JP5384421B2 - Method for producing copolymer for semiconductor lithography - Google Patents

Description

  The present invention relates to a method for producing a lithographic copolymer used in the production of a semiconductor, and more specifically, formation of a fine pattern such as a resist film using various radiations such as deep ultraviolet rays, X-rays and electron beams. The present invention relates to a method for producing a copolymer for semiconductor lithography used in the above.

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, miniaturization has rapidly progressed due to advances in lithography technology. As a technique for miniaturization, the exposure light source is generally shortened in wavelength. Specifically, conventionally, ultraviolet rays typified by i-line have been used, but nowadays, krypton fluoride (KrF) is used. An excimer laser (wavelength 248 nm) has become the center of mass production, and an argon fluoride (ArF) excimer laser (wavelength 193 nm) has begun to be introduced in the mass production process. Research is also being conducted on lithography techniques using a fluorine dimer (F ₂ ) excimer laser (157 nm), extreme ultraviolet (EUV), electron beam (EB), or the like as a light source (radiation source).

  In these lithography techniques, a chemically amplified positive lithography copolymer is suitably used. In this copolymer, a polar group soluble in an alkali developer (hereinafter sometimes referred to as “alkali-soluble group”) is substituted with an acid that is unstable and suppresses solubility in an alkali developer. A repeating unit having a structure protected by a group (hereinafter sometimes referred to as “acid-dissociable dissolution inhibiting group”) (hereinafter also referred to as “acid-dissociable structure”) and adhesion to a semiconductor substrate or the like It is configured to include a repeating unit having a polar group for enhancing or adjusting the solubility in a lithography solvent or an alkali developer.

  For example, in lithography using a KrF excimer laser as an exposure source, a repeating unit obtained by protecting a repeating unit derived from hydroxystyrene and a phenolic hydroxyl group derived from hydroxystyrene with an acid dissociable, dissolution inhibiting group such as an acetal structure or a quaternary hydrocarbon group. A copolymer having a unit or a repeating unit in which a carboxyl group derived from (α-alkyl) acrylic acid is protected with an acid dissociable, dissolution inhibiting group such as an acetal structure or a quaternary hydrocarbon group (Patent Documents 1 to 4, etc.) For example). In addition, in order to improve dry etching resistance and the difference in dissolution rate with respect to an alkaline developer before and after exposure, a copolymer having a repeating unit having an alicyclic hydrocarbon group as an acid dissociable, dissolution inhibiting group (Patent Documents 5 to 5) 6) is also known.

  In lithography using a shorter wavelength ArF excimer laser or the like as an exposure source, a copolymer having no repeating unit derived from hydroxystyrene having a high extinction coefficient with respect to a wavelength of 193 nm has been studied, and adhesion to a semiconductor substrate or the like has been investigated. A copolymer having a lactone structure as a repeating unit (see, for example, Patent Documents 7 to 10) is known as a polar group for increasing or adjusting the solubility in a lithography solvent or an alkali developer.

  On the other hand, in recent years, a technique called immersion lithography has been proposed. This is a technique in which exposure is performed by immersing a liquid such as water having a refractive index higher than that of air between the objective lens and the lithography thin film. Conventional lithography in which an air layer exists between the objective lens and the thin film (hereinafter referred to as “lithography thin film”). Compared to the case of “dry lithography”), the numerical aperture of the lens can be increased even if the wavelength of the light source is the same, and the depth of focus can be increased even if the numerical aperture is the same. A finer pattern can be formed even with a light source. For this reason, immersion lithography centering on ArF excimer laser light sources has been actively studied as a next-generation lithography, and as a copolymer used for ArF immersion lithography, a conventional ArF dry crystal is used. The same copolymer as that known in lithography has been proposed (see Patent Documents 11 to 13, etc.).

  In such a chemically amplified positive lithography copolymer, the acid value of the monomer as a polymerization raw material and the copolymer obtained by polymerizing the monomer is 200 mg-KOH / g (about 3.6 mmol). / G) It is known that when the amount is less than or equal to, there is no change with time during storage, and a predetermined pattern can be formed with high accuracy (see Patent Document 14). However, in this patent document, only an example in which the amount is reduced to 10 mg-KOH / g (about 0.2 mmol / g) is disclosed, and the acid value of the copolymer is further reduced to a level lower by one digit or more. It has not been known at all that a composition for semiconductor lithography excellent in contrast of the developing speed with respect to the exposure amount (hereinafter sometimes referred to as developing contrast, which is an index representing the sharpness of the resolution pattern) can be obtained. It was.

JP 59-045439 A Japanese Patent Laid-Open No. 05-113667 JP-A-10-026828 JP 62-115440 A JP 09-073173 A JP-A-10-161313 Japanese Patent Laid-Open No. 09-090637 JP-A-10-207069 Japanese Patent Laid-Open No. 2000-026446 JP 2001-242627 A JP 2005-227332 A JP 2005-234015 A JP 2005-316259 A Japanese Patent Laid-Open No. 2001-166481

  The present invention has been made in view of the above-described background art, and an object of the present invention is to provide a method for producing a chemically amplified positive-type copolymer for semiconductor lithography, which has a high development contrast and excellent resolution performance for fine patterns. It is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have at least a repeating unit (A) having a structure in which an alkali-soluble group is protected with an acid dissociable, dissolution inhibiting group, and a repeating unit (B) having a lactone structure. And a copolymer containing a repeating unit (C) having an alcoholic hydroxyl group is analyzed by a method for accurately quantifying the acid value of the copolymer, and the acid value of the copolymer is at a lower level than before. As a result of the control, it was found that the above-mentioned problems can be solved, and the present invention has been completed.

  That is, the problem of the prior art can be solved by the following configuration.

[1] At least a repeating unit (A) having a structure in which an alkali-soluble group is protected with an acid dissociable, dissolution inhibiting group, a repeating unit (B) having a lactone structure, and a repeating unit (C) having an alcoholic hydroxyl group A method for producing a copolymer comprising at least one selected from a monomer that provides a repeating unit (A), a monomer that provides a repeating unit (B), and a monomer that provides a repeating unit (C). After the step of contacting at least one type with an ion exchange resin in a state dissolved in an organic solvent, the resulting copolymer is dissolved in a solvent by subjecting it to copolymerization, and then using bromothymol blue as an indicator, the acid value was determined by the method of neutralization titration with alkali metal oxide-containing solution, the following 0.01 mmol / g, and, the monomer in a state dissolved in ethyl acetate, the additive Contacting both by stirring after switching on the Manai 20-25 ° C. water, separated to process the co semiconductor lithography, characterized in that a value lower than when subjected to copolymerization after undergoing one A method for producing a polymer.

[ 2 ] The acid dissociable, dissolution inhibiting group of the repeating unit (A) is represented by the formula (L1)

{In Formula (L1), o is a binding site as an acid dissociable, dissolution inhibiting group, R ₁₃ and R ₁₄ are each independently a hydrocarbon group having 1 to 4 carbon atoms, and R ₁₅ is a carbon number 1 to 12 R ₁₅ may be bonded to R ₁₃ or R ₁₄ to form a ring. }
Or formula (L2)

{In Formula (L2), o is a bonding site as an acid dissociable, dissolution inhibiting group, R ₁₆ and R ₁₇ are each independently a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and R ₁₈ is a carbon number. Represents a hydrocarbon group of 1 to 12, and R ₁₆ may combine with R ₁₇ or R ₁₈ to form a ring. }
The manufacturing method of the copolymer for semiconductor lithography as described in [1] selected from the structure represented by these.

