JP5771942B2 - Lithographic polymer manufacturing method, resist composition manufacturing method, and substrate manufacturing method - Google Patents

Description

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

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.

By the way, a polymer of (meth) acrylic acid ester is generally polymerized by a radical polymerization method. In general, in a multi-component polymer having two or more types of monomers, the copolymerization reactivity ratio between the monomers is different, so the copolymer composition ratio of the polymer produced in the early stage of polymerization and the late stage of polymerization is different, and the resulting polymer is It has a composition distribution.
If the composition ratio of the structural units in the copolymer varies, the solubility in the solvent tends to be low, and when preparing the resist composition, it takes a long time to dissolve in the solvent, or there is an insoluble content. Occurrence of this phenomenon may hinder the preparation of the resist composition, such as increasing the number of manufacturing steps. Further, the sensitivity of the resulting resist composition tends to be insufficient.
On the other hand, for example, in Patent Document 2 below, in order to obtain a resist having a high resolution, the supply ratio of the monomer having a relatively high polymerization rate and the monomer having a slow polymerization rate is changed between the previous step and the subsequent step. Describes a method for obtaining a polymer having a narrow copolymer composition distribution.

JP 2002-145955 A JP 2001-201856 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 content ratio of the constituent units in the copolymer, improve the solubility in a solvent, and the sensitivity when used in a resist composition. A production method, a polymer for lithography obtained by the production method, a resist composition using the polymer for lithography, and a method for producing a substrate on which a pattern is formed using the resist composition are provided. Objective.

In the first aspect of the present invention, two or more types of monomers α _{1 to} α _n (where n is 2 or more) are added in the reactor while dropping the monomer and the polymerization initiator into the reactor. (Representing an integer) is composed of structural units α ′ _{1 to} α ′ _n (where α ′ _{1 to} α ′ _n are structural units derived from monomers α _{1 to} α _n , respectively). A method for producing a polymer for lithography having a polymerization step for obtaining a polymer (P), comprising a plurality of solutions S1 to Sm (m is 2 or 3) containing monomers and having different monomer compositions And the polymerization step includes a main step of supplying the solutions S1 to S (m-1) into the reactor, respectively, and a post-step of supplying the solution Sm into the reactor after the main step is completed. When m = 2, the monomer composition of the solution S1 in the main process is the same as the target composition, and when m = 3, Said main monomer composition (unit: mol%) of the solution S1 in the step of _{α 11: α 12: ...:} α expressed in _1n, the following (1) ~ _F 1 Factor obtained in the procedure (3), F ₂ ,... F _n , α ₁₁ = α ′ ₁ / F ₁ , α ₁₂ = α ′ ₂ / F ₂ ,... Α _1n = α ′ _n / F _n , and the monomer composition of the solution S2 is is the same as the target composition, said a 0.1 to 10 mass% of the total amount of the monomers contained in the solution Sm is total monomer feed rate solution Sm is monomeric alpha ₁ to? _n Among them, the monomer with the slowest copolymerization reaction rate is not included,
In the subsequent step, the target composition (unit: mol%) representing the content ratio of the structural units α ′ _{1 to} α ′ _n in the polymer (P) is α ′ ₁ : α ′ ₂ :...: Α ′ _n when the composition of the monomer solution Sm contains (unit: mol%) of _{α m1: α m2: ...:} α expressed in _mn, the following (1) ~ (3) _{F 1} factor obtained in the procedure , F ₂ ,... F _n ( _where the smallest of F _{1 to} F _n is replaced with 0), α _m1 = α ′ ₁ × F ₁ / (α ′ ₁ × F ₁ + α ′) ₂ × F ₂ +... + Α ′ _n × F _n ), α _m2 = α ′ ₂ × F ₂ / (α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + Α ′ _n × F _n ) _,. = Α ′ _n × F _n / (α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + Α ′ _n × F _n ) A method for producing a polymer for lithography.
(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 r} until _{t r + 1} (r is 1 or more Find an integer.)
(3) _P in the "during the period from _{t r} to _{t r + 1" 1:} P _{2: ...:} and the value of _{P n, M} in the elapsed time _{t r 1: M 2: ...} : from the value of _{M n,} the following 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 .

The second aspect of the present invention is a method for producing a polymer for lithography by the method for producing a polymer for lithography of the present invention, and the resulting polymer for lithography and generation of an acid by irradiation with actinic rays or radiation. It is a manufacturing method of the resist composition which has the process of mixing a compound.
According to a third aspect of the present invention, there is provided a step of producing a resist composition by the method for producing a resist composition of the present invention, and applying the obtained resist composition onto a work surface of a substrate to form a resist film And a step of exposing the resist film, and a step of developing the exposed resist film using a developer.

According to the method for producing a lithographic polymer of the present invention, there is provided a lithographic polymer that can improve variation in the content ratio of structural units, improve solubility in a solvent, and sensitivity when used in a resist composition. can get.
The lithographic polymer of the present invention has improved variation in the content ratio of structural units and variation in molecular weight, 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. 3 is a graph showing the results of Example 1. 10 is a graph showing the results of Example 2. 6 is a graph showing the results of Comparative Example 1. 10 is a graph showing the results of Reference Example 2. 10 is a graph showing the results of Example 3. It is a graph which shows the result of Example 4. 10 is a graph showing the results of Reference Example 3. 10 is a graph showing the results of Example 5. 10 is a graph showing the results of Example 6.

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 a light absorbing group include benzyl (meth) acrylate (m-6 in Examples), p-hydroxyphenyl (meth) acrylate, and the like.

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 that the structural unit which has this is included.
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 (m-2 in Examples), 2-methyl-2-adamantyl methacrylate (m-5 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 m-1), α-acryloyloxy-γ-butyrolactone (Example m-4), 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 (m-7 in Examples), 3-hydroxypropyl (meth) acrylate, (meth ) 2-hydroxy-n-propyl acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl- Examples include 2-adamantyl (meth) acrylate. 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 (m-3 in Examples) and 2-cyanomethyl-2-adamantyl methacrylate 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 (hereinafter sometimes referred to as “PGME”), etc.), 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.

In the present invention, as the liquid containing the monomer, a plurality of solutions S1 to Sm (m is an integer of 2 or more) having different monomer compositions are used. The solutions S1 to Sm preferably contain a solvent. The upper limit of m is not particularly limited, but is preferably 4 or less and more preferably 3 or less from the viewpoint of ease of control and operation.
The polymerization process in the present invention includes a main process for supplying the solutions S1 to S (m-1) into the reactor, and a post-process for supplying the solution Sm into the reactor after the main process is completed. The main step is preferably controlled such that the content ratio of the constituent units in the polymer produced in the reaction vessel by dropping the monomer solution is close to the target composition.

