) or (ii), the monomer content in the liquid supplied in advance into the reaction vessel before the start of the polymerization reaction is preferably 2 to 16% by mass, and 3 to 15.5% by mass. More preferably, 4-15 mass% is further more preferable. Within this range, the polymerization heat generation at the initial stage of polymerization is not large, and the difference between the molecular weight of the polymer produced at the initial stage of polymerization and the weight average molecular weight at the end of the polymerization reaction can be reduced.
15-50 mass% is preferable, as for the monomer content in the sum total of the liquid supplied to reaction container after a polymerization reaction start, 20-45 mass% is more preferable, and 25-40 mass% is more preferable. Within this range, the balance between the polymerization heat generated during the supply of the monomer solution and the cooling due to the supply of the monomer solution is good, and the temperature control is easy.

[Polymerization initiator supply rate]
The period for supplying the polymerization initiator into the reaction vessel may be from the start of the polymerization reaction to the end of the monomer supply period, or the supply of the polymerization initiator may be ended before the end of the monomer supply period. It is preferable to supply the polymerization initiator until the end of the monomer supply period.

The supply rate of the polymerization initiator may be constant or may change over time. When the initiator supply rate is controlled so that the change with time of the molar concentration ratio of radicals generated from the initiator in the reaction vessel to the monomer molar concentration in the reaction vessel becomes smaller from the initial stage of polymerization to the latter stage, From the latter stage, the variation with time of the molecular weight of the polymer produced at each moment becomes smaller, which is preferable.
For example, when the monomer is supplied to the reaction vessel by the above method (i) or (ii), the period from the start of dropping of the polymerization initiator to the end of the main step (sometimes referred to as a reference time). 15 to 90% of the total amount of polymerization initiator used in the main process is supplied in the initial stage before 3 to 20% elapses, and then the polymerization initiator is supplied at a lower speed than the initial stage. It is preferable to do.
The initial stage is preferably 4 to 17.5% of the reference time, and more preferably 5 to 15%. The supply amount of the polymerization initiator in the initial stage is more preferably 17.5 to 70% by mass, and further preferably 20 to 65% by mass, based on the total supply amount of the polymerization initiator used in the main process.

[Deviation value Z of weight average molecular weight]
In the present invention, the standard deviation Z of the weight-average molecular weight x _t of polymer produced respectively between the polymerization reaction started (t-1) times after ~t time after (t is an integer of 1 to n) is The weight average molecular weight y at the end of the polymerization reaction is 10% or less.
The weight average molecular weight y is obtained by sampling the reaction solution in the reaction vessel after stopping the reaction, measuring the molecular weight of the polymer in the sample by gel permeation chromatography (GPC), and converting it to polystyrene.
The standard deviation Z is a value obtained by the following formula (1).

In the present invention, the polymerization rate (unit: mol%) refers to the molar fraction of monomers consumed by polymerization relative to the total amount of monomers used in the polymerization reaction.
The amount of monomer consumed by polymerization is determined by measuring the difference between the amount of monomer supplied into the reaction vessel by the time of measurement and the unreacted monomer remaining in the reaction solution at the time of measurement. can get.
That is, the reaction solution is sampled from the reaction vessel, the content of unreacted monomer is measured for each monomer by high performance liquid chromatography, and the total value of these is obtained. By subtracting the total amount of remaining monomers from the total amount of monomers supplied up to the time of measurement, the amount of monomer consumed by polymerization up to the time of measurement can be obtained. Using this value, the total amount of monomers used in the polymerization reaction, that is, the amount of monomers consumed by the polymerization by the time of measurement relative to the total amount of monomers supplied to the reaction vessel by the end of the polymerization reaction The ratio (mol%) is determined as the polymerization rate at the time of the measurement.