[ 3 ] The repeating unit (A) is represented by the formula (A)

{In Formula (A), R ₁₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms that may be substituted by a fluorine atom, and R ₁₁ represents 6 to 6 carbon atoms that may include an oxygen atom or a sulfur atom. 12 represents an alicyclic hydrocarbon group, n represents an integer of 0 or 1, and R ₁₂ represents an acid dissociable, dissolution inhibiting group represented by the formula (L1) or (L2). }
[1] The method for producing a copolymer for semiconductor lithography according to [1] .

[ 4 ] The repeating unit (B) has the formula (B)

[In the formula (B), R ₂₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and R ₂₁ may contain a single bond, an oxygen atom or a sulfur atom. A good alicyclic hydrocarbon group having 5 to 12 carbon atoms, L ₃ is represented by the formula (L3)

{In Formula (L3), R _{22 to} R ₂₉ are single bonds in which one or two of them are bonded to R ₂₁ , and the rest represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group. , M represents an integer of 0 or 1. }, L ₃ is bonded to R ₂₁ with 1 or 2 single bonds. ]
[1] The method for producing a copolymer for semiconductor lithography according to [1] .

[ 5 ] The repeating unit (C) is represented by the formula (C)

{In Formula (C), R ₃₃ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and R _{34 to} R ₃₆ each independently represents a hydrogen atom or a hydroxyl group. , At least one of R _{34 to} R ₃₆ is a hydroxyl group. }
[1] The method for producing a copolymer for semiconductor lithography according to [1] .

  According to the present invention, it is possible to provide a method for producing a chemically amplified positive-type copolymer for semiconductor lithography, which has a high development contrast and an excellent resolution performance of a fine pattern, thereby enabling the production of a highly integrated semiconductor device. Become.

  Hereinafter, the present invention will be described in more detail.

1. Copolymer Structure The copolymer for semiconductor lithography produced according to the present invention includes at least a repeating unit (A), a repeating unit (B), and a repeating unit (C).

(1) Repeating unit (A)
The repeating unit (A) is a repeating unit having a structure in which an alkali-soluble group is protected with an acid dissociable, dissolution inhibiting group, and functions to change the solubility of the copolymer in an alkali developer. The alkali-soluble group is preferably a polar group having a pKa of 12 or less at 25 ° C. in water, and particularly preferably a polar group having a pKa of 10 or less at 25 ° C. in water. Examples thereof include a phenolic hydroxyl group, a fluoroalcoholic hydroxyl group, a carboxyl group, a sulfo group, and the like, and a carboxyl group is particularly preferred from the viewpoint of light transmittance at 193 nm, storage stability, and the like. The acid dissociable, dissolution inhibiting group substitutes for hydrogen of such an alkali-soluble group and binds to an oxygen atom to suppress solubility in an alkali developer.

The acid dissociable, dissolution inhibiting group preferably has a structure selected from formula (L1) or formula (L2).

In the formula (L1), o represents a binding site as an acid dissociable, dissolution inhibiting group. R ₁₃ and R ₁₄ each independently represent a hydrocarbon group having 1 to 4 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i- A butyl group etc. can be mentioned. R ₁₅ represents a hydrocarbon group having 1 to 12 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, cyclopentyl group, cyclohexyl it can be exemplified group, a norbornyl group, a tricyclo [5.2.1.0 ^{2, 6]} decanyl group, an adamantyl group, a tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl group . R ₁₅ is bonded to R ₁₃ or R ₁₄ to form a ring, specifically a cyclopentane ring, a cyclohexane ring, a norbornane ring, a tricyclo [5.2.1.0 ^2,6 ] decane ring, an adamantane ring, a tetracyclo ring. [4.4.0.1 ^2,5 .1 ^7,10] may form a dodecane ring.

In particular, R ₁₅ or R ₁₅ is bonded to R ₁₃ or R ₁₄ to form a ring, specifically a cyclopentane ring, a cyclohexane ring, a norbornane ring, or tricyclo [5.2.1.0 ^2,6 ]. decane ring, adamantane ring and include tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecane ring and a large difference in solubility in an alkali developing solution before and after lithography, a fine pattern Preferred for drawing.

In formula (L2), o represents a binding site as an acid dissociable, dissolution inhibiting group. R ₁₆ and R ₁₇ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, specifically, hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n -A butyl group, i-butyl group, etc. can be mentioned. R ₁₈ represents a hydrocarbon group having 1 to 12 carbon atoms, specifically a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, 2-ethylhexyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, a tricyclo [5.2.1.0 ^{2, 6]} decanyl group, an adamantyl group, a tetracyclo [4.4.0.1 ^2,5 .1 ^7,10 ] A dodecanyl group etc. can be mentioned. R ₁₆ may be bonded to R ₁₇ or R ₁₈ to form a ring. Specific examples of the ring in which R ₁₆ is bonded to R ₁₇ include a cyclopentane ring, cyclohexane ring, norbornane ring, tricyclo [5 .2.1.0 ^2,6] decane ring, adamantane ring, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecane ring, etc. _{Further, R 16} is bonded to _{R 18} rings Specific examples of these include a hydrofuran ring and a hydropyran ring.

The repeating unit (A) preferably has a structure represented by the formula (A).

In the formula (A), R ₁₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Specifically, a hydrogen atom, a methyl group, an ethyl group, n- A propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a trifluoromethyl group and the like can be mentioned, and a hydrogen atom, a methyl group and a trifluoromethyl group are preferable.

R ₁₁ is, contain an oxygen atom or a sulfur atom represents an alicyclic hydrocarbon group having 6 to 12 carbon atoms, specifically, norbornane ring, tetracyclo [4.4.0.1 ^{2, 5} .1 ^7,10 ] An alicyclic hydrocarbon group having a dodecane ring, a 7-oxa-norbornane ring, a 7-thia-norbornane ring or the like can be mentioned, and a norbornane ring, tetracyclo [4.4.0.1 ² is preferable. ^{, 5.1 7,10} ] dodecane ring. Note that n is an integer of 0 or 1.

  Specific examples of the repeating unit (A) are shown below, but the present invention is not limited to these specific examples. In addition, the monomer which gives these repeating units can be used individually or in combination of 2 or more types.

(2) Repeating unit (B)
The repeating unit (B) is a repeating unit having a lactone structure and functions to enhance adhesion to a semiconductor substrate or to control solubility in a lithography solvent or an alkali developer. The repeating unit (B) preferably has a structure represented by the formula (B).

In the formula (B), R ₂₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom. Specifically, a hydrogen atom, a methyl group, an ethyl group, n- A propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a trifluoromethyl group and the like can be mentioned, and a hydrogen atom, a methyl group and a trifluoromethyl group are preferable. R ₂₁ represents a single bond or an alicyclic hydrocarbon group having 5 to 12 carbon atoms which may contain an oxygen atom or a sulfur atom, specifically a single bond, a cyclohexane ring, a norbornane ring, tetracyclo [4 .4.0.1 ^2,5 .1 ^7,10] dodecane ring, 7-oxa norbornane ring, 7-thia norbornane ring, can be exemplified an alicyclic hydrocarbon group having, preferably a single bond , Norbornane ring, 7-oxa-norbornane ring.

In the formula (B), L ₃ represents a lactone structure represented by the formula (L3), and is bonded to R ₂₁ with a single bond of 1 or 2.

