JP6439278B2 - Lithographic polymer manufacturing method, resist composition manufacturing method, and pattern-formed substrate manufacturing method - Google Patents

Description

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

  In recent years, a resist pattern formed in a manufacturing process of a semiconductor element, a liquid crystal element, or the like has been rapidly miniaturized due to progress in lithography technology. 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. .

  For example, as a chemically amplified resist polymer used in ArF excimer laser lithography, an acrylic polymer that is transparent with respect to light having a wavelength of 193 nm has attracted attention. As the acrylic polymer, for example, a polymer of (meth) acrylic acid ester having an adamantane skeleton in an ester portion and (meth) acrylic acid ester having a lactone skeleton in an ester portion has been proposed (Patent Document 1). etc).

  In Patent Document 2, a very small amount of an ultrahigh molecular weight component generated in the polymerization process causes a decrease in the solubility of a lithography polymer in a resist solvent or a decrease in the solubility in alkali developability. As a result, it is described that the sensitivity of the resist composition is lowered. Further, it is described that if the ratio of monomer units constituting the copolymer (copolymerization composition) varies, the solubility in a solvent tends to be low, and the sensitivity of the resulting resist composition tends to be insufficient. ing. Thus, in order to obtain a fine resist pattern profile by making the resist pattern finer, it is necessary to improve the solubility of the polymer for lithography in the solvent and improve the sensitivity of the resist composition. This manufacturing method is not necessarily sufficient.

JP 10-319595 A International Publication No. 2011/004840

  The present invention has been made in view of the above circumstances, and can improve the solubility of a lithographic polymer in a solvent, and can improve sensitivity when used in a resist composition. It is intended to provide a method for producing a resist composition using a lithography polymer obtained by the production method, and a method for producing a substrate on which a pattern is formed using the resist composition. And

The above problems are solved by the present inventions [1] to [10] below.
[1] To obtain a polymerization reaction solution by radical polymerization of a monomer using a polymerization initiator in the presence of a polymerization solvent in a state where the oxygen concentration in the gas phase of the reaction vessel is less than 3.0 vol%. A polymerization step comprising:
A stopping step of stopping the polymerization reaction of the obtained polymerization reaction solution;
Substitution step of substituting the gas phase of the container of the polymerization reaction solution with a gas containing 3.0 vol% or more oxygen after the stopping step,
A method for producing a polymer for lithography, comprising:
[2] The method for producing a polymer for lithography according to claim 1, wherein the polymerization reaction solution is cooled in the stopping step.
[3] The method for producing a polymer for lithography according to claim 1 or 2, further comprising a step of performing reprecipitation purification of the polymerization reaction solution after the substitution step.
[4] The method for producing a polymer for lithography according to any one of [1] to [3], wherein the container in the substitution step is a reaction vessel used in the polymerization step.
[5] After the stopping step, a step of filling a container different from the reaction vessel used in the polymerization step, and a replacement step of replacing the gas phase of the filled vessel with a gas containing 3.0 vol% or more oxygen. The method for producing a polymer for lithography according to any one of [1] to [3].
[6] The method for producing a polymer for lithography according to any one of [1] to [3], further comprising a step of storing the polymerization reaction solution after the substitution step and before the step of performing reprecipitation purification.
[7] The method for producing a polymer for lithography according to [6], wherein the temperature of the polymerization reaction solution in the storing step is 30 ° C. or lower. [8] The gas containing 3.0 vol% or more of oxygen is 3 The method for producing a lithographic polymer according to any one of [1] to [7], which contains oxygen of not less than 0.0 vol% and not more than 22.0 vol%. [9] The method according to any one of [1] to [8] A method for producing a resist composition comprising mixing a polymer for lithography obtained by a method for producing a polymer and a compound capable of generating an acid upon irradiation with actinic rays or radiation.
[10] A step of applying a resist composition obtained by the method for producing a resist composition according to [9] on a processed surface of a substrate to form a resist film, and exposing the resist film A method for producing a substrate on which a pattern is formed, comprising: a step; and a step of developing the exposed resist film with a developer.