In the formula (1), n is the time from the start of the polymerization reaction until the polymerization rate (mol%) reaches 90 mol%, and is an integer of 1 or more. That is, the polymerization rate is measured every hour after the start of the polymerization reaction, the polymerization rate is less than 90 mol% after n hours (n is an integer of 1 or more), and the polymerization rate after (n + 1) hours is 90%. Find n when it is at least mol%. n is not greater than the number of hours of the polymerization reaction period. For example, when the polymerization reaction period is 7 hours, n is 7 or less.
Specifically, immediately after the start of the polymerization reaction is set to 0 hour, and thereafter, the reaction solution is sampled and measured every hour. In this specification, the term “immediately after the start of the polymerization reaction” means 0 to 60 seconds after the start of the supply of the polymerization initiator.

In the formula (1), the weight average molecular weight x _t is the weight generated in 1 hour from (t-1) hours to t hours (t is an integer of 1 to n) after the polymerization reaction starts. It is the weight average molecular weight (x ₁ , x ₂ , x ₃ ... X _n ) of the coalescence. In the formula (1), x _a is an average value of x _{1 to} x _n . The weight average molecular weight _xt is determined by the following method.

(Determination of weight average molecular weight _{x t)}
The reaction solution in the reaction vessel is sampled every hour from the start of the polymerization reaction, and the molecular weight of the polymer in the sample is measured by gel permeation chromatography (GPC). Thereby, the elution curve by GPC at the time of each measurement is obtained. Since the elution curve is obtained as a function of elution time and signal intensity (correlates with the weight-based abundance), a standard polystyrene calibration curve I is used to determine the molecular weight and the weight-based abundance (signal) of the polymer. It is converted into a curve (function F with respect to the molecular weight of polymer weight) representing the relationship with (strength). At this time, normalization is performed so that the area surrounded by the curve representing the function F and the base line B is 1.
FIG. 1 is an example of the function F. The function F means a curve represented in a range from a peak start (indicated by a symbol Ps in the figure) to a peak end (indicated by a symbol Pe in the figure) in FIG. That is, the base line B is drawn on the elution curve converted by the calibration curve I (for example, FIG. 1), the intersection point between the curve B representing the function F on the low molecular weight side and the base line B is Ps, and the high molecular weight side Let Pe be the intersection of the curve representing the function F and the baseline.
Functions F and polymerization rate C of each function F _t after t time from the initiation of _{polymerization,} when the polymerization rate C _t, for the polymer formed during the 1 hour until after t time later (t-1) time The function F is given by F _t × C _t −F _t−1 × C _t−1 . Thus obtained, using a function F of the formed polymer during one hour from the time of each measurement until the next measurement to determine the weight average molecular weight x _t of polymer produced during the 1 hour.
For example, the function F and the polymerization rate C after 1 hour and 2 hours from the start of polymerization are defined as functions F ₁ , F ₂ , polymerization rate C ₁ , and C ₂ , respectively. For example, as shown in FIG. 2, when C ₁ = 20 mol% and C ₂ = 40 mol%, the molecular weight of the polymer weight of the polymer produced during 1 hour from 1 hour to 2 hours later Is obtained as a difference (F = f2−f1) between F ₁ × C ₁ (represented by the symbol f1 in the figure) and F ₂ × C ₂ (represented by the symbol f2 in the diagram). The more function F (= f2-f1), the weight average molecular weight x ₂ of formed polymer during one hour after 1 hour to 2 hours after is obtained.

In this way, the weight average molecular weights x ₁ , x ₂ ,..., X _n for each hour until n hours immediately before the polymerization rate (mol%) reaches 90 mol% are obtained, and the above formula (1) is obtained. The value of these standard deviations Z is obtained.
The standard deviation Z is a value reflecting the degree of variation in average molecular weight from the start of the polymerization reaction to the measurement time (n) immediately before the polymerization rate reaches 90%.
When the value of the standard deviation Z is 10% or less of the weight average molecular weight y at the end of the polymerization reaction, the variation over time in the molecular weight of the polymer produced at each moment during the polymerization reaction is favorably reduced.
In addition, when the value of the standard deviation Z is 10% or less of the weight average molecular weight y at the end of the polymerization reaction, the variation in molecular weight between lots when a desired polymer is repeatedly produced under the same production conditions is good. Reduced.

