JP5793825B2 - Lithographic polymer manufacturing method, resist composition manufacturing method, and substrate manufacturing method - Google Patents

Description

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

In the manufacturing process of semiconductor elements, liquid crystal elements, etc., in recent years, pattern formation by lithography has been rapidly miniaturized. As a technique for miniaturization, there is a reduction in wavelength of irradiation light.
Recently, KrF excimer laser (wavelength: 248 nm) lithography technology has been introduced, and ArF excimer laser (wavelength: 193 nm) lithography technology and EUV excimer laser (wavelength: 13 nm) lithography technology for further shortening the wavelength have been studied. .
Further, for example, as a resist composition that can suitably cope with a shorter wavelength of irradiation light and a finer pattern, a polymer in which an acid-eliminable group is eliminated by the action of an acid and becomes alkali-soluble, and a photoacid generator A so-called chemically amplified resist composition containing the above has been proposed, and its development and improvement are underway.

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

With the miniaturization of resist patterns, the demands on the quality of lithography polymers are becoming stricter. For example, a very small amount of high molecular weight component (high polymer) generated in the polymerization process causes a decrease in the solubility of the lithography polymer in the resist solvent and the solubility in the alkali developer, resulting in the sensitivity of the resist composition. Decreases.
In the following Patent Document 2, as a method for suppressing the formation of such a high polymer, a solution containing a polymerizable monomer and a solution containing a polymerization initiator are respectively held in independent storage tanks, and are continuously or There has been proposed a method of intermittent supply and radical copolymerization.

JP 2002-145955 A JP 2004-269855 A

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

In order to solve the above problems, a first aspect of the present invention is a method for producing a lithography polymer used for producing a resist composition, wherein a monomer and a polymerization initiator are supplied into a reactor. while, have a step of generating a polymer in the reactor, said a monomer monomer having an ethylenic double bond, wherein the polymerization initiator is a radical polymerization initiator, the monomer When 12.5% by mass of the total supply amount of the polymerization initiator is supplied into the reactor, 25% by mass or more of the total supply amount of the polymerization initiator is supplied into the reactor. A method for producing a polymer for lithography characterized in that a part of a polymerization initiator is previously charged in a reactor and heated to a polymerization temperature, and then a polymerization initiator and a monomer are supplied. Excluding).

In the second aspect of the present invention, the supply rate of the monomer into the reactor is constant, and 12.5% of the total supply period in which the monomer is supplied into the reactor has elapsed. Then, 25% by mass or more of the total supply amount of the polymerization initiator is supplied into the reactor. The method for producing a lithography polymer according to the first aspect is characterized in that
A third aspect of the present invention is the method for producing a lithographic polymer according to the first aspect or the second aspect, wherein a supply rate of the polymerization initiator into the reactor has a change over time.
According to a fourth aspect of the present invention, there is provided the method for producing a polymer for lithography according to any one of the first to third aspects, wherein the supply of the monomer and the supply of the polymerization initiator are simultaneously started in the reactor. It is.

A fifth aspect of the present invention, the a process for producing a lithographic polymer by any of the manufacturing methods of the first to fourth embodiments, the resulting lithographic polymer, and irradiation with actinic rays or radiation Is a method for producing a resist composition, comprising a step of dissolving a compound generating an acid in a resist solvent.
According to a sixth aspect of the present invention, there is provided a step of producing a resist composition by the method for producing a resist composition according to the fifth aspect, and applying the obtained resist composition onto a work surface of a substrate to form a resist. A method for producing a substrate on which a pattern is formed, comprising a step of forming a film, a step of exposing the resist film, and a step of developing the exposed resist film using a developer.

According to the method for producing a polymer of the present invention, a polymer having good solubility in a solvent and high sensitivity when used in a resist composition can be obtained.
The polymer for lithography of the present invention has good solubility in a solvent, and high sensitivity can be obtained 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.

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>
The polymer produced by the method of the present invention is a polymer produced by radical polymerization using a polymerization initiator. It may be a homopolymer or a copolymer. The use of the polymer 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 constitutional unit of the polymer is not particularly limited. However, when the polymer is a resist polymer, it preferably has a constitutional unit having an acid-eliminable group. You may have well-known structural units, such as a structural unit which has frame | skeleton, and a structural unit which has a hydrophilic group.
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.