<Main process>
First, the main process will be described.
The main process should just be the dripping polymerization method which has the process of supplying 1 or more types of monomer solutions by dripping, and can be performed using a well-known method suitably. Preferred embodiments include the following first embodiment or second embodiment.
[First Embodiment of Main Process]
An embodiment is preferred in which only one monomer solution is used in the main step and the solution S1 having the same monomer composition as the target composition is dropped into the reaction vessel.
In the present embodiment, the composition (mol%) of the solution S1 is most preferably the same as the target composition (mol%), but within a range of ± 10% with respect to the target composition, preferably ± 5%. If the error is within the range, it is allowed. That is, within the error range, it is assumed that the composition of the solution S1 and the target composition are the same.

[Second Embodiment of Main Process]
As a method of using two kinds of monomer solutions in the main process, before dropping the polymerization initiator into the reactor or simultaneously with the start of dropping of the polymerization initiator, the monomers α ₁ to. Supply of the first solution (S1) containing α _n in the first composition is started and supply of the first solution (S1) is started after the start of supply of the first solution (S1) into the reactor. Simultaneously with the start, dropping of the second solution (S2) containing the monomers α _{1 to} α _n in the second composition in the reactor is started, and before the end of dropping of the second solution (S2). In addition, a method of terminating the supply of the first solution (S1) is preferable.
Hereinafter, a second embodiment of the main process will be described.
[Second solution (S2)]
The content ratio (second composition) of the monomer in the second solution (S2) 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. It is.
For example, the polymer (P) is a ternary polymer obtained by copolymerizing monomers x, y, and z, and the target composition (mol%, the same applies hereinafter) is x ′: y ′. : Z ′, the second composition (mol%, the same shall apply hereinafter) x: y: z is the same as x ′: y ′: z ′.
In the present embodiment, in order to obtain the desired effect, the second composition (mol%) is most preferably the same as the target composition (mol%), but ± 10% with respect to the target composition. Error, preferably within ± 5%. That is, within the error range, it is assumed that the second composition and the target composition are the same.
The second solution is fed dropwise to the reactor.

[First Solution (S1)]
The monomer content ratio (first composition) in the first solution (S1) is obtained in advance by taking into account the target composition in the polymer (P) and the reactivity of each monomer used in the polymerization. Composition.
Specifically, the first composition of the first solution (S1) is such that when the content ratio of the monomer present in the reactor is the first composition, the second solution (S1) is contained in the reactor. When S2) is dropped, the composition is designed so that the content ratio of the constituent units of the polymer molecules generated immediately after dropping is the same as the target composition. In this case, since the content ratio of the constituent units of the polymer molecules generated immediately after the dropping is the same as the monomer content ratio (target composition) of the dropped second solution (S2), immediately after the dropping. The content ratio of the monomer remaining in the reactor is always constant (first composition). Therefore, when the dropping of the second solution (S2) is continuously performed in the reactor, a steady state in which polymer molecules having a target composition are always generated can be obtained.
That is, according to the present embodiment, polymer molecules having the same composition as the target composition are generated immediately after the start of the polymerization reaction, and the state continues, so that the polymer generated in the main process contains constituent units. The variation in the ratio is reduced.
The existence of the first composition that can provide such a steady state is a finding obtained for the first time by the present inventors. The design method of the first composition will be described later.
The first solution (S1) may be charged into 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 second solution (S2) may contain a polymerization initiator. When dropping the first solution (S1), the first solution (S1) may contain a polymerization initiator. In addition to the first solution (S1) and the second solution (S2), a solution containing a polymerization initiator (polymerization initiator solution) may be added dropwise. These may be combined.
The amount of polymerization initiator used in the main process (total supply in the main process) is set according to the type of polymerization initiator and the target value of the weight average molecular weight of the polymer (P) to be obtained. The
For example, when the polymer (P) in the present invention is a lithography polymer, the polymerization is performed with respect to 100 mol% of the total amount of monomers supplied to the reactor in the main step (total supply amount in the main step). The use amount of the initiator (total supply amount in the main process) is preferably in the range of 1 to 25 mol%, more preferably in the range of 1.5 to 20 mol%.

[Monomer Content in First Solution (S1)]
The total amount of monomers used in the polymerization step (total monomer supply amount) is the sum of the monomers contained in the solutions S1 to S (m-1), and the polymer (P ).
Further, if the ratio of the total amount of monomers contained in the first solution (S1) in the total monomer supply amount is too small, the desired effect by using the first solution (S1) Is not obtained sufficiently, and if it is too much, the molecular weight of the polymer produced at the initial stage of the polymerization process becomes too high. Therefore, 3-40 mass% is preferable and, as for the total amount of the monomer contained in a 1st solution (S1) with respect to the total monomer supply amount, 5-30 mass% is more preferable.

[Supply of first solution (S1) and second solution (S2)]
In the main process, when the polymerization initiator is dropped into the reactor, it is necessary that the first solution (S1) exists in the reactor. Accordingly, 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 (S1) into the reactor is started.
In addition, when the second solution (S2) is dropped into the reactor, the first solution (S1) needs to be present in the reactor. Therefore, after starting the supply of the first solution (S1) into the reactor or simultaneously with the start of the supply of the first solution (S1), the dropping of the second solution (S2) is started in the reactor. The start of dropping of the second solution (S2) is preferably simultaneous with the start of dropping of the polymerization initiator or after the start of dropping of the polymerization initiator. The start of dropping the polymerization initiator and the start of dropping the second solution (S2) are preferably simultaneous. Prior to the end of dropping of the second solution (S2), the supply of the first solution (S1) is ended.
The dropping of the second solution (S2) 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 1st solution (S1) 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.

The first solution (S1) is supplied at its initial stage in the polymerization step. Specifically, when the reference time is from the start of dropping of the polymerization initiator to the end of dropping of the second solution (S2), It is preferable to end the supply of the first solution (S1) before 20% of the reference time has elapsed. For example, when the reference time is 4 hours, it is preferable to supply the entire amount of the first solution (S1) into the reactor before 48 minutes have elapsed from the start of the dropping of the polymerization initiator.
The end of the supply of the first solution (S1) is preferably 15% or less of the reference time, and more preferably 10% or less.
Further, the entire amount of the first solution (S1) may be supplied at the time of 0% of the reference time. That is, the entire amount of the first solution (S1) may be charged in the reactor before the start of dropping of the polymerization initiator.