Therefore, in the method for producing a polymer in which a target polymer is repeatedly produced under the same production conditions, in determining the production conditions, the polymer is produced under the production conditions W, and the standard deviation represented by the above formula (1) The suitability of the production condition W can be evaluated by measuring Z and the weight average molecular weight y at the end of the polymerization reaction, and whether the value of the standard deviation Z is 10% or less of the weight average molecular weight y. When the value of the standard deviation Z is 10% or less of the weight average molecular weight y, the production condition W was able to satisfactorily suppress the variation in molecular weight between lots when the desired polymer was repeatedly produced under the same production conditions. In order to obtain a polymer, it can employ | adopt as an appropriate manufacturing condition.
When the standard deviation Z exceeds 10% of the weight average molecular weight y, the production conditions are changed and the polymer is produced again. Whether the value of the standard deviation Z is 10% or less of the weight average molecular weight y. The suitability of the manufacturing conditions is evaluated. The production conditions to be changed at this time are an initiator supply method, a monomer supply method, a ratio of the total amount of monomers supplied to the reaction liquid with respect to the reaction liquid at the end of the polymerization reaction period, or a combination thereof. Is preferred.
For example, a method for supplying a polymerization initiator, in which the monomer supply time is lengthened, is to supply a part of the total supply amount of the polymerization initiator used in the main process in the initial stage of polymerization, and then from the initial stage. By changing the method to supply the polymerization initiator at a low speed, reducing the total ratio of the monomers supplied to the reaction solution relative to the reaction solution at the end of the polymerization reaction period, or combining them, The ratio of Z to y can be reduced.

  Thus, it is preferable to predetermine production conditions satisfying “standard deviation Z is 10% or less of weight average molecular weight y”, and to repeatedly produce the desired polymer under the same production conditions. When the polymer is produced under the same conditions as the production conditions determined in advance, the operation for obtaining the standard deviation Z need not be performed. By using such production conditions, as shown in Examples described later, production reproducibility is improved, and a polymer having a very small difference in average molecular weight between lots can be produced repeatedly.

In the polymerization step, a predetermined amount of a monomer and a polymerization initiator are supplied, and after a polymerization reaction is performed for a predetermined time, a reaction stopping operation is performed to stop the polymerization reaction to obtain a polymer solution.
The obtained polymer solution is purified as necessary. For example, after diluting to a suitable solution viscosity with a diluting solvent such as 1,4-dioxane, acetone, THF, MEK, MIBK, γ-butyrolactone, PGMEA, PGME, ethyl lactate, etc., methanol, ethanol, isopropyl alcohol, water, hexane In a poor solvent such as heptane, diisopropyl ether, or a mixed solvent thereof, the polymer is precipitated. This process is called a reprecipitation process, and is very effective for removing unreacted monomers, polymerization initiators and the like remaining in the polymer solution. If the unreacted monomer remains as it is, the sensitivity decreases when used as a resist composition, so it is preferable to remove it as much as possible. The monomer content as an impurity in the polymer is more preferably 2.0% by mass or less, further preferably 1.0% by mass or less, particularly preferably 0.29% by mass or less, and 0.25% by mass or less. Most preferred.

As the poor solvent, any solvent may be used as long as the polymer to be produced is not dissolved, and any known solvent can be used, but unreacted monomers, polymerization initiators and the like used in the polymer for semiconductor lithography can be used. In view of efficient removal, methanol, isopropyl alcohol, diisopropyl ether, heptane, water, or a mixed solvent thereof is preferable.
Since the amount of the poor solvent used can further reduce the remaining unreacted monomer, it can be used in the same mass or more as the polymer solution, preferably 3 times or more, more preferably 4 times or more, and further more preferably 5 times or more. Preferably, 6 times or more is particularly preferable.