According to the method for producing a polymer for lithography of the present invention, the polymer for lithography capable of improving the solubility of the polymer for lithography in a solvent and improving the sensitivity when used in a resist composition. Is obtained.
According to the method for producing a resist composition of the present invention, a resist composition excellent in sensitivity can be obtained, which includes the lithography polymer produced by the production method of the present invention.
According to the substrate manufacturing method of the present invention, a highly accurate fine resist pattern can be stably formed using a resist composition having excellent sensitivity.

In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid, and “(meth) acryloyloxy” means acryloyloxy or methacryloyloxy.
<Polymer for lithography>
The polymer for lithography in the present invention (hereinafter sometimes simply referred to as polymer or polymer (P)) is not particularly limited as long as it is a polymer used in the lithography process. For example, a resist polymer used for forming a resist film, an antireflection film (TARC) formed on the upper layer of the resist film, or a reflection used for forming an antireflection film (BARC) formed on the lower layer of the resist film. Examples thereof include a polymer for prevention film, a gap fill film polymer used for forming a gap fill film, and a polymer for top coat film used for forming a top coat film.

Examples of the resist polymer include a copolymer containing at least one structural unit having an acid leaving group and at least one structural unit having a polar group.
Examples of the polymer for antireflection film include a structural unit having a light-absorbing group and an amino group, an amide group, a hydroxyl group, an epoxy group, etc. that can be cured by reacting with a curing agent to avoid mixing with the resist film. And a copolymer containing a structural unit having a reactive functional 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. Among these, those having a protected or unprotected phenolic hydroxyl group as the light absorbing group are preferable from the viewpoint of good developability and high resolution. Examples of the structural unit / monomer having the light-absorbing group include benzyl (meth) acrylate and p-hydroxyphenyl (meth) acrylate.

Examples of polymers for gap fill films are reactive functionalities that have a suitable viscosity for flowing into narrow gaps and can be cured by reacting with curing agents to avoid mixing with resist films and antireflection films. Examples thereof include a copolymer containing a structural unit having a group, specifically, a copolymer of hydroxystyrene and a monomer such as styrene, alkyl (meth) acrylate, or 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.

Hereinafter, the structural unit and the monomer corresponding thereto that are suitably used when the lithography polymer is a resist polymer will be described.
[Structural unit having a polar group]
The resist polymer preferably has a structural unit 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.
In the case where the polymer contains a structural unit having a lactone skeleton, the content thereof is preferably 20 mol% or more, more preferably 25 mol% or more of all structural units (100 mol%) from the viewpoint of adhesion to a substrate or the like. Is more preferable. Moreover, from the point of a sensitivity and resolution, 60 mol% or less is preferable, 55 mol% or less is more preferable, and 50 mol% or less is 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]} cited decan-3-one and the like . Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
Monomers having a lactone skeleton may be used alone or in combination of two or more.

(Structural unit / monomer having a hydrophilic group)
The “hydrophilic group” in the present specification is at least one of —C (CF ₃ ) ₂ —OH, 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 polymer is preferably from 5 to 30 mol%, more preferably from 10 to 25 mol%, of the total structural units (100 mol%) from the viewpoint of the resist pattern rectangularity. .

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

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

[Constitutional unit having acid leaving group]
The resist polymer preferably has a structural unit having an acid-leaving group in addition to the above-described structural unit having a polar group for use in resist applications. In addition to this, a known structural unit may be added if necessary. You may have.
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.
As the monomer having an acid leaving group, one type may be used alone, or two or more types may be used in combination.

<Polymerization solvent>
Examples of the polymerization solvent used in the present invention include the following.
Ethers: chain ether (diethyl ether, propylene glycol monomethyl ether (hereinafter referred to as “PGME”), etc.), cyclic ether (tetrahydrofuran (hereinafter referred to as “THF”), 1,4-dioxane, etc. )etc.
Esters: methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”), γ-butyrolactone, and the like.
Ketones: acetone, methyl ethyl ketone (hereinafter referred to as “MEK”), methyl isobutyl ketone (hereinafter referred to as “MIBK”), cyclohexanone, 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.
An organic solvent may be used individually by 1 type, and may use 2 or more types together.

