JP5646149B2 - Copolymer for photoresist, production method and storage method thereof - Google Patents

Description

  The present invention relates to a photoresist material and a photoresist composition that are suitably used in a microfabrication technique in a manufacturing process of a semiconductor element, an ultrafine photolithography process such as manufacture of a VLSI and a high-capacity microchip, and other photofabrication processes. And a method for producing a polymer compound useful as a base polymer, and a photoresist material and a photoresist composition obtained by the production method.

In the field of microfabrication typified by the manufacture of semiconductor integrated devices such as VLSI, the formation of ultrafine patterns in the submicron to quarter micron region is required with the trend of ultrahigh integration of integrated circuits. Accordingly, in order to obtain a higher degree of integration of the exposure wavelength from g-line to i-line, recently, a light source having a shorter wavelength than ArF excimer laser (wavelength 193 nm), F ₂ excimer laser (wavelength 157 nm) or the like is used. There is a need for a lithography technique capable of fine processing at a level of about 50 nm or less by combining with a technique such as lithography. The base polymer used in such a radiation-sensitive resin composition suitable for photolithography using an excimer laser has a molecular weight, control of molecular weight distribution, stability, uniformity of copolymer composition distribution, Higher quality such as reduction of the amount of impurities such as ultra high molecular weight components, low molecular weight components and the like is required.

  By the way, in the production of a copolymer, the quality of the resin may be deteriorated due to a change with time, and various studies have been made. For example, in a positive photoresist containing a quinonediazide sulfonic acid halide, it has been proposed to store the quinonediazide sulfonic acid halide in a low temperature dark place because it is easily decomposed (for example, Patent Document 1). It has also been proposed to store the color resist composition in a light-shielded state and in a specific temperature range of −5 ° C. to 25 ° C. (for example, Patent Document 2). Further, it has been proposed to use a special package for storing a liquid composition such as a photoresist (for example, Patent Document 3).

  However, there is still a demand for the development of a method for producing a copolymer including a storage step that can maintain the quality of the resin for a long period of time.

JP 9-204052 A JP 2003-149801 A Special table 2008-539145

  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 copolymer for a photoresist that can prevent aging of a lactone structure and an acid group-containing resin that easily deteriorate during storage. It is to provide a manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have attributed to the deterioration of quality due to aging of a resin having a specific structure stored in a powder state, and the quality in the storage process. Under the assumption that one cause of deterioration may be hydrolysis of acid-decomposable groups or lactone structures catalyzed by moisture in the storage resin and a small amount of acid in the resin, It has been found that the deterioration of the resin quality can be suppressed by the process of keeping the coalescence in a solution state, and the present invention has been completed.

  That is, the present invention relates to a method for producing a copolymer for photoresist comprising a repeating unit having a lactone structure and a repeating unit having an acidic group, wherein the copolymer is kept in a solution state by a hydroxy group-free solvent. The manufacturing method of the copolymer for photoresists including the preservation | save process containing is provided.

  According to another aspect, the present invention provides a method for preserving a copolymer for a photoresist comprising a repeating unit having a lactone structure and a repeating unit having an acidic group, wherein the copolymer contains no hydroxy group. The preservation method includes keeping the solution in a solvent state.

  According to another aspect, the present invention provides a photoresist copolymer comprising a repeating unit having a lactone structure and a repeating unit having an acidic group, wherein the copolymer is a solution containing a hydroxy group-free solvent. The present invention provides a photoresist copolymer that is kept in a state.

  According to the present invention, it is possible to prevent aging of the lactone structure and acidic group-containing resin that are likely to deteriorate during storage, and to maintain the resin molecular weight and composition constant even after long-term storage. .

  Hereinafter, embodiments of the present invention will be described in detail.

Copolymer Structure The copolymer obtained by the production method of the present invention contains a repeating unit having a lactone structure and a repeating unit having an acidic group. Note that the lactone structure and the acidic group may exist on the same repeating unit or on different repeating units. Further, as a specific structure, for example, those having the following structural formulas are preferable.

Repeating Unit Having Lactone Structure According to a preferred embodiment of the present invention, the repeating unit having a lactone structure has a structure represented by the formula (A).