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.

<Monomer>
The monomer used in the present invention is a monomer corresponding to each structural unit of the polymer to be obtained. The monomer is preferably a compound having a vinyl group, and is preferably a monomer that easily undergoes radical polymerization.

Hereinafter, the structural unit and the monomer corresponding to it used suitably in the resist polymer will be described.
In particular, as a monomer used for the resist polymer, (meth) acrylic acid ester is more preferable because of high transparency to exposure light having a wavelength of 250 nm or less.
[Structural Unit / Monomer Having Acid Leaving Group]
The “acid leaving group” is a group having a bond that can be cleaved by an acid, and a part or all of the acid leaving group can be removed from the main chain of the resist polymer by cleavage of the bond. is there.
When used as a resist composition, a resist polymer containing a structural unit having an acid-eliminable group is soluble in an alkali by an acid, and has the effect of enabling the formation of a resist pattern.
In view of sensitivity and resolution, the content of the structural unit having an acid leaving group is preferably 20 mol% or more, more preferably 25 mol% or more, of all the structural units constituting the resist polymer. Moreover, 60 mol% or less is preferable from the point of the adhesiveness to a board | substrate etc., 55 mol% or less is more preferable, and 50 mol% or less is further more preferable.

  The monomer having an acid leaving group may be a compound having an acid leaving group and a polymerizable multiple bond, and known ones can be used. The polymerizable multiple bond is a multiple bond that is cleaved during the polymerization reaction to form a copolymer chain, and an ethylenic double bond is preferable.

Specific examples of the monomer having an acid leaving group include (meth) acrylic acid esters having an alicyclic hydrocarbon group having 6 to 20 carbon atoms and having an acid leaving group. It is done. The alicyclic hydrocarbon group may be directly bonded to an oxygen atom constituting an ester bond of (meth) acrylic acid ester, or may be bonded via a linking group such as an alkylene group.
The (meth) acrylic acid ester has an alicyclic hydrocarbon group having 6 to 20 carbon atoms, and a tertiary carbon atom at the bonding site with the oxygen atom constituting the ester bond of the (meth) acrylic acid ester. A (meth) acrylic acid ester having an alicyclic 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, and isopropyl adamantyl (meth) acrylate.
Among these, 2-methyl-2-adamantyl methacrylate (m2 in the example), 1-ethylcyclohexyl methacrylate (m4 in the example), 1-ethylcyclopentyl methacrylate (m7 in the example), isopropyl adamantyl methacrylate (in the example) m10) is more preferable.
As the monomer having an acid leaving group, one type may be used alone, or two or more types may be used in combination.

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

(Constitutional unit / monomer having a lactone skeleton)
Examples of the lactone skeleton include a lactone skeleton having about 4 to 20 members. The lactone skeleton may be a monocycle having only a lactone ring, or an aliphatic or aromatic carbocyclic or heterocyclic ring may be condensed with the lactone ring.
When the copolymer includes a structural unit having a lactone skeleton, the content thereof is preferably 20 mol% or more of all structural units (100 mol%) from the viewpoint of adhesion to a substrate and the like, and 35 mol%. The above is more preferable. Moreover, from the point of a sensitivity and resolution, 60 mol% or less is preferable, 55 mol% or less is more preferable, and 50 mol% or less is further more preferable.

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

Specific examples of the monomer having a lactone skeleton include β- (meth) acryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β- (meth) acryloyl. Oxy-γ-butyrolactone, β- (meth) acryloyloxy-β-methyl-γ-butyrolactone, α- (meth) acryloyloxy-γ-butyrolactone, 2- (1- (meth) acryloyloxy) ethyl-4-butanolide , (Meth) acrylic acid pantoyl lactone, 5- (meth) acryloyloxy-2,6-norbornanecarbolactone, 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decane-3 -One, 9-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one and the like. Examples of the monomer having a similar structure include methacryloyloxysuccinic anhydride.
Among these, α-methacryloyloxy-γ-butyrolactone (Example m1), α-acryloyloxy-γ-butyrolactone (Example m8), 5-methacryloyloxy-2,6-norbornanecarbolactone (Example) m5), 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one (m6 in Examples) is more preferable.
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.