Thereafter, the precipitate is filtered off to obtain a wet powder.
Further, after the wet powder is dispersed again in a poor solvent to obtain a polymer dispersion, an operation of filtering the polymer can be repeated. This step is called a restructuring step and is very effective for further reducing unreacted monomers, polymerization initiators and the like remaining in the polymer wet powder.
It is preferable to purify the polymer only by the reprecipitation step without performing the restructuring step in that the polymer can be obtained while maintaining high productivity.

The obtained wet powder can be sufficiently dried to obtain a dry powder polymer.
In addition, after filtering off, it may be used as a lithographic composition by dissolving it in a suitable solvent without drying and using it as a lithographic composition. Also good. At that time, additives such as a storage stabilizer may be appropriately added.
Further, after drying, it may be dissolved in a suitable solvent and further concentrated to remove the low boiling point compound, and then used as a composition for lithography. At that time, additives such as a storage stabilizer may be appropriately added.

<Method for producing resist composition>
The method for producing a resist composition of the present invention comprises producing a resist polymer by the production method of the present invention, and the resulting resist polymer and a compound that generates an acid upon irradiation with actinic rays or radiation (hereinafter referred to as “ This is a method for producing a resist composition having a step of mixing a photoacid generator ”. Preferably, the polymer and the photoacid generator are dissolved in a resist solvent to produce a resist composition.
When the resist polymer is produced, as the monomer, the monomer that leads the structural unit (a) described above (monomer having a polar group) and the monomer that leads the structural unit (b) described above ( It is preferable to use a monomer having an acid leaving group. The obtained resist composition includes a resist polymer obtained by the production method of the present invention, and a compound that generates an acid upon irradiation with actinic rays or radiation. Is a chemically amplified resist composition.

[Resist solvent]
Examples of the resist solvent include the same solvents as the polymerization solvent.
[Compound that generates acid upon irradiation with actinic ray or radiation (photoacid generator)]
As the photoacid generator, known photoacid generators for the chemically amplified resist composition can be appropriately selected and used. 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, and the resist film is irradiated with light, then baked (PEB), and then left for several hours before the next development process. Although it is a line, the occurrence of the deterioration of the cross-sectional shape of the resist pattern is further suppressed when left as such (timed).

The nitrogen-containing compound is preferably an amine, more preferably a secondary lower aliphatic amine or a tertiary lower aliphatic amine.
As for the quantity of a nitrogen-containing compound, 0.01-2 mass parts is preferable with respect to 100 mass parts of polymers.

[Organic carboxylic acid, phosphorus oxo acid or derivative thereof]
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 amount of the acid compound is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the polymer.

[Additive]
The resist composition may contain various additives such as a surfactant, 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 fine pattern is formed>
The method for producing a substrate on which a fine pattern is formed according to the present invention comprises a step of producing a resist composition by the production method of the present invention, and applying the obtained resist composition onto a work surface of the substrate to form a resist. A step of forming a film, a step of exposing the resist film, and a step of developing the exposed resist film using a developer.
Hereinafter, an example of the manufacturing method of the substrate will be described.

  First, a resist composition is applied by spin coating or the like to the surface (processed surface) of a substrate to be processed 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 to-be-processed board | substrate with which this resist composition was apply | coated by baking process (prebaking) etc.

Next, the resist film is irradiated with light having a wavelength of 250 nm or less through a photomask to form a latent image (exposure). As irradiation light, a KrF excimer laser, an ArF excimer laser, an F ₂ excimer laser, and an EUV excimer laser are preferable, and an 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 the 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). A well-known thing can be used as an alkali developing solution.
After development, the substrate is appropriately rinsed with pure water or the like. In this way, a resist pattern is formed on the substrate to be processed.

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 pattern is formed.