<Polymerization initiator>
The polymerization initiator used in the present invention is preferably one that generates radicals efficiently by heat. For example, an azo compound (2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] Etc.), organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc.) and the like.
The suitability temperature of these polymerization initiators depending on the decomposition temperature is in the range of 50 to 150 ° C.

<Method for producing polymer>
In the present invention, as the polymerization method, a solution polymerization method is used in which a monomer is radically polymerized using a polymerization initiator in the presence of a polymerization solvent.
That is, the method for producing a polymer of the present invention comprises a polymerization step of radically polymerizing a monomer using a polymerization initiator in the presence of a polymerization solvent to obtain a polymerization reaction solution containing the produced polymer (P). And a stopping step for stopping the polymerization reaction of the obtained polymerization reaction solution, and a storage step for storing the polymerization reaction solution after the reaction is stopped.

[Polymerization process]
In the polymerization step, a polymerization solvent, a polymerization initiator, and a monomer are supplied into a polymerization vessel, and a radical polymerization reaction is performed while maintaining a predetermined polymerization temperature.
The supply of the monomer and the polymerization initiator to the polymerization vessel may be a continuous supply or a drop supply. A drop polymerization method in which a monomer and a polymerization initiator are dropped into a polymerization vessel is preferred because variations in average molecular weight and molecular weight distribution due to differences in production lots are small and a reproducible polymer can be easily obtained.

In the dropping polymerization method, the inside of the polymerization vessel is heated to a predetermined polymerization temperature, and then the monomer and the polymerization initiator are dropped into the polymerization vessel independently or in any combination.
A monomer may be dripped only with a monomer, and may be dripped as a monomer solution which melt | dissolved the monomer in the polymerization solvent.
A polymerization solvent and / or monomer may be charged into the polymerization vessel in advance.
The polymerization initiator may be dissolved directly in the monomer, may be dissolved in the monomer solution, or may be dissolved only in the polymerization solvent.
The monomer and the polymerization initiator may be dropped into the polymerization vessel after mixing in the same storage tank; they may be dropped into the polymerization container from each independent storage tank; They may be mixed immediately before the supply and dropped into the polymerization vessel.
One of the monomer and the polymerization initiator may be dropped first, and then the other may be dropped with a delay, or both may be dropped at the same timing.
The dropping rate may be constant until the end of dropping, or may be changed in multiple stages according to the consumption rate of the monomer or the polymerization initiator.
The dripping may be performed continuously or intermittently.
The polymerization temperature is preferably set within the range of the suitability temperature for the polymerization initiator. For example, 50-150 degreeC is preferable.

In the solution polymerization method, the viscosity of the reaction solution in which the polymerization reaction is performed increases as the monomer polymerization reaction proceeds. If the viscosity of the reaction solution becomes too high, a so-called runaway reaction may occur in which the polymerization reaction proceeds rapidly.
In the present specification, a reaction solution in which a monomer is subjected to a polymerization reaction using a polymerization initiator in the presence of a polymerization solvent is referred to as a polymerization reaction solution. The polymerization reaction solution contains the polymer (P) produced by the polymerization reaction.
The viscosity of the polymerization reaction solution decreases when the amount of the polymerization solvent used in the polymerization reaction is large, and increases when the amount of the polymerization solvent used is small. The amount of the polymerization solvent used for the polymerization reaction may be set so that the viscosity of the reaction solution is low enough to prevent the above-mentioned runaway reaction, and the production amount becomes worse as the amount of the polymerization solvent used increases.
The viscosity of the polymerization reaction solution can be adjusted to an arbitrary viscosity by diluting with a solvent. Specific examples of the dilution solvent include 1,4-dioxane, acetone, THF, MEK, cyclopentanone, cyclohexanone, MIBK, γ-butyrolactone, PGMEA, PGME, ethyl lactate, methyl 2-hydroxyisobutyrate, methanol, ethanol, isopropyl Examples thereof include alcohol, water, hexane, heptane, diisopropyl ether, and mixed solvents thereof.
The viscosity at 25 ° C. of the polymerization reaction solution is preferably 25 mPa · s or more from the viewpoint of production efficiency, more preferably 50 mPa · s or more, 100 mPa · s or more, and particularly preferably 150 mPa · s or more. The upper limit of the viscosity of the polymerization reaction solution is not limited as long as the runaway reaction does not occur, and is preferably 10,000 mPa · s or less, and more preferably 9,000 mPa · s or less.
Dilution with a solvent can be performed during the polymerization step, and can also be performed during the stop step described below.