式（Ａ）中、Ｒ_１０は水素原子、または、フッ素原子が置換しても良い炭素数１〜４の炭化水素基を表し、具体的には、水素原子、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｉ−ブチル基、トリフルオロメチル基等の炭素数１〜４のアルキル基を挙げることができ、好ましくは、水素原子、メチル基、トリフルオロメチル基である。Ｒ_１１は式（ａ）で表されるラクトン構造含有基を表す。

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- Examples thereof include alkyl groups having 1 to 4 carbon atoms such as propyl group, i-propyl group, n-butyl group, i-butyl group and trifluoromethyl group, preferably hydrogen atom, methyl group and trifluoromethyl. It is a group. R ₁₁ represents a lactone structure-containing group represented by the formula (a).

式（ａ）中、Ｒ_１２〜Ｒ_１９は、いずれか１つが、Ｒ_１１としての結合部位を有する単結合を表し、残りのＲ_１２〜Ｒ_１９は、水素原子、または、炭素数１〜４の炭化水素基若しくはアルコキシ基を表すか、または、いずれか１つが、Ｒ_１１としての結合部位を有し、他のＲ_１２〜Ｒ_１９のいずれか１つまたは２つと結合して炭素数５〜１５の脂環を形成する、酸素原子若しくは硫黄原子を含んでも良い炭素数３〜１４の炭化水素基を表し、残りのＲ_１２〜Ｒ_１９は、いずれか１つまたは２つが前記炭素数５〜１５の脂環を形成するための単結合を表し、その残りは、水素原子、または、炭素数１〜４の炭化水素基若しくはアルコキシ基を表す。脂環の具体例としては、シクロペンタン環、シクロヘキサン環、ノルボルナン環、７−ｏｘａ−ノルボルナン環、７−ｔｈｉａ−ノルボルナン環、テトラシクロ［４.４.０.１^2,5.１^7,10］ドデカン環等、好ましくは、ノルボルナン環、７−ｏｘａ−ノルボルナン環を挙げることができる。炭素数１〜４の炭化水素基の具体例としては、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、およびｉ−ブチル基等を挙げることができ、炭素数１〜４のアルコキシ基の具体例としては、メトキシ基、エトキシ基等を挙げることができる。また、ｍは０または１の整数を表す。

Wherein _{(a), R} 12 ~R ₁₉ is any one of _a single bond with a binding site of the _{R 11,} the remainder of _R 12 _{to R 19} is a hydrogen atom or a 1 to 4 carbon atoms Or any one of them has a binding site as R ₁₁ , and is bonded to any one or two of other R _{12 to} R ₁₉ to form a carbon atom having 5 to 5 carbon atoms. Represents a hydrocarbon group having 3 to 14 carbon atoms which may contain an oxygen atom or a sulfur atom and forms 15 alicyclic rings, and the remaining R _{12 to} R ₁₉ are any one or two of which have 5 to 5 carbon atoms. 15 represents a single bond for forming an alicyclic ring, and the remainder represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group. Specific examples of the alicyclic ring, a cyclopentane ring, a cyclohexane ring, norbornane ring, 7-oxa norbornane ring, 7-thia norbornane ring, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] A dodecane ring etc., Preferably, a norbornane ring and a 7-oxa-norbornane ring can be mentioned. Specific examples of the hydrocarbon group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and an i-butyl group. Specific examples of the 1-4 alkoxy group include a methoxy group and an ethoxy group. M represents an integer of 0 or 1.

Any one of R ₁₂ to R ₁₉ is a single bond with a binding site of the _{R 11,} the remainder of _R 12 _{to R 19} is a hydrogen atom or a hydrocarbon group or an alkoxy group having 1 to 4 carbon atoms Particularly preferred examples of the lactone structure to be represented include a γ-butyrolactone structure and a δ-valerolactone structure. Any one of R ₁₂ to R ₁₉ is has a binding site as _{R 11,} form a alicyclic of 5 to 15 carbon atoms bonded to one or two and one of the other _R 12 _{to R 19,} contain an oxygen atom or a sulfur atom represents an hydrocarbon group having a carbon number of 3 to 14, the remainder of R ₁₂ to R ₁₉ is any one or two to form an alicyclic ring of said 5 to 15 carbon atoms As a particularly preferred example of a lactone structure representing a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group , the remainder is a 1,3-cyclohexanecarbolactone structure, 2,6- Examples thereof include a norbornane carbolactone structure, a 7-oxa-2,6-norbornane carbolactone structure, and a 4-oxa-tricyclo [5.2.1.0 ^2,6 ] decan-3-one structure.