According to the production method of the present invention, variations in the average molecular weight of the polymer produced over time in the polymer polymerization step are reduced. In addition, production reproducibility when a polymer is repeatedly produced under the same conditions is improved, and a polymer in which variation in molecular weight among lots is suppressed to a small level at a high level that has not been conventionally obtained can be obtained.
The resist composition obtained by the present invention is excellent in stability of resist performance such as sensitivity and development contrast since the molecular weight variation of the polymer for semiconductor lithography contained in the resist composition is small.
Therefore, according to the manufacturing method of the board | substrate of this invention, a highly accurate fine resist pattern can be formed stably by using the resist composition concerning this invention. In addition, it is also suitable for pattern formation by photolithography using exposure light having a wavelength of 250 nm or less or lithography using electron beam lithography, for example, ArF excimer laser (193 nm), which requires use of a highly sensitive resist composition. be able to.

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

<Measurement method of 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 a reaction solution): a solution obtained by dissolving about 30 mg of a sampled reaction solution in 5 mL of THF and filtering 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).

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

  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% / 1
Up to 00% by volume.
Measurement time: 36.5 to 44 minutes: Liquid A / liquid B = 0 volume% / 100 volume%.

<Evaluation of sensitivity of resist composition>
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.
A curve plotting the logarithm of the exposure amount (mJ / cm ² ) and the residual film thickness ratio (hereinafter referred to as the residual film ratio) (%) when developed for 60 seconds with respect to the initial film thickness, based on the obtained data. (Hereinafter, exposure amount-residual film rate curve) was prepared, and Eth sensitivity (required exposure amount for setting the residual film rate to 0%, which represents sensitivity) was determined as follows.
Eth sensitivity: exposure amount (mJ / cm ² ) at which the exposure amount-residual film rate curve intersects with a residual film rate of 0%
The value of Eth represents sensitivity, and the smaller the value, the higher the sensitivity.

<Lot difference in weight average molecular weight>
In each example, the polymer was synthesized five times under the same conditions, and the weight average molecular weight of each polymer obtained was measured. The standard deviation of the number of measurements 5 was determined and used as the difference between the lots in the weight average molecular weight. The smaller the difference between lots, the better the reproducibility of the polymerization reaction, and the smaller the lot-to-lot variation in the weight average molecular weight.

  The monomer used in the following examples is a monomer (m-1) represented by the following formula (m-1), a monomer (m-2) represented by the following formula (m-2), And a monomer (m-3) represented by the following formula (m-3).

<Example 1>
The following mixture S1 was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer 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, the following mixture T1 and the polymerization initiator solution were simultaneously fed from separate dropping funnels, and T1 was dropped into the flask over 4 hours and the polymerization initiator solution over 20 minutes. Furthermore, 80% by mass (U1) of the following mixture U is added dropwise over 1 hour from the end of the supply of T1, and the remaining 20% by mass (U2) is added dropwise over 1 hour. Hold for 1 hour (aging process). The reaction solution was sampled every hour from the start of dropping of T1, and cooled to room temperature after 7 hours to stop the reaction.
From the sampled reaction solution, the Mw (x _t ) of the polymer produced during 1 hour after (t-1) time to t time in the polymerization reaction step, and Mw ( y), the polymerization rate, the measurement time (n) immediately before the polymerization rate reaches 90%, the standard deviation (Z) represented by the above formula (1), and the ratio of Z to y were determined. (The same applies hereinafter).
The total of the dropping time and the aging time is the polymerization reaction period, and the dropping time is the monomer supply period. From these values, the ratio of the monomer supply period during the polymerization reaction period was determined. The results are shown in Table 1 (hereinafter the same).
The mass of the reaction liquid at the end of the polymerization reaction period is the mass of the liquid (polymerization solvent and monomer in this example) charged in advance in the reaction vessel, and the monomer, polymerization initiator, and polymerization solvent supplied dropwise. Was calculated as a total value, and the ratio of the total amount of monomers supplied to the mass of the reaction solution was calculated. The results are shown in Table 1 (hereinafter the same).