[Polymerization initiator supply rate]
In the present embodiment, the dropping of the polymerization initiator in the main step may be performed until the dropping of the second solution (S2) is completed, or may be ended before that. It is preferable to carry out until the end of dropping of the second solution (S2).
Although the supply rate of the polymerization initiator may be constant, in particular, by increasing the supply amount at the initial stage of the polymerization process, the generation of high molecular weight components (high polymer) at the initial stage of polymerization is suppressed, and as a result, the polymerization process is finished The variation in molecular weight in the polymer obtained can be reduced. Such uniform molecular weight contributes to the improvement of the solubility of the lithography polymer in the resist solvent and the solubility in the alkaline developer, and also contributes to the improvement of the sensitivity of the resist composition.
The weight average molecular weight of the polymer produced at the initial stage of the polymerization process varies depending on the supply amount of the polymerization initiator at the initial stage of the polymerization process. Therefore, the optimum supply rate 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., but the polymer produced particularly at the initial stage of the polymerization step. It is preferable that the weight average molecular weight is set to be close to the target value.
Specifically, in the initial stage before 5 to 20% of the reference time elapses, 30 to 90% of the total supply amount of the polymerization initiator used in the main process is supplied, and thereafter from the initial stage. However, it is preferable to supply the polymerization initiator at a low speed.
The initial stage is preferably 5.5 to 17.5% of the reference time, and more preferably 6 to 15%. The supply amount of the polymerization initiator in the initial stage is more preferably 35 to 85% by mass, and further preferably 40 to 80% by mass, based on the total supply amount of the polymerization initiator used in the main process.

[Preferred embodiment of main process]
The following (a) and (b) are mentioned as a preferable aspect of the main process in this embodiment.
(A) After first charging the reactor with the first solution (S1) containing the monomers α _{1 to} α _n in the first composition and heating the reactor to a predetermined polymerization temperature, In the reactor, a polymerization initiator solution containing a part of the polymerization initiator supplied in the main step and the monomers α _{1 to} α _n are contained in the second composition, and the remainder of the polymerization initiator is contained. The 2nd solution (S2) containing is dripped, respectively. The polymerization initiator solution and the second solution (S2) start dropping simultaneously, or the polymerization initiator solution starts dropping first. Simultaneous is preferred. The time from the start of dropping of the polymerization initiator solution to the start of dropping of the second solution (S2) is preferably 0 to 10 minutes.
The dropping speed is preferably constant. The polymerization initiator solution ends dropping before the second solution (S2).

(B) After charging only the solvent into the reactor and heating it to a predetermined polymerization temperature, the monomer α _{1 to} α _n is contained in the first composition and one of the polymerization initiators supplied in the main process first with a solution (S1) containing part, along with containing monomer alpha ₁ to? _n in the second composition, it is dropped a second solution containing the remainder of the polymerization initiator (S2), respectively. Both liquids start dropping simultaneously, or the first solution (S1) starts dropping first. The time from the start of dropping of the first solution (S1) to the start of dropping of the second solution (S2) is preferably 0 to 10 minutes.
The dropping speed is preferably constant. The first solution (S1) finishes dropping more than the second solution (S2).

<Design method of first composition of first solution (S1)>
Hereinafter, a preferable 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 ₁₁ : α ₁₂ :... Α _1n , and the factors determined by the following procedures (1) to (3) are represented by F ₁ , F ₂ ,... F _n , and α ₁₁ = α ′. ₁ / F ₁ , α ₁₂ = α ′ ₂ / F ₂ ,... Α _1n = α ′ _n / F _n .
(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 r} until _{t r + 1} (r is 1 or more Find an integer.)
(3) _P in the "during the period from _{t r} to _{t r + 1" 1:} P _{2: ...:} and the value of _{P n, M} in the elapsed time _{t r 1: M 2: ...} : from the value of _{M n,} the following 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 ₀₀ : y ₀₀ : z ₀₀ is obtained by using the factors Fx, Fy, and Fz obtained by the following method, and x ₀₀ = x ′ / It is assumed that Fx, y ₀₀ = y ′ / Fy, z ₀₀ = 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) Px: Py: Pz is, the target composition x ': y': "Between _{t r} to _{t r + 1} (. R is an integer of 1 or more)" closest time zone z 'find.
(3) Px in its "during the period from _{t r} to _{t r + 1":} Py: the value of Pz, Mx at the elapsed time _{t r:} My: from the value of Mz and, by the following equation, factor Fx, Fy, and Fz 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.
In the present embodiment, when the first composition is designed using the above factors, the first composition (mol%) is the same as the design value (mol%) in obtaining the desired effect. Most preferably, an error within a range of ± 10%, preferably within a range of ± 5% with respect to the design value is acceptable. That is, within the error range, it is assumed that the first composition and the design value designed using the above factor are the same.

<Post process>
In the post-process, the solution Sm is dropped into the reactor in which the supply of the solutions S1 to S (m-1) used in the main process is completed.
[Solution Sm]
The solution Sm does not contain a monomer having the slowest copolymerization reaction rate among the monomers α _{1 to} α _n . It is preferable that the monomer in the solution Sm does not include only the monomer having the slowest copolymerization reaction rate among the monomers α _{1 to} α _n and includes other monomers.
The total amount of monomers contained in the solution Sm is 0.1 to 10% by mass, preferably 0.1 to 7.5% by mass, more preferably 0, based on the total amount of monomers used in the polymerization step. 0.1 to 5% by mass. When the content is 0.1% by mass or more, it is easy to obtain a sufficient effect by providing a post-process. When it is 10% by mass or less, 7.5% by mass or less, or 5% by mass or less, an effect of reducing variation in polymer composition is easily obtained.

The composition of the monomer in the solution Sm is designed by the following method using the same factor except that the smallest one of the factors (F _{1 to} F _n ) in the design method of the first composition is replaced with 0. The composition is preferred.
That is, the target composition representing the content of the structural unit α _'1 ~α' _n in the polymer to be obtained (P) (unit: mol%) of _{α '1: α' 2:} ...: is alpha _'n When the composition (unit: mol%) of the monomer contained in the solution Sm is represented by α _m1 : α _m2 :...: Α _mn , the same as the design method of the first composition (1) to (3) When the factors determined by the procedure are _expressed as F ₁ , F ₂ ,... F _n ( _where the smallest one of F _{1 to} F _n is replaced with 0), α _m1 = α ′ ₁ × F ₁ / ( α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + α ′ _n × F _n ), α _m2 = α ′ ₂ × F ₂ / (α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + α ′ _n × F _n ),... Α _mn = α ′ _n × F _n / (α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + Α ′ _n × F _n ).
In the present invention, when the composition of the monomer of the solution Sm is designed using the above factors, the composition (mol%) of the monomer of the solution Sm is the design value (in order to obtain the desired effect). Most preferably, the error is within a range of ± 10%, preferably within a range of ± 5% with respect to the design value. That is, within this error range, the composition of the monomer of the solution Sm and the design value designed using the above factors are assumed to be the same.