[Stop process]
In the polymerization step, a radical polymerization reaction is performed while maintaining a predetermined polymerization temperature for a preset polymerization time, and then the polymerization reaction of the obtained polymerization reaction solution is stopped.
The radical polymerization reaction proceeds in a chain mechanism consisting of four elementary reactions: initiation reaction, growth reaction, termination reaction, and chain transfer reaction. The molecular weight of the polymer (P) produced depends on the speed and mechanism of each elementary reaction. It is decided. The growth reaction rate is proportional to the product of the monomer concentration and the radical concentration, and the termination reaction is proportional to the square of the radical concentration.
In the present invention, “stopping the polymerization reaction” means that the amount of radicals generated by the decomposition of the polymerization initiator is sufficiently reduced so as not to cause an initiation reaction and a growth reaction.
As a method for stopping the polymerization reaction, a process of cooling the reaction solution is generally used, but it can also be stopped by adding a radical scavenger.

[Replacement process]
After the stopping step, the gas phase of the polymerization reaction solution container is replaced with a gas containing 3.0 vol% or more of oxygen.
Unreacted monomers and polymerization initiators remain in the polymerization reaction solution once the polymerization reaction has been stopped in the stopping step, and the reactivation of the polymerization reaction from radicals generated from the polymerization initiator is suppressed. It is possible to suppress the generation of a polymer having a high molecular weight or a copolymer composition that is biased during storage, and it is possible to suppress the quality deterioration of the polymerization reaction solution during storage. In particular, the effect of the present invention can be obtained when the storage period is 5 hours or more.

[Storage process]
In the preservation | save process of this invention, the polymerization reaction solution after reaction stop is maintained in the state which contacted the gas containing 3.0 vol% or more oxygen. The preservation is to keep the state as it is, and in the preservation step of the present invention, the polymerization reaction solution after the stopping step is kept in a solution state, for example, it is kept for 1 hour or more.
Unreacted monomers and polymerization initiator remain in the polymerization reaction solution once the polymerization reaction is stopped in the stopping step, and kept in contact with a gas containing 3.0 vol% or more oxygen. For example, even when the polymerization reaction solution is stored for a long period of time of 1 hour or longer, the reinitiation of the polymerization reaction from radicals generated from the polymerization initiator can be suppressed. It is possible to suppress the formation of a polymer having a biased polymerization composition and to suppress the deterioration of the quality of the polymerization reaction solution during storage. In particular, the effect of the present invention can be obtained when the storage period is 5 hours or more.
As a method of keeping the polymerization reaction solution in contact with a gas containing oxygen of 3.0 vol% or more, a method of introducing a gas containing 3.0 vol% or more of oxygen into the gas portion of the polymerization vessel, After transferring the polymerization reaction solution to another storage container, the surface of the polymerization reaction solution may be stored in contact with a gas containing 3.0 vol% or more oxygen.
In the present invention, oxygen gas or air (oxygen concentration of 3.0 vol% or more and 22 vol% or less) can be used as the gas containing oxygen of 3.0 vol% or more. It is preferable to use air from the viewpoint of workability and the like.
In particular, the effect of the present invention can be achieved when the amount of residual monomer in the polymerization reaction solution after the stopping step is large. Specifically, when 5 mol% or more of the monomer supply amount of the total monomer remains, further when 10 mol% or more of the monomer remains, particularly 15 mol% or more of the single monomer supply amount. A remarkable effect is obtained when the polymer remains.
In the preservation | save process of this invention, what is necessary is just to be kept in the solution state in the state which contacted the gas containing 3.0 vol% or more oxygen. The storage temperature can be any temperature, but is preferably stored at 30 ° C. or less, more preferably 25 ° C. or less, and preferably 20 ° C. or less in terms of effectively suppressing deterioration in quality due to thermal decomposition. Further preferred is 15 ° C. or less. Moreover, -20 degreeC or more is preferable at the point which is easy to preserve | save.
During storage of the polymerization reaction solution, the reaction solution can be stirred to maintain a uniform mixed state.
The container for storing the polymerization reaction solution may be in an open state or may be kept in a sealed state. Further, it is preferable to use a container having a light shielding state, for example, a transmittance of light of 500 nm or less is 10% or less.
In addition, after filling the container different from the reaction container used in the polymerization step, the gas phase of the filled container may be replaced with a gas containing 3.0 vol% or more oxygen.