Repeating Unit Having an Acidic Group According to a preferred embodiment of the present invention, the repeating unit having an acidic group can include a repeating unit having a substituent having _a pK _{a of} 10 or less, preferably a substitution of pK _{a of} 6 or less. And a repeating unit having a phenolic hydroxy group. More preferably, a repeating unit having at least one selected from the group consisting of a carboxyl group, a phenol group, a naphthol group, a thiol group, and a sulfo group can be mentioned, and even more preferably, a repeating unit having a carboxyl group Can be mentioned. Examples of the repeating unit having a carboxyl group include repeating units derived from acrylic acid, methacrylic acid, maleic anhydride, or a mixture thereof. When the acidic group is a substituent of the pK _a of about above range, the effect of moisture the acidity and the atmosphere, the effect of saving increases in solution for the acid-decomposable group and lactone is decomposed .

Other Repeating Units According to a preferred embodiment of the present invention, the copolymer can further contain other repeating units in addition to the above repeating units. Other repeating units include, for example, a repeating unit that becomes alkali-soluble by an acid, a repeating unit having a polar group-containing alicyclic group, a repeating unit having a cyclic ether structure, a repeating unit having an acid-stable dissolution inhibiting structure, and the like. Arbitrary repeating units can be mentioned. Preferably, it includes a repeating unit that becomes alkali-soluble by an acid or a repeating unit having a polar group-containing alicyclic group.
Terminal structure According to a preferred embodiment of the present invention, the copolymer comprises a known terminal structure. Usually, a radical structure generated from a radical polymerization initiator is included as a polymerization initiation terminal. When a chain transfer agent is used, a radical structure generated from the 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 a polymerization initiation terminal, and when disproportionation termination, one side can contain a polymerization initiation terminal and the other can contain a monomer-derived terminal structure. . 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 at the other end. A plurality of these initiation reactions and termination reactions may occur in one polymerization reaction. In this 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.

Molecular Weight and Dispersibility If the weight average molecular weight (hereinafter sometimes referred to as “Mw”) is too high, the copolymer of the present invention has low solubility in a resist solvent or an alkali developer, whereas it is too low. Mw is preferably in the range of 1,000 to 50,000, more preferably in the range of 1,500 to 30,000, and 2,000 because the coating film performance of the resist is deteriorated. It is even more preferable that it is in the range of ˜20,000, and it is particularly preferable that it is in the range of 3,000 to 15,000. In addition, if the molecular weight distribution is too wide or too narrow, a desired pattern shape may not be obtained in the lithography process, so the dispersity (hereinafter sometimes referred to as “Mw / Mn”) is 1.0-5. Is preferably within the range of 1.0, more preferably within the range of 1.0 to 3.0, even more preferably within the range of 1.2 to 2.5, and 1.4 to It is particularly preferable that it is within the range of 2.0.

Solvent for forming a coating film The solvent for forming a coating film is not particularly limited as long as it can dissolve each component constituting the lithography composition to form a uniform solution. Can be used as one single solvent or two or more mixed solvents. Since it is excellent in solubility, a solvent having at least one polar group selected from a ketone bond, an ester bond, an ether bond and a hydroxy group is preferable. Among them, a solvent having a boiling point of 110 to 220 ° C. at normal pressure is particularly preferable because the evaporation rate is moderate in baking after spin coating and the film forming property is excellent. Specific examples of such solvents include solvents having a ketone bond such as methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone and cyclohexanone, solvents having an ether bond and a hydroxy group such as propylene glycol monomethyl ether and propylene glycol monoethyl ether. A solvent having an ether bond and an ester bond such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate and ethyl 3-ethoxypropionate, an ester bond such as methyl lactate and ethyl lactate (EL) and a hydroxy group. And a solvent having an ester bond such as γ-butyrolactone. Particularly preferred is a solvent containing PGMEA.

Copolymer solution The copolymer solution for lithography comprises the above copolymer and a solvent for forming a coating film. Further, an additive necessary for use as a lithography composition may be included.

  The concentration of the copolymer contained in the solution can be appropriately set so as to obtain a viscosity that provides an appropriate film thickness when applied to a substrate. It can also be set relatively high as long as the copolymer can be dissolved so that it can be mixed with other solvents not included in the solution, other lithographic copolymer solutions, and the like. Usually, the copolymer concentration in the solution is adjusted to be in the range of 2 to 60% by mass, preferably 3 to 50% by mass, particularly preferably 5 to 35% by mass.

  As an example of the case where an additive necessary for use as a lithography composition is contained, when the lithography composition is a chemically amplified resist composition, a radiation-sensitive acid generator, acid diffusion to a portion not exposed to radiation An acid diffusion inhibitor, such as a nitrogen-containing organic compound, for preventing the above, and other additives as necessary.