It is preferable that the solution Sm starts dropping immediately after the dropping of S1 to S (m-1) is completed.
The dropping of the solution Sm may be continuous or intermittent, and the dropping speed may be changed. It is preferable that the supply amount of the monomer per unit time supplied into the reactor by dropping of the solution Sm gradually or stepwise decreases with the passage of time.
For example, as the solution Sm, one type of solution in which the monomer composition and the monomer content (concentration) are both uniform may be used, and the dropping rate may be decreased continuously or in stages. May be. Alternatively, as the solution Sm, two or more liquids having the same monomer composition (the above error range is allowed) but different monomer contents (concentrations) may be used. In this case, even when the dropping rate is constant, the supply of the monomer per unit time is gradually or stepwise by dropping two or more liquids sequentially so that the monomer concentration decreases. Can be reduced.
Specifically, the time from the start of dropping of the solution Sm to the end of dropping is set as the post-dropping time, and the value obtained by dividing the total supply amount of the monomer in the post-process by the post-dropping time is set as the average supply rate. A period from 0% to k% (k is 5 to 95) is a high-speed supply period in which the monomer is supplied at a speed higher than the average supply speed. It is preferable to supply 50 to 95% by mass of the amount into the reactor.
The k is more preferably 20 to 80%, further preferably 30 to 70%. The monomer supplied into the reactor during the high-speed supply period is more preferably 60 to 90% by mass, and more preferably 70 to 85% by mass, out of the total supply amount of monomers in the subsequent step.

In the subsequent step, when the solution Sm is dropped into the reactor, it is necessary that a polymerization initiator is present in the reactor. Therefore, it is preferable to supply the polymerization initiator into the reactor also in the post-process.
The solution Sm may contain a polymerization initiator, and separately from the solution Sm, a solution containing a polymerization initiator (polymerization initiator solution) may be dropped. These may be combined.
For example, when the polymer (P) in the present invention is a polymer for lithography, 100 mol% of the total amount of monomers supplied to the reactor in the post-process (total supply amount of monomers in the post-main process) On the other hand, the use amount of the polymerization initiator (total supply amount of the polymerization initiator in the post-process) is preferably in the range of 1 to 25 mol%, more preferably in the range of 1.5 to 20 mol%.

  After completion of the post-process, that is, after completion of the dropping of the solution Sm, a holding process for maintaining the inside of the reactor at the polymerization temperature, a cooling process, a purification process, and the like can be appropriately performed as necessary.

According to the knowledge of the present inventors, in the dropping polymerization, even if the monomer unit solution is dropped to control the content ratio of the structural unit in the polymer produced in the reaction vessel to be close to the target composition, When the dropping of the monomer solution is completed and the holding step is started, the difference between the content ratio of the structural unit in the produced polymer and the target composition gradually widens. Specifically, the longer the elapsed time in the holding step, the more significantly the composition ratio of the structural units derived from the monomer having the slowest copolymerization reaction rate in the produced polymer. From this, at the end of dropping of the monomer solution, it is considered that the monomer having the slowest copolymerization reaction rate remains in the reactor excessively with respect to the target composition.
In the present invention, after the main step, the holding step is not performed as it is, and a post-step is added to drop the solution Sm containing no monomer having the slowest copolymerization reaction rate. Supply monomers other than the slowest monomer. As a result, in the reactor at the end of dropping of the solutions S1 to S (m-1), the monomer having the slowest copolymerization reaction rate remaining excessively with respect to the target composition is efficiently consumed while being efficiently consumed. Since the coalescence can be generated, the difference between the content ratio of the structural unit in the polymer produced after the main process and the target composition is prevented from spreading over time. Therefore, the dispersion | variation in the content rate of the structural unit in the polymer (P) finally obtained can be reduced.

Moreover, the content ratio of the structural unit in the polymer produced | generated after the main process can be made closer to a target composition by making the monomer composition of solution Sm into the composition obtained by the design method using said factor. .
Furthermore, in the subsequent step, by reducing the supply amount per unit time of the monomer (monomer other than the monomer having the slowest copolymerization reaction rate) supplied by dropping the solution Sm with time, In the reactor, since the monomer with the slowest copolymerization reaction rate is consumed and the shortage relative to the target composition can be suppressed, the amount of monomer present in the reactor can be reduced. It is preferable when producing a polymer having a monomer composition close to the target composition.
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, 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.

<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 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, the separation column is manufactured by GL Sciences, using one Inertsil ODS-2 (trade name), 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. After judging complete dissolution visually, heptane was added until the cloud point was reached, and the amount of heptane added was measured. . The determination of cloud point arrival was made visually.

(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 composition of solution Sm used in post-process>
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%) This is an example in which the composition of Sm in the case of producing a polymer having a weight average molecular weight target value of 10,000 is obtained.
The polymerization initiator used in this example is dimethyl-2,2′-azobisisobutyrate (V601 (trade name)). The polymerization temperature was 80 ° C.

In a flask (reactor) 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 containing the following monomer mixture, solvent, and polymerization initiator was dropped into the flask at a constant dropping rate over 4 hours from the dropping funnel, and the temperature of 80 ° C. was further 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 3, 4, 5, 6, and 7 hours from the start of the dropping of the dropping solution, 0.5 g of the polymerization reaction solution in the flask was sampled, and each of the monomers m-1 to m-3 was quantified. Thereby, the mass of each monomer remaining in the flask at the time of each sampling is known. As a result, for example, the results after 3 hours and 4 hours from 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 flask at each sampling time (corresponding to Mx: My: Mz).
As a result, for example, the results after 3 hours and 4 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 flask at a constant rate for 4 hours. By subtracting the mass of each monomer remaining in the sample, the mass of each monomer that had been converted to a polymer among the monomers supplied up to that time was calculated for each monomer.
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 4 hours corresponds to the data of the polymer produced 3 to 4 hours after the start of dropping (the same applies hereinafter).