In the formula (L3), R _{22 to} R ₂₉ are single bonds in which any one or two of them are bonded to R ₂₁ in the formula (B), and the rest are hydrogen atoms or the same C 1-4 as described above. It is a hydrocarbon group or an alkoxy group. M represents an integer of 0 or 1.

  Specific examples of the repeating unit (B) are shown below, but the present invention is not limited to these specific examples. In addition, the monomer which gives these repeating units can be used individually or in combination of 2 or more types.

(3) Repeating unit (C)
The repeating unit (C) is a repeating unit having an alcoholic hydroxyl group, and functions to increase adhesion to a semiconductor substrate or to control solubility in a lithography solvent or an alkali developer. The structure of the repeating unit (C) is particularly preferably a structure represented by the formula (C) because of excellent light transmittance and etching resistance.

In the formula (C), R ₃₃ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, specifically, a hydrogen atom, a methyl group, an ethyl group, n- A propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a trifluoromethyl group and the like can be mentioned, and a hydrogen atom, a methyl group and a trifluoromethyl group are preferable. R _{34 to} R ₃₆ each independently represents a hydrogen atom or a hydroxyl group, and at least one of R _{34 to} R ₃₆ is a hydroxyl group.

  Specific examples of the repeating unit (C) are shown below, but the present invention is not limited to these specific examples. In addition, the monomer which gives these repeating units can be individual or can combine 2 or more types.

(4) Other repeating units In addition to the above repeating units, the copolymer for semiconductor lithography produced according to the present invention is an acid for the purpose of controlling the solubility in an alkali developer or a lithography solvent, if necessary. A repeating unit (D) having a stable dissolution inhibiting group can also be included.

Examples of the repeating unit (D) include a structure represented by the formula (D).

In the formula (D), R ₄₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, specifically, a hydrogen atom, a methyl group, an ethyl group, n- A propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a trifluoromethyl group and the like can be mentioned, and a hydrogen atom, a methyl group and a trifluoromethyl group are preferable. R ₄₁ represents an alicyclic hydrocarbon group having 1 to 12 carbon atoms in which the ester-bonded carbon is a primary to tertiary carbon, or a 1-adamantyl group, specifically, a methyl group, an ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, cyclopentyl group, cyclohexyl group, 2-norbornyl group, 2-isobornyl group, 8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, a 1-adamantyl group, 2-adamantyl group, and a 4-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl group.

  Specific examples of the repeating unit (D) are shown below, but the present invention is not limited to these specific examples. In addition, the monomer which gives these repeating units can be used individually or in combination of 2 or more types.

(5) Repeating unit composition The composition of each repeating unit can be selected as long as the basic performance in semiconductor lithography is not impaired. For example, the repeating unit (A) is usually selected in the range of 10 to 80 mol%, preferably 15 to 70 mol%, more preferably 20 to 60 mol%. The repeating unit (B) is usually selected in the range of 10 to 80 mol%, preferably 15 to 70 mol%, more preferably 20 to 60 mol%. The repeating unit (C) is usually selected in the range of 1 to 50 mol%, preferably 5 to 40 mol%, more preferably 10 to 30 mol%. A repeating unit (D) selects 0-30 mol% normally, Preferably it is 0-20 mol%, More preferably, the range of 0-10 mol% is selected.

(6) Terminal structure The copolymer for semiconductor lithography produced by the present invention already contains a known terminal structure. Usually, a radical structure generated from a radical polymerization initiator is included as a polymerization initiation terminal, and when a chain transfer agent is used, a radical structure generated from a chain transfer agent is included as a polymerization initiation terminal. In the case of chain transfer to a solvent or monomer, a radical structure generated from the solvent or monomer is included as a polymerization initiation terminal. When the termination reaction is recombination termination, both ends can contain polymerization initiation ends, and when disproportionation termination, the polymerization initiation end can be included on one side and the monomer-derived terminal structure can be included on the other side. it can. When a polymerization terminator is used, a polymerization initiation terminal can be included at one end and a terminal structure derived from the polymerization terminator can be included at the other end. A plurality of these initiation reactions and termination reactions may occur in one polymerization reaction, and in that case, a mixture of copolymers having a plurality of terminal structures is formed. The polymerization initiator, chain transfer agent, and solvent that can be used in the present invention will be described later.

(7) If the molecular weight and the weight average molecular weight (Mw) of the copolymer are too high, the solubility in a resist solvent or an alkali developer will be low, while if too low, the coating performance of the resist will be poor. Is preferably in the range of 1,000 to 40,000, more preferably in the range of 1,500 to 30,000, and particularly preferably in the range of 2,000 to 20,000. preferable. The molecular weight distribution (Mw / Mn) is preferably in the range of 1.0 to 5.0, more preferably in the range of 1.0 to 3.0, and 1.2 to 2.5. It is particularly preferable that the value falls within the range.

  The copolymer for semiconductor lithography produced by the present invention is characterized in that the acid value determined by a predetermined method is 0.01 mmol / g or less.

2. Method for Quantifying Acid Value The acid value of the copolymer produced according to the present invention is determined by dissolving the copolymer to be measured in a solvent and performing neutralization titration with an alkali metal hydroxide-containing solution using bromothymol blue as an indicator. Ask for. This method is preferable for quantifying the acid value of a copolymer having a lactone structure, for the following reason.

  That is, the lactone structure is easily hydrolyzed at a pH of 8 or more. In addition, when a weak acid such as a carboxyl group is neutralized with a strong base such as an alkali metal hydroxide, the change in pH with respect to the titration is gradual when the pH is less than 7, and is maximum between 7 and 10 in pH. It becomes. For this reason, it is necessary to use an indicator that changes color when the pH is 7 or more and less than 8, and the optimal indicator is bromothymol blue. The indicator changes from neutral green to basic blue at pH = 7.6.

Examples of methods other than the above include potentiometric titration, ¹³ C-NMR, and ¹ H-NMR methods. However, in the method by potentiometric titration, it is difficult to determine the end point, and the lactone is hydrolyzed by an excessively dropped base, so that the determination is substantially difficult. Further, in the method by ¹³ C-NMR, since the S / N ratio is low, it is difficult to determine the minute peak. When the carboxyl group is determined, the main chain of the (meth) acrylic acid ester copolymer The quantification is substantially difficult because the carbonyl and the carbonyl of the lactone structure often do not separate from the peak. Furthermore, in the method by ¹ H-NMR, since the peak of acidic hydrogen is broad, it is difficult to integrate minute peak areas, and it is substantially difficult to quantify.

  Hereinafter, a method for performing neutralization titration with an alkali metal hydroxide-containing solution using bromothymol blue as an indicator will be described.

  The alkali metal hydroxide used for titration is preferably sodium hydroxide or potassium hydroxide used for normal neutralization titration. The alkali metal hydroxide is dissolved in water or a mixed solution of water and an organic solvent, and preferably has a concentration in the range of 0.0001 to 1 mol / L, particularly preferably in the range of 0.001 to 0.1 mol / L. And It is preferable to obtain an accurate concentration of the prepared titrant by a method such as titration using a standard solution before use. Moreover, it is preferable to use the water used for the titrant in which impurities such as carbon dioxide have been reduced in advance by a method such as filter filtration, ion exchange treatment, distillation, or deaeration.

  The solvent that dissolves the copolymer during titration is a solvent that dissolves the copolymer and the indicator, and a solvent that does not precipitate the copolymer even when the titrant is dropped is selected. When the copolymer is water-soluble, water, a water-soluble organic solvent and a mixture thereof can be selected, and water is particularly preferable. When the copolymer is water-insoluble, an organic solvent that dissolves the copolymer and preferably dissolves water preferably 1% or more, particularly preferably 10% or more, is used alone or in combination of two or more. Can be used.