(S1)
3.99 parts (31.3 mol%) of monomer m-1
7.68 parts (52.4 mol%) of monomer m-2,
2.88 parts (16.3 mol%) of monomer m-3,
99.3 parts ethyl lactate.
(T1)
24.03 parts (40 mol%) of monomer m-1;
27.71 parts (40 mol%) of monomer m-2,
16.68 parts (20 mol%) of monomer m-3,
101.8 parts ethyl lactate,
0.690 parts of dimethyl-2,2′-azobisisobutyrate (0.7 mol% based on the total amount of monomers in S1 and T1).
(Polymerization initiator solution)
2.0 parts ethyl lactate,
1.280 parts of dimethyl-2,2′-azobisisobutyrate (1.3 mol% based on the total amount of monomers in S1 and T1).
(U)
1.09 parts (67.6 mol%) of monomer m-1;
0.73 part (32.4 mol%) of monomer m-3,
34.5 parts ethyl lactate,
0.054 parts dimethyl-2,2′-azobisisobutyrate (2.5 mol% with respect to the total amount of monomers in U).

[Purification of polymer]
After 7 hours of reaction time, the reaction was stopped by cooling to room temperature, and the polymer 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 separated by filtration 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. Mw was calculated | required about the obtained polymer P1. The results are shown in Table 2 (hereinafter the same).
[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 2 (hereinafter the same).

[Difference in weight average molecular weight between lots]
A polymer was further synthesized four times under the same conditions as in this example (Production 1-1) (Production 1-2 to 1-5). However, the measurement of each item shown in Table 1 was not performed. The weight average molecular weight (Mw) of the polymer obtained each time was measured. The standard deviation of the number of measurements 5 was determined and used as the difference between the lots in the weight average molecular weight. The results are shown in Table 2 (hereinafter the same). The smaller the difference between lots, the better the reproducibility of the polymerization reaction, and the smaller the lot-to-lot variation in the weight average molecular weight.
A resist composition was prepared under the same conditions using the polymers obtained each time, and the sensitivity (Eth) was evaluated. The results are shown in Table 2 (hereinafter the same).

<Example 2>
The following mixture S1 was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer 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, the following mixture T1 and the polymerization initiator solution were simultaneously fed from separate dropping funnels, and T1 was dropped into the flask over 6 hours and the polymerization initiator solution over 20 minutes. Further, the temperature of 80 ° C. was maintained for 1 hour immediately after the end of the supply of T1 (aging process). The polymerization reaction solution was sampled every hour from the start of dropping of T1, and after 7 hours, the reaction was stopped by cooling to room temperature. The value of the item shown in Table 1 was calculated | required from the sampled reaction liquid.

(S1)
6.53 parts (31.3 mol%) of monomer m-1;
11.76 parts (52.4 mol%) of monomer m-2,
4.84 parts (16.3 mol%) of monomer m-3,
170.4 parts of ethyl lactate,
139.4 parts of PGMEA.
(T1)
Monomer m-1 73.44 parts (40 mol%),
84.67 parts (40 mol%) of monomer m-2,
50.98 parts (20 mol%) of monomer m-3,
232.4 parts of ethyl lactate,
199.7 parts of PGMEA,
4.633 parts of dimethyl-2,2′-azobisisobutyrate (0.7 mol% based on the total amount of monomers in S1 and T1).
(Polymerization initiator solution)
11.7 parts ethyl lactate,
1.158 parts of dimethyl-2,2′-azobisisobutyrate (1.3 mol% based on the total amount of monomers in S1 and T1).
[Purification of polymer]
The evaluation results obtained by purifying and evaluating the polymer in the same manner as in Example 1 are shown in Table 2.

<Example 3>
The following mixture S1 was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer 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, the following mixture T1 and the polymerization initiator solution were simultaneously fed from a separate dropping funnel, and T1 was dropped into the flask over 5 hours and the polymerization initiator solution over 20 minutes. Further, immediately after the end of the supply of T1, the following mixture U was dropped over 30 minutes, and the temperature of 80 ° C. was further maintained for 1 hour 30 minutes (aging process). The polymerization reaction solution was sampled every hour from the start of dropping of T1, and after 7 hours, the reaction was stopped by cooling to room temperature. The value of the item shown in Table 1 was calculated | required from the sampled reaction liquid.