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 3 hours to 4 hours after the start of dropping. The polymer was Px: Py: Pz = 41: 38: 20.
Using this value and the value of Mx: My: Mz after 3 hours from the start of dropping (Table 2), Fx = Px / Mx, Fy = Py / My, Fz = Pz / Mz, and factor Fx , Fy, and Fz are obtained as Fx = 1.31, Fy = 0.72, and Fz = 1.23. At this time, Fy is replaced with 0 from Fy <Fz <Fx.
The Sm composition x ₀ : y ₀ : z ₀ was determined using the factor value and the target composition.
x ₀ = 40 × Fx / (40 × Fx + 40 × Fy + 20 × Fz)
= 40 x 1.31 / (40 x 1.31 + 40 x 0 + 20 x 1.23) = 68.1 mol%.
y ₀ = 40 × Fy / (40 × Fx + 40 × Fy + 20 × Fz)
= 40 x 0 / (40 x 1.31 + 40 x 0 + 20 x 1.23) = 0 mol%.
z ₀ = 20 × Fz / (40 × Fx + 40 × Fy + 20 × Fz)
= 20 x 1.23 / (40 x 1.31 + 40 x 0 + 20 x 1.23) = 31.9 mol%.

<Example 1>
In this example, a post-step for dropping S2 was provided after the main step for dropping solution S1 (in the present specification, sometimes simply referred to as S1, and the same applies to S2, S3...).
The composition of Sm obtained in Reference Example 1 was defined as the composition of S2. 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 monomer composition of S1 was the same as the target composition.
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.
Then, after dripping the whole amount of the following S1 into the flask over 4 hours from the dropping funnel, immediately dropping 80% by mass of the following S2 over 1 hour, and then adding the remaining 20% by mass over 1 hour. It was dropped and the temperature of 80 ° C. was further maintained for 1 hour. Seven hours after the start of dropping of the S1 solution, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S2 is 2.18% by mass of the total monomer supply amount.

(S1)
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,
87.5 parts ethyl lactate,
2.415 parts of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S1).
(S2)
1.10 parts (68.1 mol%) of monomer m-1;
0.72 parts (31.9 mol%) of monomer m-3,
34.5 parts ethyl lactate,
0.054 part of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S2).

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.
Comparing the results of FIG. 1 and FIG. 2, in Reference Example 1 (FIG. 1), the reaction time from 4 hours at the end of the main process (end of the dropping liquid) to the reaction time of 7 hours at the end of the holding process In the polymer produced in the meantime, the difference between the polymer composition ratio and the target composition increases with time.
On the other hand, in Example 1 (FIG. 2) in which a post-process for supplying S2 for a total of 2 hours after the end of the main process (end of dropping S1) was provided, after the end of the main process (reaction time 4 hours) The composition ratio of the polymer was very close to the target composition, and the variation in the composition ratio due to the reaction time was improved.

[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 7.

[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 7.

<Example 2>
In this example, S1 was supplied into the reactor in advance, and a post-process for dropping S3 was provided after the main process for dropping S2 and the polymerization initiator solution.
The composition of Sm obtained in Reference Example 1 was defined as the composition of S3. 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 monomer composition of S1 was the same as the first composition designed by the method using the above factors, and the monomer composition of S2 was the same as the target composition.
[Design of first composition of S1]
The first composition was determined using the factor values (Fx = 1.27, Fy = 0.76, Fz = 1.22) determined in Reference Example 1 and the target composition, and this was determined as the monomer composition of S1. It was.
_{x 00 = 40 / Fx = 40} / 1.27 = about 31.3 mole%.
_{y 00 = 40 / Fy = 40} / 0.76 = about 52.4 mole%.
_{z 00 = 20 / Fz = 20} / 1.22 = about 16.3 mole%.

The following 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 S2 polymerization initiator solution was simultaneously fed from a separate dropping funnel, and S2 was dropped into the flask over 4 hours and the polymerization initiator solution over 20 minutes. Further, immediately after the supply of S2, 80% by mass of S3 below was added dropwise over 1 hour, the remaining 20% by mass was added dropwise over 1 hour, and the temperature of 80 ° C. was maintained for 1 hour. Seven hours after the start of dropping S2, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S3 is 2.15% by mass of the total monomer supply amount.

(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.
(S2)
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 S2).
(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 S2).
(S3)
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 of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S3).

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.
Compared to Reference Example 1 (FIG. 1), Example 2 (FIG. 3) is the end of the main process by providing a post-process for supplying S3 for a total of 2 hours after the end of the main process (end of dropping S2). Even after (reaction time 4 hours), the polymer composition ratio showed a value very close to the target composition, and the variation in composition ratio due to the reaction time was improved.

[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 7 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 7.

<Comparative Example 1>
In Example 1, the total amount of monomers contained in S2 dropped in the subsequent step was changed to 15.67% by mass of the total monomer supply amount.
That is, the same procedure as in Example 1 was performed except that the compositions of S1 and S2 were changed as follows.
(S1)
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,
99.3 parts ethyl lactate,
2.415 parts of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S1)
(S2)
9.07 parts (67.6 mol%) of monomer m-1;
6.05 parts (32.4 mol%) of monomer m-3,
22.7 parts of ethyl lactate,
0.454 parts of dimethyl-2,2′-azobisisobutyrate (2.5 mol% based on the total amount of monomers in S2).

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.
Compared with Example 1 (FIG. 2), Comparative Example 1 (FIG. 4) has an excessive proportion of monomers supplied in the subsequent step out of the total monomer supply amount. The difference between the polymer composition ratio of the polymer produced after 4 hours) and the target composition is large, and the dispersion of the polymer composition is large depending on the reaction time.

<Reference Example 2: Design of composition of solution Sm used in post-process>
This example polymerizes monomers m-4, m-5, and m-3 represented by the following formulas (m-4) and (m-5) and the above formula (m-3) to obtain a target composition. M-4: m-5: m-3 = 35: 35: 30 (mol%), in the case where a polymer having a weight average molecular weight target value of 7,000 was produced, the Sm composition was obtained. is there.
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, 31.7 parts of ethyl lactate and 31.7 parts of PGMEA were 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 containing the following monomer mixture, solvent, and polymerization initiator was dropped from the dropping funnel into the flask at a constant dropping rate over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours. Seven hours after the start of dropping of the dropping solution, the reaction was stopped by cooling to room temperature.
20.83 parts (35 mol%) of monomer m-4,
30.38 parts (35 mol%) of monomer m-5,
24.78 parts (30 mol%) of monomer m-3,
57.0 parts ethyl lactate,
57.0 parts PGMEA,
4.508 parts of dimethyl-2,2′-azobisisobutyrate (5.6 mol% based on the total amount of monomers fed).

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

Next, the molecular weight of each monomer was used to convert the molar fraction of each monomer remaining in the flask at each sampling time (corresponding to Mx: My: Mz).
As a result, for example, the results after 3 hours and 4 hours after the start of dropping were as shown in Table 4.