  The radiation sensitive acid generator can be appropriately selected from those proposed so far as radiation sensitive acid generators for chemically amplified resists. Examples include onium salts such as iodonium salts and sulfonium salts, oxime sulfonates, diazomethanes such as bisalkyl or bisarylsulfonyldiazomethanes, nitrobenzyl sulfonates, imino sulfonates, 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. The radiation sensitive acid generator is usually used in an amount 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 acid diffusion inhibitor can be appropriately selected from those previously 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 acid diffusion inhibitor is usually used in the range of 0.01 to 5.0 parts by mass with respect to 100 parts by weight of the copolymer.

  Other additives mentioned above include organic carboxylic acids and phosphorus oxo acids for the purpose of improving the sensitivity of the acid generator, preventing the resist pattern from deteriorating, improving the resist pattern shape, and stability, and improving the performance of the resist film. Additive resins, surfactants to improve coatability, dissolution inhibitors, plasticizers, stabilizers, colorants, antihalation agents, dyes, and other compounds commonly used as resist additives as needed Can be added as appropriate. 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.

Method for Producing Copolymer The production method of the present invention is a method for producing a copolymer for photoresist comprising a repeating unit having a lactone structure and a repeating unit having an acidic group, and the copolymer does not contain a hydroxy group. It includes a storage step including keeping the solution in a solvent state. The production method of the present invention can be carried out using a monomer, a solvent, a polymerization initiator, a chain transfer agent, and other additives that can give the following repeating units, and includes the following steps. it can.

Polymerization Step According to a preferred embodiment of the present invention, the polymerization step of the monomer capable of providing a repeating unit having a lactone structure, a repeating unit having an acidic group, and further another repeating unit includes radical polymerization and cationic polymerization. All known polymerization methods such as living anionic polymerization and ring-opening polymerization can be applied.

  For example, after polymerizing a monomer having an alkali-soluble structure and then protecting the alkali-soluble substituent in the alkali-soluble structure with an acid-dissociable protecting group, the compound having the alkali-soluble group is polymerized as it is. It is possible to introduce an acid dissociable protecting group by reacting with a compound that gives a substituent that does not dissolve in an alkali such as vinyl ether or halogenated alkyl ether under an acid catalyst (acetalization reaction). it can. By protecting an alkali-soluble substituent with an acid-dissociable, alkali-insoluble protective group, performance as a photoresist that exhibits alkali-solubility with an acid can be exhibited. Examples of the acid catalyst used in the reaction include p-toluenesulfonic acid, trifluoroacetic acid, and strongly acidic ion exchange resin.

  In the present invention, a known polymerization apparatus can be used as the polymerization apparatus. As an apparatus that can be industrially mass-produced, it is preferable to use a polymerization tank equipped with at least a canister for supplying a heat medium, a stirring blade, and a condenser. The material is preferably a glass-lined container because it is necessary to avoid contamination of the metal and because it has high thermal conductivity and safety. The stirring blade is preferably a full blade such as a three-blade retracted blade, a partial blade such as a twin star blade manufactured by Shinko Environmental Solution Co., Ltd., a full zone blade manufactured by Shinko Environmental Solution Co., Ltd., or a bend leaf blade manufactured by Yako Sangyo Co., Ltd. Due to the high stirring efficiency, full blades such as full zone blades and bend leaf blades are particularly preferable.

  The polymerization of the present invention is preferably performed by a so-called dropping method in which a monomer (monomer solution) and a polymerization initiator are dropped into a heated solvent. A part of the monomer may be included in the heated solvent in advance. In addition, a plurality of liquids having different monomer compositions, polymerization initiator concentrations, and chain transfer agent concentrations are dropped, for example, the monomer composition, monomer, polymerization initiator, and chain dropped along with the dropping time. The composition ratio of the transfer agent may be changed.

  Among the dropping methods, a monomer is dissolved in a solvent together with a polymerization initiator as needed, and a mixed dropping method in which the monomer is dropped into a heated solvent to polymerize, and the monomer and the polymerization initiator are respectively required. A so-called independent dropping method in which a polymer is dissolved in a solvent and dropped separately into a heated solvent can be employed. However, the mixed dripping method causes microgel generation because there is an opportunity to come into contact with low concentration radicals in a state where the concentration of unreacted monomer is high in the dropping liquid storage tank before dropping into the polymerization system. High polymer is easily formed. On the other hand, since the independent dropping method does not coexist with the polymerization initiator in the dropping liquid storage tank, a high polymer is not generated. Therefore, the independent dropping method is particularly preferable.