[Reprecipitation process]
In the method for producing a polymer of the present invention, the polymerization reaction solution obtained through the storage step may be mixed with a poor solvent (preferably dropped in the poor solvent) to precipitate the polymer in the polymerization reaction solution. Good. This step is called reprecipitation and is very effective for removing impurities such as unreacted monomers and polymerization initiator remaining in the polymer solution. If the unreacted monomer remains as it is, the sensitivity decreases when used as a resist composition, so it is preferable to remove it as much as possible.
The amount of the poor solvent at the time of dropping the diluted solution into the poor solvent is not particularly limited, but is preferably equal to or more than that of the diluted solution in terms of easier reduction of unreacted monomers, and 3 on a mass basis. Is preferably 4 times or more, more preferably 4 times or more, still more preferably 5 times or more, and particularly preferably 6 times or more. The upper limit is preferably 10 times or less on a mass basis from the viewpoint that the amount of the poor solvent used is not too large and productivity is not lowered.

  Then, the target polymer is obtained in the state of a wet powder by filtering the deposit in a poor solvent. The smaller the monomer content in the polymer, the better.

[Post-process]
By drying the wet powder obtained by filtering the precipitate in the poor solvent, a dry powder of the target polymer can be obtained.
Alternatively, the operation of separating the filter after the filtered wet powder is again dispersed in a poor solvent to obtain a polymer dispersion can be repeated. This step is called a restructuring step and is effective for further reducing impurities such as unreacted monomers and polymerization initiator remaining in the polymer wet powder.
From the viewpoint that the polymer can be obtained while maintaining high productivity, it is preferable to perform the purification only by the reprecipitation step without performing the restructuring step.

Further, the wet powder may be used as a lithography composition by dissolving it in a suitable solvent without drying and may be used as a lithography composition after concentration to remove low boiling point compounds. Good. At that time, additives such as a storage stabilizer may be appropriately added.
Alternatively, the moist powder may be dried and then dissolved in an appropriate solvent, and further concentrated to remove the low boiling point compound, and then used as a lithography composition. At that time, additives such as a storage stabilizer may be added as appropriate.

<Method for producing resist composition>
The polymer thus obtained and a compound that generates an acid upon irradiation with actinic rays or radiation are mixed to produce a resist composition. The resist composition is a chemically amplified resist composition. Preferably, the polymer and a compound capable of generating an acid upon irradiation with actinic rays or radiation are dissolved in a resist solvent.

[Resist solvent]
As the resist solvent, the solvents listed above as the polymerization solvent can be used.
[Compound that generates acid upon irradiation with actinic ray or radiation]
The compound that generates an acid upon irradiation with actinic rays or radiation can be arbitrarily selected from those that can be used as a photoacid generator for a 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 the usage-amount of a photo-acid generator, 0.5-10 mass parts is more preferable.

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

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

[Additive]
The resist composition 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 fine pattern is formed>
An example of the manufacturing method of the board | substrate with which the fine pattern was formed of this invention is demonstrated.
First, the resist composition obtained by the production method of the present invention is applied to the surface of a substrate to be processed such as a silicon wafer on which a desired fine pattern is to be formed by spin coating or the like. And the resist film is formed on a board | substrate by drying the to-be-processed board | substrate with which this resist composition was apply | coated by baking process (prebaking) etc.