In the same manner as in Reference Example 1, the content ratio of the structural unit in the polymer produced in each reaction time zone was determined. The result is shown in FIG.
As shown in the results of FIG. 5, the polymer composition ratio (Px: Py: Pz) is the closest to the target composition 35:35:30, which was generated 3 to 4 hours after the start of dropping. It was a polymer, and Px: Py: Pz = 37.36: 32.61: 28.95.
Using this value and the value of Mx: My: Mz after 3 hours from the start of dropping (Table 4), Fx = Px / Mx, Fy = Py / My, Fz = Pz / Mz, factor Fx , Fy, and Fz are obtained as Fx = 1.60, Fy = 0.60, and Fz = 1.50. At this time, Fy is replaced with 0 from Fy <Fz <Fx.
The Sm composition x ₀ : y ₀ : z ₀ was determined using the factor value and the target composition.
x ₀ = 35 × Fx / (35 × Fx + 35 × Fy + 30 × Fz)
= 35 x 1.60 / (35 x 1.60 + 35 x 0 + 30 x 1.50) = 55.4 mol%.
y ₀ = 35 × Fy / (35 × Fx + 35 × Fy + 30 × Fz)
= 35 x 0 / (35 x 1.60 + 35 x 0 + 30 x 1.50) = 0 mol%.
z ₀ = 30 × Fz / (35 × Fx + 35 × Fy + 30 × Fz)
= 30 x 1.50 / (35 x 1.60 + 35 x 0 + 30 x 1.50) = 44.6 mol%.

<Example 3>
In this example, a post-process for dropping S2 was provided after the main process for dropping S1.
The composition of Sm obtained in Reference Example 2 was used as the composition of S2. 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 2. The monomer composition of S1 was the same as the target composition.
In a flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer, 31.7 parts of ethyl lactate and 31.7 parts of PGMEA were 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.
Then, after dripping the whole amount of the following S1 into the flask over 4 hours from the dropping funnel, immediately dropping 80% by mass of the following S2 over 1 hour, and then adding the remaining 20% by mass over 1 hour. It was dropped and the temperature of 80 ° C. was further maintained for 1 hour. Seven hours after the start of dropping of the S1 solution, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S2 is 2.71% by mass of the total monomer supply amount.

(S1)
20.83 parts (35 mol%) of monomer m-4,
30.38 parts (35 mol%) of monomer m-5,
24.78 parts (30 mol%) of monomer m-3,
40.4 parts ethyl lactate,
40.4 parts PGMEA,
4.508 parts of dimethyl-2,2′-azobisisobutyrate (5.6 mol% based on the total amount of monomers in S1).
(S2)
1.00 parts (55.4 mol%) of monomer m-4,
1.12 parts (44.6 mol%) of monomer m-3,
16.6 parts of ethyl lactate,
16.6 parts PGMEA,
0.137 parts of dimethyl-2,2′-azobisisobutyrate (5.6 mol% based on the total amount of monomers in S2).

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.
Comparing the results of FIG. 5 and FIG. 6, in Reference Example 2 (FIG. 5), the reaction time of 4 hours at the end of the main process (end of the dropping liquid) to the reaction time of 7 hours at the end of the holding process is increased. In the polymer produced in the meantime, the difference between the polymer composition ratio and the target composition increases with time.
On the other hand, in Example 3 (FIG. 6) in which a post-process for supplying S2 for a total of 2 hours after the end of the main process (end of dropping S1) was provided, after the end of the main process (reaction time 4 hours) The composition ratio of the polymer was very close to the target composition, and the variation in the composition ratio due to the reaction time was improved.

[Purification of polymer]
The 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. The polymerization reaction in the flask after 7 hours of reaction time was carried out in the same manner as in Example 1 except that the solvent (methanol / water = 85/15 volume ratio) and (methanol / water = 95/5 volume ratio) were changed. From the solution, a polymer P3 was obtained. Table 7 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 7.

<Example 4>
In this example, S1 was supplied into the reactor in advance, and a post-process for dropping S3 was provided after the main process for dropping S2 and the polymerization initiator solution.
The composition of Sm obtained in Reference Example 2 was used as the composition of S3. 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 2. The monomer composition of S1 was the same as the first composition designed by the method using the above factors, and the monomer composition of S2 was the same as the target composition.
[Design of first composition of S1]
The first composition was determined using the factor values determined in Reference Example 2 (Fx = 1.60, Fy = 0.60, Fz = 1.50) and the target composition, and this was determined as the monomer composition of S1. It was.
_{x 00 = 35 / Fx = 35} / 1.60 = about 21.8 mole%.
_{y 00 = 35 / Fy = 35} / 0.60 = about 58.2 mole%.
z ₀₀ = 30 / Fz = 30 / 1.50 = about 20.0 mol%.
The following 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.
Then, the following S2 and the polymerization initiator solution were simultaneously fed from separate dropping funnels, and S2 was dropped into the flask over 4 hours and the polymerization initiator solution over 20 minutes. Further, 80% by mass of S3 below was dropped over 1 hour immediately after the supply of S2, and then the remaining 20% by mass was dropped over 1 hour, and the temperature of 80 ° C. was maintained for 1 hour. Seven hours after the start of dropping of the solution of S2, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S3 is 2.68% by mass of the total monomer supply amount.

(S1)
2.60 parts (21.8 mol%) of monomer m-4,
10.13 parts (58.2 mol%) of monomer m-5,
3.30 parts (20.0 mol%) of monomer m-3,
46.5 parts ethyl lactate,
46.5 parts PGMEA.
(S2)
16.66 parts (35 mol%) of monomer m-4,
24.30 parts (35 mol%) of monomer m-5,
24.00 parts (30 mol%) of monomer m-3,
26.9 parts of ethyl lactate,
33.4 parts PGMEA,
1.450 parts of dimethyl-2,2′-azobisisobutyrate (1.8 mol% relative to the total amount of monomers in S1 and S2).
(Polymerization initiator solution)
6.5 parts ethyl lactate,
2.174 parts of dimethyl-2,2′-azobisisobutyrate (2.7 mol% based on the total amount of monomers in S1 and S2).
(S3)
1.00 parts (55.4 mol%) of monomer m-4,
1.12 parts (44.6 mol%) of monomer m-3,
12.2 parts ethyl lactate,
12.2 parts of PGMEA,
0.110 parts of dimethyl-2,2′-azobisisobutyrate (4.5 mol% based on the total amount of monomers in S3).

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.
Compared to Reference Example 2 (FIG. 5), Example 4 (FIG. 7) is the end of the main process by providing a post-process for supplying S3 for a total of 2 hours after the end of the main process (end of dropping S2). Even after (reaction time 4 hours), the polymer composition ratio showed a value very close to the target composition, and the variation in composition ratio due to the reaction time was improved.