  Specific examples of the organic solvent include acetone, methyl ethyl ketone, methyl isoamyl ketone, methyl amyl ketone, cyclohexanone and other ketones; methanol, ethanol, isopropanol and other alcohols; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Ether alcohols such as butyl ether, propylene glycol monomethyl ether and 3-methoxy-3-methyl-1-butanol; ether esters which are ester compounds of the ether alcohols and acetic acid; methyl acetate, ethyl acetate, butyl acetate, Esters such as methyl propionate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, γ-butyrolactone; Ethers such as hydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; aromatic hydrocarbons such as toluene and xylene; amides such as N, N-dimethylformamide and N-methylpyrrolidone; dimethyl sulfoxide and acetonitrile Etc.

3. Method for producing a copolymer following, a method for manufacturing the copolymer for semiconductor lithography of the present invention. The production method of the present invention can comprise at least a step (Q) for removing an acid from a monomer and a step (P) for radical polymerization of the monomer in a heated organic solvent. The step (R) of removing unreacted substances such as monomers, polymerization initiators, and other low molecular weight components such as oligomers from the copolymer (R), removing low boiling point impurities, A step (S) of substituting a solvent suitable for lithography, a step (T) of reducing metal impurities that are undesirable for the formation of semiconductors, and a step (U) of reducing substances that cause pattern defects such as microgels. It can also be combined.

(1) Process (Q)
Step (Q) is a step of removing acidic substances such as acid raw materials, acid catalysts, and by-produced acids used in the synthesis process from the monomer. When the acidic substance remains, in the step (P), a part of the acid dissociable, dissolution inhibiting group of the monomer giving the repeating unit (A) is eliminated, or when the acidic substance is a polymerizable substance, the acidic substance is shared. Polymerization may result in the formation of acidic functional groups such as carboxyl groups in the copolymer. In order to set the acid value of the copolymer to 0.01 mmol / g, the acidic substance contained in the monomer is removed, and the acid value of the monomer is preferably 0.01 mg / g or less, particularly preferably 0. It is preferable to reduce to 0.005 mg / g or less.

  As a method of removing the acidic substance, (Q1) the monomer is dissolved in an organic solvent that separates into two phases with water, mixed with water to extract the acidic component into the aqueous phase, and the aqueous phase is separated and removed. Examples thereof include (Q2) a method in which a monomer dissolved in an organic solvent is brought into contact with an ion exchange resin and an acidic component is adsorbed on the ion exchange resin or ion exchanged to be removed.

  As the organic solvent used in (Q1), a solvent that dissolves the monomer and separates it from water is selected from the solvents described above, but it may be used alone or in combination of two or more. When the concentration of the monomer is too high, the extraction efficiency of the acidic component is lowered, and when it is too low, the production efficiency is lowered. Select the mass% range. If the amount of water as the extraction solvent is too small, extraction of acidic components becomes insufficient, and if it is too large, production efficiency is lowered, which is not preferable, and usually 0.1 to 10 times by mass of the monomer solution, preferably Is selected in the range of 0.2-5 mass times, particularly preferably 0.3-3 mass. If the temperature at the time of extraction is too high, it is not preferable because the liquid separation property is reduced or the monomer or solvent is altered, and if it is too low, water is solidified. Usually, the range of 0-60 ° C, preferably 5-50 ° C, particularly preferably 10-40 ° C is selected.

  As the organic solvent used in (Q2), a solvent that dissolves the monomer is selected from the solvents described above. As the ion exchange resin, resins having anion adsorption ability and anion exchange ability, which are usually called anion exchange resins, can be used alone or in combination. In addition, an anion exchange resin may be used in combination with a resin having a cation exchange ability, usually called a cation exchange resin. In addition, since a base component may elute from an anion exchange resin, it is particularly preferable to use it in combination with a cation exchange resin.

Examples of anion exchange resins include polystyrene having a substituent having anion adsorption ability or anion exchange ability, (meth) acrylate-divinylbenzene copolymer, styrene-divinylbenzene copolymer, and an alkylene group. Examples thereof include resins such as polystyrene, (meth) acrylic acid ester-divinylbenzene copolymer, and styrene-divinylbenzene copolymer. Examples of the substituent having an anion-adsorbing ability include a substituent having a primary to tertiary amino group, specifically, an N, N-dimethylaminomethyl group, an N-methylaminomethyl group, an amino group. A methyl group, a N, N-diethylaminomethyl group, etc. can be mentioned, Especially preferably, it is a N, N-dimethylaminomethyl group. Examples of the substituent having an anion adsorption ability include a substituent having a quaternary ammonium ion, and the counter cation is preferably a hydroxide anion. Specifically, the following (E1) to (E4) are shown. Particularly preferred is (E1) or (E2).

  Examples of the cation exchange resin include resins having a functional group having a cation exchange ability such as carboxylic acid and sulfonic acid in place of the functional group having anion adsorption ability or anion exchange ability in the anion exchange resin described above. Particularly preferred is a resin substituted with a sulfonic acid group.

  In order to bring the solution in which the monomer is dissolved into contact with the ion exchange resin, the ion exchange resin may be charged into the monomer solution and stirred, or the monomer solution may be added to the ion exchange layer filled with the ion exchange resin. It may be passed through. If the amount of the ion exchange resin used is too small, the acidic substances cannot be removed, and if too large, the production efficiency is lowered, which is not preferable. The range in which the ion exchange capacity is usually 1.2 to 100 equivalent times, preferably 1.5 to 50 equivalent times, particularly preferably 1.5 to 20 equivalent times with respect to the acidic substance is selected.

When the monomer solution is passed through the ion exchange layer, LHSV (Liquid Hourly
It is an abbreviation for Space Velocity and represents the space velocity of fluid. Here, it is represented by a value obtained by dividing the flow rate of the monomer solution by the volume of the ion exchange layer. ) Is too fast, the removal efficiency of the acidic substance is lowered, and if it is too slow, the production efficiency is lowered, which is not preferable. LHSV is usually 0.1 to 100 / hr, preferably 0.5 to 50 / hr, particularly preferably. Selects the range of 1-20 / hr.

  If the layer height of the ion exchange layer is too low, the removal efficiency of the acidic substance is reduced by a short pass, and if it is too high, it is difficult to pass the liquid due to the differential pressure, and it is not preferable, and usually 5 to 500 cm, preferably 10 to 300 cm, Particularly preferably, a range of 20 to 200 cm is selected. If the temperature is too high, it is not preferable because the ion exchange resin, monomer, and solvent change, and if it is too low, it is not preferable because ion exchange or adsorption becomes insufficient, and is usually 0-60 ° C., preferably 5-50. A range of 10 ° C, particularly preferably 10-40 ° C is selected.

  After removing the acidic component in this way, it may be used as it is in the step (P), but preferably after the separation of the organic solvent by a method such as heating under reduced pressure to distill off the organic solvent (step ( P).

(2) Process (P)
Step (P) is a step of radical polymerization of a monomer in an organic solvent in the presence of a radical polymerization initiator, and can be performed by a known method. For example, the (P1) monomer is dissolved in a solvent together with a polymerization initiator and heated to polymerize as it is, and the (P2) monomer is dissolved together with the polymerization initiator in a solvent as needed and heated. (P3) A so-called independent polymerization in which a monomer and a polymerization initiator are separately dissolved in a solvent as required and dropped into a heated solvent for polymerization. Examples thereof include a dropping method, an initiator dropping method in which the monomer (P4) is dissolved in a solvent and heated, and a polymerization initiator separately dissolved in the solvent is dropped and polymerized.