  As the monomer having a hydrophilic group, for example, 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 (cyclohexyl (meth) acrylate, 1-isobornyl (meth) acrylate, adamantyl (meth) acrylate), tricyclodecanyl (meth) acrylate, dimethacrylate (meth) acrylate Cyclopentyl, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, etc.) having a hydrophilic group such as a hydroxy group or a carboxy group as a substituent. Can be mentioned.

Specific examples of the monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxy- (meth) acrylate. -Propyl, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate, etc. Is mentioned. From the viewpoint of adhesion to a substrate or the like, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate and the like are preferable.
Among these, 3-hydroxyadamantyl methacrylate (m3 in Examples) and 2-cyanomethyl-2-adamantyl methacrylate (m9 in Examples) are more preferable.
The monomer which has a hydrophilic group may be used individually by 1 type, and may be used in combination of 2 or more type.

<Polymerization initiator>
As the polymerization initiator, those that generate radicals efficiently by heat are preferable. For example, an azo compound (2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] Etc.), organic peroxides (2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, di (4-tert-butylcyclohexyl) peroxydicarbonate, etc.) and the like. An azo compound is more preferable.
The amount (total supply amount) of the polymerization initiator is set according to the type of the polymerization initiator and according to the target molecular weight of the polymer to be obtained. When the amount of the polymerization initiator used is large, the molecular weight of the resulting polymer decreases, and when the amount of the polymerization initiator used is small, the molecular weight of the resulting polymer tends to increase.
The range of the used amount (total supply amount) of the polymerization initiator is not particularly limited, but is in the range of 0.1 to 40.0 parts by mass with respect to 100 parts by mass of the total amount of monomers (total supply amount). The range of 0.3 to 30.0 parts by mass is more preferable.

<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: linear ethers (eg, diethyl ether, propylene glycol monomethyl ether, etc.), cyclic ethers (eg, tetrahydrofuran (hereinafter referred to as “THF”), 1,4-dioxane, etc.) and the like.
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, 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.

<Method for producing polymer>
The polymer of the present invention is produced by a radical polymerization method. The polymerization method is not particularly limited, but a solution polymerization method is preferable.
The method for producing a polymer of the present invention includes a step of producing a polymer in the reactor while supplying the monomer and the polymerization initiator into the reactor. Both the monomer and the polymerization initiator are preferably supplied in liquid form. The method for supplying the monomer and the polymerization initiator may be any method that can be gradually supplied into the reactor, and is preferably supplied dropwise. The supply may be continuous or intermittent. The supply rate may be constant or may change over time.

  Preferably, after the inside of the reactor is heated to a predetermined polymerization temperature, the monomer and the polymerization initiator are supplied into the reactor in a liquid state. The monomer may be supplied in a liquid state consisting of only the monomer, or a monomer solution in which the monomer is dissolved in a solvent may be supplied. As the monomer solution, one liquid containing all of the monomers to be used may be used, or two or more liquids each including a part of the monomers to be used may be used.

The polymerization initiator may be supplied in a liquid form dissolved in a liquid composed of a monomer, may be supplied in a liquid form dissolved in a monomer solution, or may be supplied in a liquid form dissolved only in a solvent. May be. All of the polymerization initiator to be used may be contained in one liquid, or may be supplied separately in two or more liquids.
When the monomer and the polymerization initiator are dissolved in the same liquid and supplied, they may be mixed in the same storage tank and then supplied into the reactor, immediately before being supplied from each independent storage tank to the reactor. May be mixed.

  The reactor may be charged with a solvent in advance or may not be charged. When the solvent is not charged to the reactor in advance, the monomer or the polymerization initiator is supplied into the reactor in the absence of the solvent. Preferably, the solvent is charged in the reactor in advance.