[Purification of polymer]
In the same manner as in Example 3, polymer P4 was obtained from the polymerization reaction solution in the flask after 7 hours of reaction time. Table 7 shows the results of Mw, Mw / Mn and solubility evaluation of the polymer P4.
[Production of resist composition]
In the same manner as in Example 1, a resist composition containing the polymer P4 was prepared, and the sensitivity was evaluated. The results are shown in Table 7.

<Reference example 3: Design of composition of solution Sm used in post-process>
This example polymerizes monomers m-1, m-6, and m-7 represented by the above formula (m-1) and the following formulas (m-6) and (m-7) to obtain a target composition. M-1: m-6: m-7 = 25: 25: 50 (mol%), in the case of producing a polymer having a weight average molecular weight target value of 10,000. is there.
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, 129.1 parts of PGME 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 containing the following monomer mixture, solvent, and polymerization initiator was dropped from the dropping funnel into the flask at a constant dropping rate over 4 hours, and the temperature of 80 ° C. was further maintained for 3 hours. Seven hours after the start of dropping of the dropping solution, the reaction was stopped by cooling to room temperature.
25.95 parts (25 mol%) of monomer m-1;
26.87 parts (25 mol%) of monomer m-6,
39.65 parts (50 mol%) of monomer m-7,
92.5 parts ethyl lactate,
9.130 parts of dimethyl-2,2′-azobisisobutyrate (6.5 mol% based on the total amount of monomers supplied).

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

Next, the molecular weight of each monomer was used to convert the molar fraction of each monomer remaining in the flask at each sampling time (corresponding to Mx: My: Mz).
As a result, for example, the results after 3 hours and 4 hours after the start of dropping were as shown in Table 6.

In the same manner as in Reference Example 1, the content ratio (polymer composition) of the constituent units in the polymer produced in each reaction time zone was determined. The result is shown in FIG.
As shown in the results of FIG. 8, the polymer composition ratio (Px: Py: Pz) is the closest to the target composition 25:25:50, which was generated 3 to 4 hours after the start of dropping. The polymer was Px: Py: Pz = 24.32: 23.54: 46.86.
Using this value and the value of Mx: My: Mz (Table 6) after 3 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 = 1.30, Fy = 0.90, and Fz = 0.85. At this time, Fz is replaced with 0 from Fz <Fy <Fx.
The Sm composition x ₀ : y ₀ : z ₀ was determined using the factor value and the target composition.
x ₀ = 25 × Fx / (25 × Fx + 25 × Fy + 50 × Fz)
= 25 x 1.30 / (25 x 1.30 + 25 x 0.90 + 50 x 0) = 59.1 mol%.
y ₀ = 25 × Fy / (25 × Fx + 25 × Fy + 50 × Fz)
= 25 x 0.90 / (25 x 1.30 + 25 x 0.90 + 50 x 0) = 40.9 mol%.
z ₀ = 50 × Fz / (25 × Fx + 25 × Fy + 50 × Fz)
= 50 x 0 / (25 x 1.30 + 25 x 0.90 + 50 x 0) = 0 mol%.

<Example 5>
In this example, a post-process for dropping S2 was provided after the main process for dropping S1.
The composition of Sm obtained in Reference Example 3 was used as the composition of S2. 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 3. The monomer composition of S1 was the same as the target composition.
A flask equipped with a nitrogen inlet, a stirrer, a condenser, a dropping funnel, and a thermometer was charged with 123.3 parts of PGME 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, after dripping the whole amount of the following S1 into the flask over 4 hours from the dropping funnel, immediately dropping 80% by mass of the following S2 over 1 hour, and then adding the remaining 20% by mass over 1 hour. It was dropped and the temperature of 80 ° C. was further maintained for 1 hour. Seven hours after the start of dropping of the S1 solution, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S2 is 2.10% by mass of the total monomer supply amount.

(S1)
25.95 parts (25 mol%) of monomer m-1;
26.87 parts (25 mol%) of monomer m-6,
39.65 parts (50 mol%) of monomer m-7,
59.3 parts of PGME,
9.832 parts of dimethyl-2,2′-azobisisobutyrate (7 mol% based on the total amount of monomers in S1).
(S2)
1.25 parts (59.1 mol%) of monomer m-1;
0.73 part (40.9 mol%) of monomer m-6,
37.5 parts PGME,
0.162 parts of dimethyl-2,2′-azobisisobutyrate (7.0 mol% based on the total amount of monomers in S2).

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.
Comparing the results of FIG. 8 and FIG. 9, in Reference Example 3 (FIG. 8), the reaction time from 4 hours at the end of the main process (end of the dropping liquid) to the reaction time of 7 hours at the end of the holding process is increased. In the polymer produced in the meantime, the difference between the polymer composition ratio and the target composition increases with time.
On the other hand, in Example 5 (FIG. 9) in which a post-process for supplying S2 for a total of 2 hours after the end of the main process (end of dropping S1) was provided, after the end of the main process (reaction time 4 hours) The composition ratio of the polymer was very close to the target composition, and the variation in the composition ratio due to the reaction time was improved.

[Purification of polymer]
The 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 both changed to diisopropyl ether. In the same manner as in Example 1, a polymer P5 was obtained from the polymerization reaction solution in the flask after a reaction time of 7 hours had elapsed. Table 8 shows the results of Mw, Mw / Mn, and solubility evaluation of the polymer P5.

<Example 6>
In this example, S1 was supplied into the reactor in advance, and a post-process for dropping S3 was provided after the main process for dropping S2 and the polymerization initiator solution.
The composition of Sm obtained in Reference Example 3 was used as the composition of S3. 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 3. The monomer composition of S1 was the same as the first composition designed by the method using the above factors, and the monomer composition of S2 was the same as the target composition.
[Design of first composition of S1]
The first composition was determined using the factor values (Fx = 1.30, Fy = 0.90, Fz = 0.85) determined in Reference Example 3 and the target composition, and this was determined as the monomer composition of S1. It was.
_{x 00 = 25 / Fx = 25} / 1.30 = 19.2 mole%.
_{y 00 = 25 / Fy = 25} / 0.90 = 27.8 mole%.
_{z 00 = 50 / Fz = 50} / 0.85 = 58.8 mole%.
The following 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.
Then, supply of the following S2 and a polymerization initiator was started simultaneously from a separate dropping funnel, and S2 was dripped in a flask over 20 hours over 20 minutes. Further, immediately after the supply of S2, 80% by mass of S3 below was dropped over 1 hour, and then the remaining 20% by mass was dropped over 1 hour, and the temperature of 80 ° C. was maintained for 1 hour. Seven hours after the start of dropping of the solution of S2, the reaction was stopped by cooling to room temperature.
In this example, the total amount of monomers contained in S3 is 1.99% by mass of the total monomer supply amount.