Next, the resist film is irradiated with light having a wavelength of 250 nm or less through a photomask to form a latent image (exposure). As irradiation light, a KrF excimer laser, an ArF excimer laser, an F ₂ excimer laser, and an EUV excimer laser are preferable, and an ArF excimer laser is particularly preferable. Moreover, you may irradiate an electron beam.
In addition, immersion in which light is irradiated with a high refractive index liquid such as pure water, perfluoro-2-butyltetrahydrofuran, or perfluorotrialkylamine interposed between the resist film and the final lens of the exposure apparatus. Exposure may be performed.

After the exposure, heat treatment is appropriately performed (post-exposure baking, PEB), an alkali developer is brought into contact with the resist film, and the exposed portion is dissolved in the developer and removed (development). 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 to be processed.

The substrate on which the resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist and selectively etch the portion without the resist.
After the etching, the resist is removed with a release agent to obtain a substrate on which a fine pattern is formed.

According to the present invention, as shown in the examples described later, a lithographic polymer having excellent solubility in a solvent and good sensitivity when used in a resist composition can be obtained.
This is because, in the storage step, the polymer reaction solution is kept in a solution state in contact with a gas containing oxygen of 3.0 vol% or more, so that a polymer having a high molecular weight or a copolymer composition biased during storage can be obtained. It is thought that it was reduced.

  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: 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.
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).

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 solubility>
20 parts of the polymer and 80 parts of PGMEA were mixed, stirred while being kept at 25 ° C., and the time until complete dissolution determined by visual observation was measured.

<Quantification of monomer in reaction solution>
0.5 g of the reaction solution in the reaction vessel after the stopping step 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 unreacted monomer content in the diluted solution was determined by using a high performance liquid chromatograph HPLC-8020 (product name) manufactured by Tosoh Corporation. Asked for each body. The molar ratio (mol%) of the total monomer amount in the reaction solution was defined as the content of the monomer remaining in the reaction solution. Below the lower limit of detection, the residual monomer amount was 0 mol%.

In the measurement by the high performance liquid chromatograph, the separation column uses one Inertsil ODS-2 (trade name) manufactured by GL Sciences, the mobile phase is a water / acetonitrile gradient system, the flow rate is 0.8 mL / min, the detector. Was measured with an ultraviolet / visible absorptiometer UV-8020 (trade name) manufactured by Tosoh Corporation, a detection wavelength of 220 nm, a measurement temperature of 40 ° C., and an injection amount of 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 monomer content, 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 resist composition>
[Sensitivity and development contrast measurement]
The resist composition was spin-coated on a 6-inch silicon wafer and prebaked (PAB) at 120 ° C. for 60 seconds on a hot plate to form a thin film having a thickness of 300 nm. Using an ArF excimer laser exposure apparatus (product name: VUVES-4500, manufactured by RISOTEC Japan), 18 shots of 10 mm × 10 mm ² were exposed while changing the exposure amount. Then, after post-baking (PEB) at 110 ° C. for 60 seconds, 2.38 mass% tetramethylammonium hydroxide at 23 ° C. using a resist development analyzer (product name: RDA-800). Development was performed with an aqueous solution for 65 seconds, and the change with time in the resist film thickness during development at each exposure amount was measured.

[analysis]
A curve plotting the logarithm of the exposure amount (mJ / cm ² ) and the residual film thickness ratio (hereinafter referred to as the residual film ratio) (%) when developed for 60 seconds with respect to the initial film thickness, based on the obtained data (Hereinafter, exposure amount-residual film rate curve) was prepared, and Eth sensitivity (required exposure amount for setting the residual film rate to 0%, which represents sensitivity) was determined as follows. It shows that the sensitivity of a resist composition is so high that the value of Eth sensitivity is small.
Eth sensitivity: exposure amount (mJ / cm ² ) at which the exposure amount-residual film rate curve intersects with a residual film rate of 0%.