In the present invention, when 12.5% by mass of the total supply amount of the monomer is supplied into the reactor, 25% by mass or more of the total supply amount of the polymerization initiator is at least 25% by mass in the reactor. Control the supply as it is supplied in.
That is, if the monomer and the polymerization initiator are started to be supplied at the same time, the supply rate is kept constant, and the supply is completed at the same time, the supply ratio of the monomer and the polymerization initiator to the total supply amount is any time. Become the same. For example, when 12.5% by mass of the total supply amount of the monomer is supplied into the reactor, 12.5% by mass of the polymerization initiator is also supplied into the reactor. Yes. On the other hand, in the present invention, the supply amount of the polymerization initiator at the initial stage of the period in which the monomer is supplied is increased. That is, by the time when 12.5% by mass of the total monomer supply amount is supplied into the reactor, the amount of the polymerization initiator supplied into the reactor is equal to the total supply amount of the polymerization initiator. Is at least 25% by mass, preferably 50% by mass or more, and more preferably 70% by mass or more. It may be 100% by mass.

The monomer and the polymerization initiator may start supplying one after the other, then start supplying the other later, or both may start supplying at the same time. It is preferable to start supplying the initiator first. It is more preferable to start supplying both at the same time.
Moreover, it is preferable that the supply rates of the monomer and the polymerization initiator can be controlled separately. Therefore, it is preferable to use at least two liquids, a liquid containing part or all of the monomer and a liquid containing part or all of the polymerization initiator.
In order to stably produce the polymer, it is preferable that the monomer is continuously supplied and the supply rate is constant. On the other hand, it is preferable that the polymerization initiator is continuously supplied and the supply rate is changed stepwise. That is, immediately after the start of the supply of the polymerization initiator, the supply rate is high and constant, and after a predetermined amount is supplied, it is preferable to reduce the supply rate and supply at a constant rate. The period during which the supply rate is high immediately after the start of the supply of the polymerization initiator is from 1 to 30 minutes after the monomer is started to be supplied simultaneously with the polymerization initiator, or after the monomer is started to be supplied later than the polymerization initiator. It is preferable to finish by later.

  In the present invention, when the supply rate of the monomer into the reactor is constant, the above-mentioned time is reached when 12.5% of the total period during which the monomer is supplied into the reactor has elapsed. Similarly, it is sufficient that 25% by mass or more of the total supply amount of the polymerization initiator is supplied into the reactor. Also in this case, the supply rate of the polymerization initiator may be constant or may change with time.

According to the present invention, as shown in Examples and Comparative Examples described later, by the time when 12.5% by mass of the total monomer supply amount is supplied into the reactor, Comparative example in which the supply start and the supply end of the monomer and the polymerization initiator are simultaneous with each other and the supply speed is constant by supplying 25% by mass or more of the total supply amount into the reactor. Hereinafter, the solubility of the resulting polymer is improved and the sensitivity when a resist composition is obtained is improved as compared to “Comparative Example with the same supply ratio”.
That is, when the composition and amount of the monomer used and the amount of the polymerization initiator used are the same, the polymer obtained by the production method of the present invention has a smaller Mw than the comparative example in which the supply ratio is equal. Thus, the solubility is improved.
Further, by changing the amount of the polymerization initiator used, when the Mw of the comparative example having the same supply ratio is substantially equal to the Mw of the polymer obtained by the production method of the present invention, it is obtained by the production method of the present invention. The obtained polymer has higher solubility.
Therefore, according to the present invention, a polymer with improved solubility can be produced while having the same monomer composition and Mw as the conventional product. Furthermore, if the amount of the polymerization initiator used is adjusted, the Mw can be adjusted without changing the monomer composition, so that the desired monomer composition has the desired Mw and has excellent solubility. Combines can be manufactured.
The reason why such an effect can be obtained in the present invention is considered to be that the production of a high polymer is suppressed by increasing the supply amount of the polymerization initiator in the initial period of supplying the monomer.

<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. 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 high sensitivity.
Therefore, according to the substrate manufacturing method of the present invention, a highly accurate fine resist pattern can be stably formed by using the resist composition of the present invention. In addition, it is also suitable for pattern formation by photolithography using exposure light having a wavelength of 250 nm or less or lithography using electron beam lithography such as ArF excimer laser (193 nm), which requires use of a highly sensitive resist composition. be able to.
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 method for measuring the average molecular weight of the polymer, the method for evaluating the solubility of the polymer, and the method for evaluating the sensitivity of the resist composition are as follows.