(S1)
2.00 parts (18.2 mol%) of monomer m-1
2.99 parts (26.2 mol%) of monomer m-6,
4.74 parts (55.6 mol%) of monomer m-7,
139.0 parts of PGME.
(S2)
23.36 parts (25 mol%) of monomer m-1
24.19 parts (25 mol%) of monomer m-6,
39.57 parts (50 mol%) of monomer m-7,
44.5 parts PGME,
2.815 parts of dimethyl-2,2′-azobisisobutyrate (2.0 mol% based on the total amount of monomers in S1 and S2).
(Polymerization initiator solution)
5.2 parts ethyl lactate,
4.223 parts of dimethyl-2,2′-azobisisobutyrate (3.0 mol% based on the total amount of monomers in S1 and S2).
(S3)
1.25 parts (59.1 mol%) of monomer m-1;
0.73 part (40.9 mol%) of monomer m-6,
37.5 parts ethyl lactate,
0.132 parts of dimethyl-2,2′-azobisisobutyrate (5.0 mol% based on the total amount of monomers in S3).

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.
Compared to Reference Example 3 (FIG. 8), Example 6 (FIG. 10) is the end of the main process by providing a post-process for supplying S3 for a total of 2 hours after the end of the main process (end of dropping S2). Even after (reaction time 4 hours), the polymer composition ratio showed a value very close to the target composition, and the variation in composition ratio due to reaction time was improved.

[Purification of polymer]
In the same manner as in Example 5, polymer P6 was obtained from the polymerization reaction solution in the flask after 7 hours of reaction time. Table 8 shows the results of Mw, Mw / Mn, and solubility evaluation of the polymer P6.

<Comparative Examples 2-4>
In Reference Examples 1 to 3, after the reaction time of 7 hours had elapsed, the polymerization reaction solution in the flask obtained by cooling to room temperature and stopping the reaction was used, in the same manner as in the polymer purification step of Example 1. Comparative polymers were obtained respectively. About the obtained comparative polymer, it carried out similarly to Example 1, calculated | required Mw and Mw / Mn, and performed solubility evaluation. The results of Comparative Examples 2 and 3 are shown in Table 7, and the results of Comparative Example 4 are shown in Table 8.
In Comparative Examples 2 and 3, using the obtained comparative polymer, a resist composition was prepared in the same manner as in Example 1, and the sensitivity was evaluated. The results are shown in Table 7.

From the results of Table 7, the polymers obtained in Examples 1 and 2 are Comparative Example 1 (total amount of monomers contained in Sm dropped in the post-process: 15.67% by mass), Comparative Example 2 (post-process). Compared with the polymer obtained with the total amount of monomers contained in Sm dropped at 0% by mass), the solubility was remarkably improved, and the sensitivity when a resist composition was obtained was improved. Further, in Comparative Example 1 in which the total amount of monomers contained in the solution Sm dropped in the subsequent step was not appropriately controlled, the solubility was significantly reduced as compared with Example 1.
The polymers obtained in Examples 3 and 4 have significantly improved solubility as compared with the polymer obtained in Comparative Example 3 (total amount of monomers contained in Sm dropped in the subsequent step: 0% by mass). In addition, the sensitivity when using a resist composition was improved.

  From the results of Table 8, the polymers obtained in Examples 5 and 6 are respectively compared with the polymers obtained in Comparative Example 4 (total amount of monomers contained in Sm dropped in the subsequent step: 0% by mass). The solubility was significantly improved.

Claims (3)

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). A method for producing a lithographic polymer comprising:
Using a plurality of solutions S1 to Sm (m is 2 or 3) containing monomers and having different monomer compositions,
The polymerization step includes a main step of supplying the solutions S1 to S (m-1) into the reactor, respectively, and a post-step of supplying the solution Sm into the reactor after the main step is completed.
When m = 2, the monomer composition of the solution S1 in the main process is the same as the target composition,
Wherein when m = 3, the main monomer composition (unit: mol%) of the solution S1 in the step of _{α 11: α 12: ...:} α expressed in _1n, determined by the following procedure (1) - (3) F ₁ , F ₂ ,... F _n , α ₁₁ = α ′ ₁ / F ₁ , α ₁₂ = α ′ ₂ / F ₂ ,... Α _1n = α ′ _n / F _n , solution The monomer composition of S2 is the same as the target composition;
The total amount of monomers contained in the solution Sm is 0.1 to 10% by mass of the total monomer supply amount, and the solution Sm is the most copolymerization reaction among the monomers α _{1 to} α _n. Does not contain slow monomers,
In the subsequent step, the target composition (unit: mol%) representing the content ratio of the structural units α ′ _{1 to} α ′ _n in the polymer (P) is α ′ ₁ : α ′ ₂ :...: Α ′ _n The composition (unit: mol%) of the monomer contained in the solution Sm is represented by α _m1 : α _m2 :...: Α _mn , and the factor obtained by the following procedures (1) to (3) is F _1. , F ₂ ,... F _n ( _where the smallest of F _{1 to} F _n is replaced with 0), α _m1 = α ′ ₁ × F ₁ / (α ′ ₁ × F ₁ + α ′) ₂ × F ₂ +... + Α ′ _n × F _n ), α _m2 = α ′ ₂ × F ₂ / (α ′ ₁ × F ₁ + α ′ ₂ × F ₂ +... + Α ′ _n × F _n ) _{,. = α 'n × F n /} (α' 1 × F 1 + α '2 × F 2 + ... + α' n × F n) is a method for producing a lithographic polymer.
(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 r} until _{t r + 1} (r is 1 or more Find an integer.)
(3) _P in the "during the period from _{t r} to _{t r + 1" 1:} P _{2: ...:} and the value of _{P n, M} in the elapsed time _{t r 1: M 2: ...} : from the value of _{M n,} the following 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 . A step of producing a polymer for lithography by the method for producing a polymer for lithography according to claim 1 and a step of mixing the obtained polymer for lithography and a compound that generates an acid upon irradiation with actinic rays or radiation. A method for producing a resist composition. A step of producing a resist composition by the method for producing a resist composition according to claim 2 , a step of applying the obtained resist composition onto a work surface of a substrate to form a resist film, and the resist The manufacturing method of the board | substrate with which the pattern was formed including the process of exposing with respect to a film | membrane, and the process of developing the exposed resist film using a developing solution.

Images