(S1)
2.07 parts (18.8 mol%) of monomer m-1;
9.15 parts (71.9 mol%) of monomer m-2,
1.44 parts (9.4 mol%) of monomer m-3,
92.7 parts ethyl lactate,
39.7 parts of PGMEA.
(T1)
42.84 parts (40 mol%) of monomer m-1
49.39 parts (40 mol%) of monomer m-2,
29.74 parts (20 mol%) of monomer m-3,
100.9 parts ethyl lactate,
49.5 parts of PGMEA,
3.069 parts dimethyl-2,2′-azobisisobutyrate (1.92 mol% relative to the total amount of monomers in S1 and T1).
(Polymerization initiator solution)
14.6 parts ethyl lactate,
0.767 parts of dimethyl-2,2′-azobisisobutyrate (0.48 mol% based on the total amount of monomers in S1 and T1).
(U)
0.33 part (66.7 mol%) of monomer m-1;
0.23 part (33.3 mol%) of monomer m-3,
12.6 parts of ethyl lactate,
5.4 parts of PMGEA 0.016 parts of dimethyl-2,2′-azobisisobutyrate (2.4 mol% relative to the amount of monomer in U).
[Purification of polymer]
In the same manner as in Example 1, the polymer was purified and evaluated. The evaluation results are shown in Table 2.

<Comparative example 4>
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer, 193.6 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, the dropping of the following mixture T1 was started from the dropping funnel and dropped into the flask over 4 hours. Furthermore, the temperature of 80 ° C. was maintained for 3 hours from the end of the supply of T1 (aging process). The polymerization reaction solution was sampled every hour from the start of dropping of T1, and after 7 hours, the reaction was stopped by cooling to room temperature. The value of the item shown in Table 1 was calculated | required from the sampled reaction liquid.

(T1)
81.60 parts (40 mol%) of monomer m-1
94.08 parts (40 mol%) of monomer m-2,
56.64 parts (20 mol%) of monomer m-3,
348.5 parts ethyl lactate,
6.900 parts of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S1 and T1).
12.6 parts of ethyl lactate,
5.4 parts of PMGEA 0.016 parts of dimethyl-2,2′-azobisisobutyrate (2.4 mol% relative to the total amount of monomers in U).
[Purification of polymer]
In the same manner as in Example 1, the polymer was purified and evaluated. The evaluation results are shown in Table 2.

<Comparative Example 5>
The following mixture S1 was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer 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, the following mixture T1 and the polymerization initiator solution were simultaneously fed from separate dropping funnels, and T1 was dropped into the flask over 4 hours and the polymerization initiator solution over 20 minutes. Furthermore, the temperature of 80 ° C. was maintained for 3 hours from the end of the supply of T1 (aging process). The polymerization reaction solution was sampled every hour from the start of dropping of T1, and after 7 hours, the reaction was stopped by cooling to room temperature. The value of the item shown in Table 1 was calculated | required from the sampled reaction liquid.

(S1)
2.72 parts (39.0 mol%) of monomer m-1
4.90 parts (41.3 mol%) of monomer m-2,
2.02 parts (19.7 mol%) of monomer m-3,
79.0 parts of ethyl lactate
(T1)
23.80 parts (40 mol%) of monomer m-1;
27.44 parts (40 mol%) of monomer m-2,
16.52 parts (20 mol%) of monomer m-3,
101.6 parts ethyl lactate,
0.643 parts of dimethyl-2,2′-azobisisobutyrate (0.7 mol% based on the total amount of monomers in S1 and T1).
(Polymerization initiator solution)
3.6 parts of ethyl lactate,
1.196 parts of dimethyl-2,2′-azobisisobutyrate (1.3 mol% based on the total amount of monomers in S1 and T1).
[Purification of polymer]
In the same manner as in Example 1, the polymer was purified and evaluated. The evaluation results are shown in Table 2.