[Weight average molecular weight measurement]
The weight average molecular weight (Mw) of the polymer was 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: 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: About 20 mg of standard polystyrene was dissolved in 5 mL of THF and injected into a separation column under the above conditions using a solution filtered through a 0.5 μm membrane filter, 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).

[Evaluation of solubility of polymer]
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 was measured. Complete dissolution was judged visually.

[Sensitivity evaluation of resist composition]
<Preparation of resist composition>
A resist composition was prepared so as to have the following composition.
Polymer: 100 parts by mass (in terms of solid content),
Photoacid generator: 2 parts by mass of triphenylsulfonium triflate,
Solvent: PGMEA (amount that gives a polymer concentration of 12.5% by mass).

<Sensitivity measurement>
The resist composition prepared above 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 thin film having a thickness of 300 nm. Using an ArF excimer laser exposure apparatus (manufactured by RISOTEC Japan, VUVES-4500 (product name)), 18 shots having an area of 10 mm × 10 mm were exposed by changing the exposure amount. Next, after post-baking (PEB) at 110 ° C. for 60 seconds, 2.38 mass% tetramethylammonium hydroxide at 23 ° C. using a resist development analyzer (manufactured by RISOTEC Japan, RDA-800 (product name)). The resist film was developed with an aqueous solution for 65 seconds, and the change in the resist film thickness during development was measured for each exposure amount of the resist film.

<Analysis>
Based on the data of change over time of the obtained resist film thickness, the logarithm of the exposure amount (unit: mJ / cm ² ) and the ratio of the remaining film thickness at the time of development for 60 seconds with respect to the initial film thickness (unit: %, Hereinafter referred to as the remaining 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.

[Examples 1-8 and Comparative Examples 1-8]
[Production of polymer]
Polymers were produced under the blending and dropping conditions shown in Tables 1 and 2. The unit of the blending amounts shown in Tables 1 and 2 is “part by mass”.
The monomers in the first mixture and the charging ratio (mol%) are as follows. Dimethyl-2,2′-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, V601 (trade name)) was used as a polymerization initiator.

(Examples 1-3 and Comparative Examples 1-3)

(Example 4 and Comparative Example 4)

(Example 5 and Comparative Example 5)

(Example 6 and Comparative Example 6)

(Example 7 and Comparative Example 7)

(Example 8 and Comparative Example 8)

First, a flask equipped with a nitrogen inlet, a stirrer, a condenser, two dropping funnels, and a thermometer was used as a reactor. In advance, a solvent was charged in a flask (reactor) under a nitrogen atmosphere.
Next, 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 1st mixture was dripped in the flask over 4 hours from one dropping funnel (it describes as "funnel 1" in a table | surface) while maintaining the temperature in a flask at 80 degreeC. The dropping speed was constant.
In Examples 1-8, the 2nd mixture was dripped in the flask from the other dropping funnel (it describes as "funnel 2" in a table | surface) simultaneously with the dripping start of the 1st mixture. The dropping speed was constant. The dropping time from the funnel 2 was as shown in the table. Examples 1 to 6 were 0.1 hour, Example 7 was 0.3 hour, and Example 8 was 0.2 hour.
In Comparative Example 3, dropping of the second mixture was first started from the funnel 2, and dropping from the funnel 1 was started after 30 minutes.
In Comparative Examples 1 and 4-8, the second mixture and funnel 2 were not used.
In any example, after the dropping of the first mixture (funnel 1) was completed, the temperature in the flask was maintained at 80 ° C. for 3 hours to obtain a reaction solution containing the target polymer.
When 12.5% (30 minutes) of the total monomer supply period (4 hours) from the funnel 1 has elapsed, the total supply of each of the monomer and polymerization initiator already supplied in the flask Tables 1 and 2 show the ratio (unit: mass%) to the amount.