  Here, (P1) batch temperature raising method and (P4) initiator dropping method are in the polymerization system, and (P2) mixed dropping method is in the dropping liquid storage tank before dropping into the polymerization system, unreacted monomer. Since there is an opportunity to come into contact with a low concentration of radicals in a high concentration state, a high molecular weight polymer (high polymer) having a molecular weight of 100,000 or more, which is one of the causes of pattern defects, tends to be generated. Compared to this, the (P3) independent dropping method does not coexist with the polymerization initiator in the dropping liquid storage tank, and maintains a low unreacted monomer concentration even when dropped into the polymerization system. Since it does not generate | occur | produce, (P3) independent dropping method is especially preferable as a polymerization method in this invention. In the (P2) mixed dropping method and the (P3) independent dropping method, the composition of the monomer to be dropped, the composition ratio of the monomer, the polymerization initiator, and the chain transfer agent may be changed with the dropping time.

As the polymerization initiator, those known as radical polymerization initiators can be used. Preferred are radical polymerization initiators such as azo compounds and peroxides. Specific examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl-2,2′-azobisisobutyrate, 1, Examples include 1'-azobis (cyclohexane-1-carbonitrile), 4,4'-azobis (4-cyanovaleric acid), and the like. Specific examples of the peroxide include decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, succinic acid peroxide, tert-butylperoxy-2- Examples thereof include ethyl hexanoate, tert-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate and the like. These can be used alone or in combination. The amount of the polymerization initiator used should be selected according to the production conditions such as the target Mw, the raw material monomer, the polymerization initiator, the chain transfer agent and the type and composition ratio of the solvent, the polymerization temperature and the dropping rate. Can do.

  As the chain transfer agent, a known chain transfer agent can be used as necessary. Of these, thiol compounds are preferred, and a wide range of known thiol compounds can be selected. Specific examples include t-dodecyl mercaptan, mercaptoethanol, mercaptoacetic acid, mercaptopropionic acid, and the like. In addition, a thiol compound having a structure in which a 2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propylidene group is bonded to saturated carbonization has an effect of suppressing the roughness and defects of the lithography pattern. Particularly preferred.

  The amount of the chain transfer agent used should be selected according to the production conditions such as the target Mw, the raw material monomer, the polymerization initiator, the type and composition ratio of the chain transfer agent and the solvent, the polymerization temperature and the dropping rate. Can do. In the (P1) batch temperature raising method, the chain transfer agent can be heated by dissolving in a solvent together with the monomer and the polymerization initiator, (P2) mixed dropping method, (P3) independent dropping method, (P4) In the initiator dropping method, it may be dropped by mixing with a monomer, may be dropped by mixing with a polymerization initiator, or may be used by dissolving in a solvent to be heated in advance. .

  The polymerization solvent is not particularly limited as long as it is a compound that dissolves a monomer, a polymerization initiator, a chain transfer agent, and a copolymer obtained by polymerization. Specific examples of the solvent include the organic solvents exemplified as the solvent that can be used for the determination of the acid value, and they can be used alone or in combination of two or more.

  The polymerization temperature in the step (P) can be appropriately selected according to the boiling point of the solvent, monomer, chain transfer agent, etc., the half-life temperature of the polymerization initiator, and the like. Since polymerization is difficult to proceed at low temperatures, there is a problem in productivity, and when the temperature is higher than necessary, there is a problem in terms of stability of monomers and copolymers. Therefore, it is preferably selected in the range of 40 to 120 ° C, particularly preferably in the range of 60 to 100 ° C.

  The dropping time in the (P2) mixed dropping method and the (P3) independent dropping method is that the molecular weight distribution tends to be wide when it is short, or the temperature of the polymerization solution is lowered because a large amount of solution is dropped at once. Is not preferable. On the other hand, if the time is long, it is not preferable because an excessive heat history is applied to the copolymer and productivity is lowered. Therefore, it is selected from the range of usually 0.5 to 24 hours, preferably 1 to 12 hours, particularly preferably 2 to 8 hours.

  The temperature is maintained for a certain time after completion of the dropping in the (P2) mixed dropping method and (P3) the independent dropping method, and after the temperature rising to the polymerization temperature in the (P1) batch temperature raising method and (P4) initiator dropping method. It is preferable that the remaining unreacted monomer is reacted by aging by further increasing the temperature or by aging. If the aging time is too long, the production efficiency per hour is lowered, and an unnecessarily high heat history is applied to the copolymer. Therefore, it is selected within the range of usually 12 hours or less, preferably 6 hours or less, particularly preferably 1 to 4 hours.

(3) Process (R)
In step (R), unreacted substances such as monomers and polymerization initiators and oligomers and other low molecular weight components contained in the copolymer obtained through step (P) are extracted by solvent and removed. It is a process. As the method, for example, (R1): a method of adding a poor solvent to precipitate a copolymer and then separating the solvent phase, (R1a): (R1) followed by adding a poor solvent, After washing, a method of separating the solvent phase, (R1b): (R1) followed by adding a good solvent, re-dissolving the copolymer, further adding a poor solvent to reprecipitate the copolymer, (R2): a method for separating a poor solvent phase by adding a poor solvent to form a two phase of a poor solvent phase and a good solvent phase, (R2a): a poor solvent following (R2) And the good solvent phase is washed, and then the poor solvent phase is separated. Note that (R1a), (R1b), and (R2a) may be repeated or combined.

  The poor solvent is not particularly limited as long as it is a solvent in which the copolymer is difficult to dissolve. For example, water, alcohols such as methanol and isopropanol, saturated hydrocarbons such as hexane and heptane, and the like can be used. Moreover, a good solvent will not be restrict | limited especially if a copolymer is easy to melt | dissolve, It can use as 1 type, or 2 or more types of mixed solvents. In terms of management of the production process, the same solvent as the polymerization solvent is preferable. Examples of the good solvent include the same solvents as those exemplified as the polymerization solvent in the step (P).

(4) Step (S)
Step (S) is a step of removing low-boiling impurities contained in the copolymer solution or replacing the solvent with a solvent suitable for the next step or the lithography composition. The step of concentrating the polymer solution while heating under reduced pressure, and further concentrating by adding a solvent as necessary (S1), after concentrating the polymer solution as necessary while heating under reduced pressure, While supplying the solvent preferred as the next step or lithography composition, the initial solvent and the supplied solvent are distilled off, and further concentrated as necessary to replace the solvent with a preferred solvent as the next step or lithography composition. It can carry out by the process (S2) to perform.

  This step (S) is performed, for example, when the lithography composition is different from the solvent obtained through the step (P) or the step (R), or when there are undesired impurities in the lithography composition. It is preferable to carry out prior to the step (U) of preparing the lithographic composition.

  Although it is not necessary to go through step (S), it can be once solidified by drying under reduced pressure and then dissolved in another solvent. However, in this operation, impurities and solvent are likely to remain in the solid, On the other hand, it is not preferable because it gives more heat history than necessary.