<Example 1>
111.1 g of PGMEA was put into a 1 L capacity SUS flask equipped with a nitrogen inlet, a stirrer, a condenser, one dropping funnel, and a thermometer. The inside of the flask was replaced with nitrogen, the flask was placed in a hot water bath while maintaining the nitrogen atmosphere, the temperature of the hot water bath was raised while stirring the inside of the flask, and the temperature of the liquid in the flask was raised to 80 ° C.
Thereafter, the following mixture 1 was dropped into the flask over 4 hours from the dropping funnel, and after maintaining the temperature of 80 ° C. for 3 hours, the heating of the hot water bath was stopped, and the hot water in the hot water bath was changed to 20 ° C. water. By continuously replacing the flask, the polymerization reaction was stopped by cooling the flask.
[Mixture 1]
51.00 g (30 mol%) of a monomer of the following formula (m1),
124.00 g (50 mol%) of a monomer of the following formula (m2),
47.20 g (20 mol%) of a monomer of the following formula (m3),
PGMEA 222.2g,
11.500 g of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).

  When the polymerization reaction solution reached 25 ° C., a mixed gas of nitrogen (97 vol%) / oxygen (3 vol%) was supplied from the nitrogen inlet, so that the oxygen concentration in the gas phase portion in the flask was 3 vol% oxygen. Thereafter, the polymerization reaction solution was stored at 20 ° C. for 6 hours.

The obtained post-storage solution was dropped into a 10-fold amount (volume basis, the same shall apply hereinafter) of the poor solvent with stirring to precipitate a polymer (white precipitate). Methanol was used as the poor solvent.
The precipitate was filtered off to obtain a polymer wet powder. The polymer wet powder was dried under reduced pressure at 40 ° C. for about 40 hours to obtain a dry powder of the polymer.
The quantity of the monomer in the obtained reaction liquid was quantified. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer were measured. The solubility of the polymer was evaluated. The results are shown in Table 1.

[Evaluation of resist composition]
100 parts of the obtained polymer, 2 parts of triphenylsulfonium triflate as a photoacid generator, and PGMEA as a solvent were mixed uniformly so that the polymer concentration was 12.5% by mass. After preparing the solution, it was filtered through a membrane filter having a pore size of 0.1 μm to obtain a resist composition. Eth sensitivity was measured about the obtained resist composition. The results are shown in Table 1.

<Example 2>
In this example, a monomer of the following formula (m4) was used in place of the monomer of the formula (m2) in Example 1.
That is, 114.6 g of PGMEA was put in the same flask as in Example 1. The inside of the flask was replaced with nitrogen, the flask was placed in a hot water bath while maintaining the nitrogen atmosphere, the temperature of the hot water bath was raised while stirring the inside of the flask, and the temperature of the liquid in the flask was raised to 80 ° C.
Thereafter, the following mixture 2 was dropped from the dropping funnel into the flask over 4 hours, and further maintained at a temperature of 80 ° C. for 3 hours, and then cooled in the same manner as in Example 1.
[Mixture 2]
51.00 g (30 mol%) of a monomer of the following formula (m1),
131.00 g (50 mol%) of a monomer of the following formula (m4),
47.20 g (20 mol%) of a monomer of the following formula (m3),
PGMEA 229.2g,
11.500 g of dimethyl-2,2′-azobisisobutyrate (Wako Pure Chemical Industries, V601 (trade name)).

  When the polymerization reaction solution reached 25 ° C., a mixed gas of nitrogen (95 vol%) / oxygen (5 vol%) was supplied from the nitrogen inlet, so that the oxygen concentration in the air layer portion in the flask was 5 vol% oxygen. Thereafter, the polymerization reaction solution was stored at 25 ° C. for 8 hours.