<Comparative Example 6>
The following mixture S1 was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer 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, the following T1 and the polymerization initiator solution were simultaneously fed from separate dropping funnels, and the mixture T1 was dropped into the flask over 3 hours and the polymerization initiator solution over 20 minutes. Further, a temperature of 80 ° C. was maintained for 4 hours immediately after the end of the supply of T1 (aging process). The polymerization reaction solution was sampled every hour from the start of dropping of T1, and after 7 hours, the reaction was stopped by cooling to room temperature. The value of the item shown in Table 1 was calculated | required from the sampled reaction liquid.

(S1)
6.97 parts (34.2 mol%) of monomer m-1;
11.47 parts (48.8 mol%) of monomer m-2,
4.80 parts (17.0 mol%) of monomer m-3,
149.8 parts of PGMEA.
(T1)
Monomer m-1 73.44 parts (40 mol%),
84.67 parts (40 mol%) of monomer m-2,
50.98 parts (20 mol%) of monomer m-3,
149.5 parts of PGMEA,
3.864 parts of dimethyl-2,2′-azobisisobutyrate (1.4 mol% based on the total amount of monomers in S1 and T1).
(Polymerization initiator solution)
21.5 parts PGMEA,
7.175 parts of dimethyl-2,2′-azobisisobutyrate (2.6 mol% based on the total amount of monomers in S1 and T1).
[Purification of polymer]
In the same manner as in Example 1, the polymer was purified and evaluated. The evaluation results are shown in Table 2.

As shown in the results of Tables 1 and 2, Examples 1 to 3 have small variations in Mw of the polymer produced during 1 hour during the polymerization reaction period, and the weight average molecular weight y at the end of the polymerization reaction. The ratio of the standard deviation Z with respect to was 10% or less. In Examples 1 to 3, when a polymer was repeatedly produced under the same conditions, the variation in the average molecular weight (Mw) between lots was small, and the production reproducibility was excellent.
On the other hand, Comparative Examples 4 to 6 have a large variation in Mw of the polymer produced during one hour during the polymerization reaction period, and the ratio of the standard deviation Z to the weight average molecular weight y at the end of the polymerization reaction is 10 %, And the lot-to-lot difference in polymerization average molecular weight (Mw) is large. In particular, in Comparative Example 6 in which the mass ratio of the monomer supplied to the reaction liquid at the end of the polymerization reaction exceeds 40% by mass, the variation in Mw during the polymerization reaction period is particularly large, and there is also lot-to-lot variation. It was big.

Claims (4)

In the reaction vessel, two or more monomers, in the presence of a solvent, using a polymerization initiator, a polymerization step of performing a radical polymerization reaction, and a reaction termination step of stopping the polymerization reaction,
The polymerization rate is measured every hour after the start of the polymerization reaction, the polymerization rate is less than 90 mol% after n hours (n is an integer of 1 or more), and the polymerization rate after (n + 1) hours is 90 mol%. When it becomes more than
The value of the standard deviation Z of the weight-average molecular weight x _t of polymer produced respectively between the polymerization reaction started (t-1) times after ~t time after (t is an integer of 1 to n) is polymerized The ratio of the total mass of monomers supplied to the reaction vessel with respect to the mass of the reaction solution in the reaction vessel at the end of the polymerization reaction, which is 10% or less of the weight average molecular weight y at the end of the reaction. The manufacturing method of the polymer whose is 40 mass% or less. In the polymerization reaction period from the start of the polymerization reaction to the start of the operation for stopping the polymerization reaction, a monomer supply step for supplying the monomer continuously or dropwise into the reaction vessel ,
The method for producing a polymer according to claim 1, wherein the monomer is supplied over 70% or more of the polymerization reaction period. A step of producing a resist polymer by the production method according to claim 1 or 2,
A method for producing a resist composition, comprising a step of mixing the obtained resist polymer and a compound that generates an acid upon irradiation with actinic rays or radiation. A step of producing a resist composition by the production method according to claim 3;
Applying the obtained resist composition onto a work surface of a substrate to form a resist film;
A method for producing a substrate on which a pattern is formed, comprising a step of exposing the resist film and a step of developing the exposed resist film using a developer.

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