  The temperature of the step (S) is not particularly limited as long as the copolymer does not deteriorate, but is usually preferably 100 ° C or lower, more preferably 80 ° C or lower, further preferably 70 ° C or lower, particularly preferably 60 ° C or lower. It is. When replacing the solvent, if the amount of the solvent to be supplied later is too small, the low boiling point compound cannot be sufficiently removed, and if it is too large, the replacement takes time, and the copolymer gives more heat history than necessary. It is not preferable. Usually, it can be selected from the range of 1.05 to 10 times, preferably 1.1 to 5 times, particularly preferably 1.2 to 3 times the amount required as a solvent for the finished solution.

(5) Process (T)
Step (T) is a step of reducing a metal component that is not preferable for semiconductor lithography. The metal may be mixed from raw materials, sub-materials, equipment, and other environments, and this amount may exceed the allowable value in semiconductor formation, so it is carried out as necessary. In the step (T), when the polar solvent is a poor solvent in the step (R), the metal content may be reduced. In this case, the step (T) can also be combined with the step (R). Other methods include a step of contacting with a cation exchange resin (T1), a step of contacting with a mixed resin of a cation exchange resin and an anion exchange resin or an acid adsorption resin (T2), a polyamide polyamine epichlorohydrin cation resin, etc. A step (T3) of passing through a filter containing a substance having a positive zeta potential can be selected. These steps can be carried out in combination, and examples of the filter used in step (T3) include CUENO Zeta Plus 40QSH, Zeta Plus 020GN, and Electropore EFII (these are trademarks, and the same applies hereinafter). .)

(6) Process (U)
The step (U) is a step of reducing a microgel such as a high polymer, which is undesirable because it causes pattern defects, by passing a copolymer dissolved in an organic solvent through a filter. The filtration accuracy of the filter is 0.2 μm or less, preferably 0.1 μm or less, particularly preferably 0.05 μm or less. Examples of the material of the filter include polyolefins such as polyethylene and polypropylene, polar group-containing resins such as polyamide, polyester and polyacrylonitrile, and fluorine-containing resins such as fluorinated polyethylene, and polyamide is particularly preferable.

  Examples of the polyamide-based filter include Ultiplez P-Nylon 66 manufactured by Nippon Pole, Ultipor N66, Photo Shield manufactured by Cuno, Electropore IIEF, and the like. Examples of the polyethylene filter include Microguard Plus HC10 and Optimizer D manufactured by Nihon Entegris. These filters may be used alone or in combination of two or more.

(7) Process (V)
The copolymer obtained as described above can be obtained by dissolving a dry solid in one or more lithography solvents, or using a copolymer solution dissolved in a lithography solvent with the same or different lithography solvent as necessary. A dilution-sensitive acid generator (X) {hereinafter referred to as component (X)}, an acid diffusion inhibitor such as a nitrogen-containing organic compound (Y) for preventing acid diffusion to a portion not exposed to radiation. ) {Hereinafter referred to as component (Y)} and, if necessary, other additives (Z) {hereinafter referred to as component (Z)} can be added to finish the chemically amplified resist composition.

  The lithography solvent is not particularly limited as long as it can dissolve each component constituting the lithography composition to form a uniform solution, and any one of conventionally known solvents for chemically amplified resists may be used. It can be used as a mixed solvent of two or more. Usually, the solubility, viscosity, boiling point, absorption of radiation used in lithography, etc. of the composition other than the copolymer are selected from the polymerization solvent in step (P) and the solvent exemplified as the good solvent in step (R). It can be selected in consideration. Particularly preferable resist solvents are methyl amyl ketone, cyclohexanone, ethyl lactate (EL), γ-butyrolactone, and propylene glycol monomethyl ether acetate (PGMEA). Among them, a mixed solvent of PGMEA and other polar solvents is particularly preferable. Further, EL is particularly preferable as the polar solvent to be mixed.

  The amount of the lithographic solvent contained in the lithographic composition is not particularly limited, but is usually a concentration that can be applied to a substrate or the like, and is appropriately set so as to have an appropriate viscosity according to the coating film thickness. Generally, it is used so that the solid content concentration of the lithography composition is in the range of 2 to 20% by mass, preferably 5 to 15% by mass.

  Component (X) can be appropriately selected from those conventionally proposed as a radiation-sensitive acid generator for chemically amplified resists. Examples thereof include onium salts such as iodonium salts and sulfonium salts, oxime sulfonates, diazomethanes such as bisalkyl or bisarylsulfonyldiazomethanes, nitrobenzyl sulfonates, iminosulfonates, disulfones, and the like. Of these, onium salts having a fluorinated alkyl sulfonate ion as an anion are particularly preferable. These may be used alone or in combination of two or more. Component (X) is usually used in the range of 0.5 to 30 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of the copolymer.

  The component (Y) can be appropriately selected from those conventionally proposed as acid diffusion inhibitors for chemically amplified resists. Examples thereof include nitrogen-containing organic compounds, and primary to tertiary alkylamines or hydroxyalkylamines are preferred. Tertiary alkylamines and tertiary hydroxyalkylamines are particularly preferred, with triethanolamine and triisopropanolamine being particularly preferred. These may be used alone or in combination of two or more. The component (Y) is usually used in the range of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of the copolymer.

  Other additives {component (Z)} include organic carboxylic acids, phosphorus oxo acids, and resist film performance for the purpose of preventing deterioration of sensitivity of acid generators, lithography pattern shape, and stability of retention. Compounds commonly used as lithography additives such as additional resins for improving coating properties, surfactants for improving coatability, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, dyes, etc. Can be added as needed. Examples of organic carboxylic acids include malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid, and the like, and these can be used alone or in admixture of two or more. The organic carboxylic acid is used in the range of 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the copolymer.

EXAMPLES Next, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples. In the following examples, abbreviations used have the following meanings.
Monomer Monomer G: .gamma.-butyrolactone-2-yl methacrylate monomer Ma: 2-methyl-2-adamantyl acrylate monomer Oa: 3- hydroxy-1-adamantyl acrylate
Repeat unit G: Repeat unit derived from monomer G Ma: Repeat unit derived from monomer Ma Oa: Repeat unit derived from monomer Oa

Polymerization initiator MAIB: dimethyl-2,2′-azobisisobutyrate
Solvent MEK: Methyl ethyl ketone THF: Tetrahydrofuran PGMEA: Propylene glycol monomethyl ether acetate EL: Ethyl lactate

(1) Measurement of Mw and Mw / Mn of copolymer (GPC)
Measured by GPC. The analysis conditions are as follows.
Equipment: Tosoh GPC8220
Detector: Differential refractive index (RI) detector Column: Showa Denko KF-804L (x3)
Sample: About 0.02 g of the copolymer was dissolved in about 1 ml of tetrahydrofuran. The injection amount into GPC was 60 μl.

(2) Measurement of repeating unit composition and terminal composition of copolymer ( ¹³ C-NMR)
Equipment: AV400 manufactured by Bruker
Sample: About 1 g of copolymer powder and 0.1 g of Cr (acac) ₂ were dissolved in 0.5 g of MEK and 1.5 g of heavy acetone.
Measurement: The sample was placed in a glass tube having an inner diameter of 10 mm and measured under the conditions of a temperature of 40 ° C. and a scan count of 10,000.