[Purification of polymer]
Next, the obtained reaction solution was added dropwise to a mixed solvent of about 10 times the amount of methanol and water (methanol / water = 80/20 volume ratio) with stirring to obtain a white precipitate (polymer). It was. The precipitate was separated by filtration and again poured into a mixed solvent of methanol and water in the same amount as above (methanol / water = 90/10 volume ratio), and the precipitate was washed with stirring. And the precipitate after washing | cleaning was separated by filtration, and 10 g of polymer wet powder was dried at 40 degreeC under pressure reduction for about 40 hours. Table 3 shows the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the obtained polymer. Further, the solubility of the obtained polymer was evaluated by the above method. The results are shown in Table 3.

[Production of resist composition]
The remainder of the polymer wet powder was charged into 920 g of PGMEA and completely dissolved, and then passed through a nylon filter having a pore diameter of 0.04 μm (P-NYLON N66FILTER 0.04M (trade name) manufactured by Nippon Pole Co., Ltd.). And filtered.
The polymer solution was heated under reduced pressure to distill off methanol and water, and further PGMEA was distilled off to obtain a polymer 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 polymer solution thus obtained, 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 evaluation results are shown in Table 3.
Table 3 also shows the ratio (mass%) of the polymerization initiator supplied into the reactor during 30 minutes (period of initial monomer supply of 12.5%) from the start of dropping of the funnel 1.

(Evaluation results)
Polymer obtained by supplying 25% or more of the total amount of polymerization initiator used in the reactor during the initial period of 12.5% of the total monomer supply period supplied into the reactor (Examples 1-8) were excellent in the solubility to a resist solvent, and the highly sensitive resist composition was obtained.
On the other hand, even if a polymer was produced using monomers having the same composition as in Examples 1 to 8, the initial 12.5% of the total supply period of monomers supplied into the reactor. The polymer (Comparative Examples 1 to 8), in which less than 25% of the total amount of the polymerization initiator used in the period of (5) was supplied into the reactor, took time to completely dissolve in the resist solvent. The solubility in the solvent was low. Moreover, the sensitivity of the resist composition containing the polymer of Comparative Examples 1-8 was lower than the Example.
For example, when Examples 2 and 3 and Comparative Examples 1 to 3 are compared, the monomer compositions are the same, and Mw of the obtained polymers is almost the same, but Examples 2 and 3 are comparative. Compared with Examples 1-3, solubility and sensitivity are remarkably excellent.

Claims (6)

A method for producing a polymer for lithography used for producing a resist composition,
While supplying the monomer and a polymerization initiator into the reactor, we have a step of generating a polymer in the reactor,
The monomer is a monomer having an ethylenic double bond, and the polymerization initiator is a radical polymerization initiator,
When 12.5% by mass of the total monomer supply is supplied into the reactor,
A method for producing a polymer for lithography , wherein 25% by mass or more of the total supply amount of the polymerization initiator is supplied into the reactor (however, a part of the polymerization initiator is contained in the reactor) Is charged in advance and heated to the polymerization temperature, and then the polymerization initiator and monomer are supplied). When the supply rate of the monomer into the reactor is constant and 12.5% of the total supply period during which the monomer is supplied into the reactor has elapsed,
2. The method for producing a lithographic polymer according to claim 1, wherein 25% by mass or more of the total supply amount of the polymerization initiator is supplied into the reactor. The method for producing a lithographic polymer according to claim 1 or 2, wherein a supply rate of the polymerization initiator into the reactor changes with time. The method for producing a polymer for lithography according to any one of claims 1 to 3, wherein the supply of the monomer into the reactor and the supply of the polymerization initiator are simultaneously started. A step of producing a lithographic polymer for the manufacturing method according to any one of claims 1 to 4,
The manufacturing method of a resist composition including the process of melt | dissolving the obtained polymer for lithography, and the compound which generate | occur | produces an acid by irradiation of actinic light or a radiation in a resist solvent. A step of producing a resist composition by the method of producing a resist composition according to claim 5;
A step of applying the obtained resist composition onto a work surface of a substrate to form a resist film, a step of exposing the resist film, and developing the exposed resist film using a developer The manufacturing method of the board | substrate with which the pattern was formed including the process to perform.