  Thereafter, a polymer was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Example 3>

<Comparative Example 1>
A polymer was produced in the same manner as in Example 1 except that a nitrogen (97 vol%) / oxygen (3 vol%) mixed gas was not supplied into the flask in the storage step, but was stored in a nitrogen atmosphere at 20 ° C. for 6 hours. Made and evaluated. The results are shown in Table 1.
<Comparative Example 2>
Example 2 except that a nitrogen (99 vol%) / oxygen (1 vol%) mixed gas was supplied into the flask in the preservation step, and the oxygen concentration of the gas phase in the flask was 1 vol% oxygen and preserved at 25 ° C. for 8 hours. Polymers were produced and evaluated in the same manner as described above. The results are shown in Table 1.
<Comparative Example 3>

As shown in the results of Table 1, although the composition of the monomers used in Example 1 and Comparative Example 1 is the same, the gas containing oxygen of 3.0 vol% or more in the polymerization reaction solution after the reaction was stopped (Example 1), when the polymerization reaction solution after the reaction was stopped was kept in contact with a gas containing 0 vol% oxygen (Comparative Example 1), the average molecular weight ( Mw) is low. Similarly, although the compositions of the monomers used in Example 2 and Comparative Example 2 were the same, the polymerization reaction solution after the reaction was stopped was kept in contact with a gas containing 3.0 vol% or more oxygen. In the case (Example 2), the average molecular weight (Mw) is lower than that in the case where the polymerization reaction solution after stopping the reaction is kept in contact with a gas containing 1.0 vol% oxygen (Comparative Example 2).
From these results, it can be seen that the polymers obtained in Examples 1 and 2 are reduced in the amount of high molecular weight products produced during the storage process compared to the polymers obtained in Comparative Examples 1 and 2. .
In addition, the polymers obtained in Examples 1 and 2 are excellent in solubility in a solvent and excellent in sensitivity when used in a resist composition. The polymers obtained in Comparative Examples 1 and 2 were not completely dissolved in PGMEA and could not be evaluated as resist compositions. From these facts, the polymers obtained in Examples 1 and 2 were compared with the polymers obtained in Comparative Examples 1 and 2 to produce a polymer having a high molecular weight and a copolymer composition biased during the storage process. It is estimated that the amount is reduced.

Claims (9)

Polymerization including obtaining a polymerization reaction solution by radical polymerization of a monomer using a polymerization initiator in the presence of a polymerization solvent in a state where the gas phase oxygen concentration in the reaction vessel is less than 3.0 vol%. Process,
A stopping step of stopping the polymerization reaction of the obtained polymerization reaction solution;
After the stop process, the gas phase of the container of the polymerization reaction solution, and the replacement step of replacing with a gas containing oxygen above 3.0vol%,
A method for producing a polymer for lithography , comprising a step of reprecipitation purification of a polymerization reaction solution after the substitution step . The method for producing a polymer for lithography according to claim 1, wherein the polymerization reaction solution is cooled in the stopping step. The manufacturing method of the polymer for lithography of Claim 1 or 2 whose container of the said substitution process is the reaction container used at the superposition | polymerization process. After the stop step, the step of filling the polymerization reaction solution into a container different from the reaction vessel used in the polymerization step, and the gas phase of the filled vessel is replaced with a gas containing 3.0 vol% or more oxygen. The method for producing a polymer for lithography according to claim 1, further comprising a substitution step. The method for producing a polymer for lithography according to any one of claims 1 to 4 , further comprising a step of storing the polymerization reaction solution before the step of performing reprecipitation purification after the substitution step. The method for producing a polymer for lithography according to claim 5 , wherein the temperature of the polymerization reaction solution in the storing step is 30 ° C or lower. The method for producing a lithographic polymer according to any one of claims 1 to 6 , wherein the gas containing 3.0 vol% or more oxygen contains 3.0 vol% or more and 22.0 vol% or less oxygen. The process according to claim 1 and for lithography polymer obtained by the production method of the polymer according to any one of 7, the resist composition of mixing a compound which generates an acid upon irradiation with actinic rays or radiation. Applying the resist composition obtained by the method for producing a resist composition according to claim 8 on a work surface of a substrate to form a resist film, exposing the resist film, And a step of developing the exposed resist film using a developing solution.