(3) Measurement of Eth and γ Values (3-1) Preparation of Lithographic Composition The composition was prepared to have the following composition.
Copolymer: 100 parts by mass Component (X): 4-methylphenyldiphenylsulfonium nonafluorobutanesulfonate 3.5 parts by mass Component (Y): 0.2 parts by mass of triethanolamine Component (Z): Surflon S-381 ( Seimi Chemical) 0.1 parts by weight Solvent: PGMEA 450 parts by weight and EL 300 parts by weight

(3-2) Dry Lithography A lithographic composition was spin-coated on a 4-inch silicon wafer and prebaked (PAB) at 100 ° C. for 90 seconds on a hot plate to form a thin film having a thickness of 350 nm. Using an ArF excimer laser exposure apparatus (VUVES-4500 manufactured by RISOTEC Japan), 18 shots of 10 mm × 10 mm □ were exposed by changing the exposure amount. Next, after post-baking (PEB) at 120 ° C. for 90 seconds, using a resist development analyzer (RDA-800 manufactured by RISOTEC Japan), development is performed with an aqueous 2.38 mass% tetramethylammonium hydroxide solution at 23 ° C. for 180 seconds. The change with time of the resist film thickness during development at each exposure amount was measured.

(3-3) Simulated immersion lithography In the same manner as dry lithography, a lithography composition was spin-coated on a 4-inch silicon wafer and prebaked (PAB) to form a thin film having a thickness of 350 nm. The wafer was dipped in a vat filled with ultrapure water for 30 seconds, then taken out, blown with dry air, and the water droplets were shaken off. Next, using an ArF excimer laser exposure device (VUVES-4500, manufactured by RISOTEC Japan), 18 shots of 10 mm × 10 mm □ were exposed by changing the exposure amount. The exposed wafer was dipped in a vat filled with ultrapure water for 30 seconds, taken out, blown with dry air, and the water droplets were shaken off. Thereafter, in the same manner as dry lithography, post-baking (PEB) is performed, and development is performed using a resist development analyzer (RDA-800 manufactured by RISOTEC Japan), and changes in resist film thickness during development at each exposure amount are measured. did.

(3-4) Analysis Based on the obtained data, the logarithm of the exposure amount (mJ / cm ² ) and the remaining film thickness ratio when developed for 60 seconds with respect to the initial film thickness (hereinafter referred to as the remaining film ratio) ( %) Is plotted (hereinafter referred to as exposure amount-residual film rate curve), Eth (required exposure amount for setting the residual film rate to 0% and represents sensitivity) and γ value (exposure amount). -It is the slope of the tangent line of the remaining film ratio curve and represents the development contrast.
Eth: exposure amount (mJ / cm ² ) at which the exposure amount-residual film rate curve intersects with a residual film rate of 0%
γ value: E ₅₀ (mJ / cm ² ) of exposure amount at 50% of the remaining film rate of the exposure amount-residual film rate curve, and a tangent line at E ₅₀ of the exposure amount-residual film rate curve is a line at which the residual film rate is 100% The exposure amount intersecting with the line having a remaining film rate of 0% was determined as E ₁₀₀ and E ₀ , respectively.
γ = 1 / {log (E ₀ / E ₁₀₀ )}

(4) Measurement of Acid Value 4 g of ethyl acetate solution containing 25% by mass of monomer or 4 g of PGMEA solution containing 25% by mass of copolymer were weighed and dissolved by adding 20 g of tetrahydrofuran. As an indicator, 0.05 g of a methanol solution containing 1% by mass of bromothymol blue was added, and 0.5 g of water was further added to obtain a yellow solution. While stirring this solution, the solution was titrated with a 0.025 mol / L aqueous NaOH solution prepared in advance, and the end point was determined to be a slight blue hue from green. The acid value was calculated as follows.
{Acid value (mmol / g)} = (C _NaOH × V _NaOH ) / (W _szmp × C _poly )
Here, the meaning of each symbol is as follows.
C _NaOH : NaOH concentration (mol / L) in NaOH aqueous solution
V _NaOH : titration volume of NaOH aqueous solution (mL)
W _szmp : Weighing of measurement sample (g)
C _poly : concentration of copolymer contained in sample (mass%)
In addition, titration was implemented 5 times and the average and 3 (sigma) were calculated | required.

Synthesis Example 1-1
Commercially available monomers G {Osaka Organic Chemical Co. Lot 1 (hereinafter, commercially available monomers _{G 1} that.)} Solution obtained by dissolving in ethyl acetate 3.6kg to 1.2 kg, while stirring 20-25 The mixture was poured into 4.8 kg of water kept at 0 ° C., stirred for 15 minutes, and allowed to stand for 30 minutes. After removal of the aqueous phase, while blowing N ₂ gas, by heating under reduced pressure was distilled off light components to obtain a purified monomer G _1. The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 1-2
Instead of commercial monomeric G _1, except for using commercially available monomers G _{2 (Osaka} Organic Chemical Co., lot 2) in the same manner as in Synthesis Example 1-1, to obtain a purified monomer G _2. The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 2-1
Instead of commercial monomeric _{G 1,} commercially available monomers Ma {ENF Ltd. Lot 1 (hereinafter, commercially available monomers Ma ₁ called.)} Except for using in the same manner as in Synthesis Example 1-1, purified Monomer Ma ₁ was obtained. The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 2-2
A purified monomer Ma ₂ was obtained in the same manner as in Synthesis Example 2-1, except that the commercially available monomer Ma ₂ (ENF lot 2) was used instead of the commercially available monomer Ma ₁ . The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 3-1
A solution obtained by dissolving 1.0 kg of commercially available monomer Oa {Idemitsu Kosan Lot 1 (hereinafter referred to as commercially available monomer Oa ₁ )} in 3.0 kg of ethyl acetate is stirred at 20 to 25 ° C. Then, it was poured into 4.0 kg of water kept at 25 ° C., stirred for 15 minutes, and allowed to stand for 30 minutes. After removing the aqueous phase, the mixture was heated under reduced pressure to distill off the light components, and the solution was concentrated. Next, 5.0 kg of hexane was added to precipitate the solid content, and then the solid content was collected by filtration and dried under reduced pressure to obtain purified monomer Oa ₁ . The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 3-2
Purified monomer Oa ₂ was obtained in the same manner as in Synthesis Example 3-1, except that commercially available monomer Oa ₂ (Idemitsu Kosan Lot 2) was used instead of commercially available monomer Oa ₁ . The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Synthesis Example 3-3
1.0 kg of commercially available monomer Oa ₁ was dissolved in 3.0 kg of ethyl acetate. This Oa ₁ solution was charged with 470 g of an ion exchange resin Amberlyst EG-290 made by Organo (a 1: 1 mixture of a substituent-containing anion exchange resin and a sulfonic acid group-containing cation exchange resin in (E1) in the text), Pass 2.4 kg of methanol, then pass 2.4 kg of ethyl acetate, and pass through an ion exchange layer having a diameter of 5 cm and a bed height of 30 cm at LHSV = 5 / hr while maintaining the temperature at 20 to 25 ° C. Liquid. The solution after passing through was heated under reduced pressure to distill off light components and concentrate the solution. Then hexane was added to 5.0 kg, after precipitated solids were collected solids were filtered and dried under reduced pressure to obtain a purified monomer Oa _3. The acid value of the purified monomer was below the lower limit of quantification (0.002 mmol / g).

Example 1
In the container, 3.1 kg of MEK, 0.7 kg of the purified monomer G ₁ obtained in Synthesis Example 1-1 , 1.0 kg of the purified monomer Ma ₁ obtained in Synthesis Example 2-1 , and in Synthesis Example 3-1 . 0.5 kg of the purified monomer Oa ₁ obtained was dissolved to prepare a uniform “monomer solution”. In a separate container, 0.2 kg of MEK and 0.07 kg of MAIB were dissolved to prepare a uniform “initiator solution”. Further, 1.8 kg of MEK was charged into a polymerization tank equipped with a stirrer and a cooler to form a nitrogen atmosphere. After the MEK in the polymerization tank was heated to 79 ° C., the monomer solution and the initiator solution maintained at 25 to 30 ° C. were separately separated at 79 to 81 ° C. over 4 hours at a constant rate using a metering pump. The polymerization was carried out by dropping into a polymerization vessel maintained at a temperature of 2 ° C. After completion of the dropwise addition, the mixture was further aged for 2 hours while maintaining at 80 to 81 ° C., and then cooled to room temperature.

Into a purification tank equipped with a stirrer, 22 kg of hexane was charged, cooled to 15 ° C. with stirring, and maintained in that state. A polymerization solution was dropped here to precipitate a copolymer, and the mixture was further stirred for 30 minutes, and then the wet cake was filtered. This wet cake was returned to the container, 12 kg of hexane and 3 kg of MEK were added, and the mixture was stirred for 30 minutes, washed, and filtered. This washing of the wet cake was repeated once more. Several grams were extracted from the obtained wet cake, dried under reduced pressure at 60 ° C. or lower for 1 hour to obtain a dry powder, and each of the repeating unit composition ratios of G, Ma, and Oa of the copolymer using ¹³ C-NMR and GPC. , Mw and Mw / Mn were determined. The results are shown in Table 1.

  The remaining wet cake was dissolved in MEK and heated under reduced pressure while stirring to partially distill off light components such as MEK. Then, while adding PGMEA, further add light components and a part of PGMEA. Distillation was performed to obtain a PGMEA solution containing 25% by mass of the copolymer. The acid value of the copolymer in the obtained PGMEA solution was measured. Next, a lithographic composition was prepared by the method described above, and Eth and γ values were measured. The results are summarized in Table 1.

Example 2
A purified monomer G ₂ , a purified monomer Ma ₂ , and a purified monomer Oa ₂ were used instead of the purified monomer G ₁ , the purified monomer Ma ₁ , and the purified monomer Oa ₁ , respectively. In the same manner as in Example 1, a copolymer and a composition for lithography were obtained. Table 1 shows the composition ratios of repeating units G, Ma, and Oa of the copolymer, Mw, Mw / Mn, acid value, and Eth and γ values of the lithography composition.

Example 3
A copolymer and a composition for lithography were obtained in the same manner as in Example 1 except that purified monomer Oa ₃ was used instead of purified monomer Oa ₁ . Table 1 shows the composition ratios of repeating units G, Ma, and Oa of the copolymer, Mw, Mw / Mn, acid value, and Eth and γ values of the lithography composition.

Comparative Example 1
Use purified monomeric _{G 1,} purified monomer _{M 1,} instead of the purified monomer Oa _1, each commercial monomeric _{G 1,} commercially available monomer _{M 1,} a commercially available monomer Oa ₁ A copolymer and a lithographic composition were obtained in the same manner as in Example 1 except that. Table 1 shows the composition ratios of repeating units G, Ma, and Oa of the copolymer, Mw, Mw / Mn, acid value, and Eth and γ values of the lithography composition.

Comparative Example 2
Instead of the purified monomer G ₁ , the purified monomer M ₁ , and the purified monomer Oa ₁ , a commercially available monomer G ₂ , a commercially available monomer M ₂ , and a commercially available monomer Oa ₂ are used. A copolymer and a lithographic composition were obtained in the same manner as in Example 1 except that. Table 1 shows the composition ratios of repeating units G, Ma, and Oa of the copolymer, Mw, Mw / Mn, acid value, and Eth and γ values of the lithography composition.

  Using the lithography composition containing the copolymer produced according to the present invention and evaluating the lithography properties under dry and immersion conditions by ArF exposure, bromothymol blue was used as an indicator in any lithography condition, and an aqueous NaOH solution was used. By using a copolymer having an acid value of 0.01 mmol / g or less obtained by titration, a high γ value, which is a parameter representing the resolution contrast, was obtained. From this result, it can be seen that the lithography composition containing the copolymer produced according to the present invention is excellent in the resolution performance of the fine pattern.

Claims (5)

Copolymer including at least a repeating unit (A) having a structure in which an alkali-soluble group is protected with an acid dissociable, dissolution inhibiting group, a repeating unit (B) having a lactone structure, and a repeating unit (C) having an alcoholic hydroxyl group A method for producing a coalescence, comprising at least one kind selected from a monomer that gives a repeating unit (A), a monomer that gives a repeating unit (B), and a monomer that gives a repeating unit (C) After the step of contacting with an ion exchange resin in a state dissolved in an organic solvent, the resulting copolymer is dissolved in a solvent by being subjected to copolymerization, and then an alkali metal hydroxide using bromothymol blue as an indicator. the acid value was determined by the method of neutralization titration with a solution containing, in the following 0.01 mmol / g, and the state in which the monomer was dissolved in ethyl acetate, Do contain additives Contacting both by stirring after switching on the 20-25 ° C. water, separated to copolymer for semiconductor lithography, characterized by a value lower than when subjected to copolymerization after undergoing one step Manufacturing method. The acid dissociable, dissolution inhibiting group of the repeating unit (A) has the formula (L1)

{In Formula (L1), o is a binding site as an acid dissociable, dissolution inhibiting group, R ₁₃ and R ₁₄ are each independently a hydrocarbon group having 1 to 4 carbon atoms, and R ₁₅ is a carbon number 1 to 12 R ₁₅ may be bonded to R ₁₃ or R ₁₄ to form a ring. }
Or formula (L2)
{In Formula (L2), o is a bonding site as an acid dissociable, dissolution inhibiting group, R ₁₆ and R ₁₇ are each independently a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and R ₁₈ is a carbon number. Represents a hydrocarbon group of 1 to 12, and R ₁₆ may combine with R ₁₇ or R ₁₈ to form a ring. }
The manufacturing method of the copolymer for semiconductor lithography of Claim 1 chosen from the structure represented by these. The repeating unit (A) is represented by the formula (A)
{In Formula (A), R ₁₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms that may be substituted by a fluorine atom, and R ₁₁ represents 6 to 6 carbon atoms that may include an oxygen atom or a sulfur atom. 12 represents an alicyclic hydrocarbon group, n represents an integer of 0 or 1, and R ₁₂ represents an acid dissociable, dissolution inhibiting group represented by the formula (L1) or (L2). }
The manufacturing method of the copolymer for semiconductor lithography of Claim 1 which is a structure represented by these. The repeating unit (B) is represented by the formula (B)
[In the formula (B), R ₂₀ may be a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and R ₂₁ may contain a single bond, an oxygen atom or a sulfur atom. An alicyclic hydrocarbon group having 5 to 12 carbon atoms, L ₃ is a formula (L3)
{In Formula (L3), R _{22 to} R ₂₉ are single bonds in which one or two of them are bonded to R ₂₁ , and the rest represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group. , M represents an integer of 0 or 1. }, L ₃ is bonded to R ₂₁ with 1 or 2 single bonds. ]
The manufacturing method of the copolymer for semiconductor lithography of Claim 1 which is a structure represented by these. The repeating unit (C) is represented by the formula (C)
{In Formula (C), R ₃₃ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by a fluorine atom, and R _{34 to} R ₃₆ each independently represents a hydrogen atom or a hydroxyl group. , At least one of R _{34 to} R ₃₆ is a hydroxyl group. }
The manufacturing method of the copolymer for semiconductor lithography of Claim 1 which is a structure represented by these.