  In the independent dropping method, the monomer solution and the initiator solution can be premixed immediately before the polymerization tank, but a high polymer may be formed before the dropping, so that the polymer solution and the initiator solution are separated. It is particularly preferable to add each of them independently from the storage tank. The supply rates of the monomer solution and the initiator solution can be set independently so that a copolymer having a desired molecular weight distribution can be obtained. It is also possible to obtain a copolymer having a wide molecular weight distribution from narrow dispersion to polydispersity with good reproducibility by changing either one or both of the two liquid supply rates. For example, if the supply amount of the initiator solution in the first reaction period is decreased and the supply amount of the initiator solution is increased in the second reaction period, a copolymer having a relatively high molecular weight is formed in the first reaction period with a low radical concentration. A dispersed copolymer can be obtained. Each feed rate can be varied continuously or stepwise.

  In the dropping method, the amount of the polymerization solvent (hereinafter sometimes referred to as the initial tension solvent) to be initially placed in the reaction tank is not less than the minimum amount capable of stirring, but if it is more than necessary, it is supplied. This is not preferable because the amount of the monomer solution that can be produced decreases and the production efficiency decreases. Usually, for example, a volume ratio of 1/30 or more, preferably 1/20 to 1/2, with respect to the final charge amount (that is, the total amount of the initial tension solvent and the dropped monomer solution and initiator solution), Particularly preferably, it is selected from the range of 1/10 to 1/3. A part of the monomer may be mixed in advance with the initial tension solvent.

  From the standpoint of productivity, the concentration of the monomer and the polymerization initiator in the dropping liquid is preferably higher. In particular, when the polymerizable monomer or polymerization initiator is liquid, it can be supplied as it is without dissolving in the solvent, but the polymerizable monomer or polymerization initiator is viscous liquid or solid. In such a case, it is necessary to use it dissolved in a solvent. When the polymerizable monomer or the polymerization initiator is dissolved in a solvent and used, if the concentration is too high, the solution viscosity becomes high and the operability is poor. Further, when the polymerizable monomer or the polymerization initiator is a solid, it may be precipitated, or it may take a long time to diffuse in the polymerization system, and a high polymer may be easily generated. Therefore, it is preferable to select a concentration in which each monomer and the polymerization initiator are sufficiently dissolved, do not precipitate during the supply, and easily diffuse in the polymerization system within a viscosity range that does not cause a problem in the supply operation. The specific concentration varies depending on the combination of the solute and the solvent of each solution, but the total concentration of all monomers and the polymerization initiator concentration are usually 5 to 60% by mass, preferably 10 to 50% by mass, respectively. It is good to prepare so that it may become the range.

  The polymerization temperature can be appropriately selected depending on 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 preferable to select a range of 40 to 160 ° C., particularly preferably 60 to 120 ° C.

In order to make the molecular weight of the copolymer and the copolymer composition in the case of copolymerization as intended, it is necessary to precisely control the polymerization temperature. The polymerization reaction is generally an exothermic reaction, and the polymerization temperature tends to increase due to the polymerization reaction, so that it is difficult to control to a constant temperature. If the polymerization temperature rises too much, the polymerization reaction may become uncontrollable and runaway. Therefore, in the present invention, the polymerization solvent contains at least one compound having a boiling point close to the target polymerization temperature, and the polymerization temperature is equal to or higher than the initial boiling point at the polymerization pressure of the component contained as the polymerization solvent. It is preferable to set to. According to this method, an increase in the polymerization temperature can be suppressed by the latent heat of vaporization of the polymerization solvent. Specific examples of such compounds include water, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, cyclohexanone and other ketones; methanol, ethanol, isopropanol and other alcohols; ethylene glycol monomethyl ether, ethylene Ether alcohols such as glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether; esters such as methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, methyl propionate, methyl lactate and ethyl lactate; Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate Ether esters such as tate and propylene glycol monoethyl ether acetate; ethers such as tetrahydrofuran, 1,4-dioxane and ethylene glycol dimethyl ether; aromatic hydrocarbons such as toluene and xylene; N, N-dimethylformamide, acetonitrile and the like Can be mentioned. From the solubility and boiling point of monomers, polymerization initiators, chain transfer agents and copolymers, acetone, methyl ethyl ketone, methyl isobutyl ketone, isopropanol, propylene glycol monomethyl ether, methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, propion Methyl acid, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, toluene and acetonitrile are preferred. These can be used individually or in mixture of 2 or more types. The ethylene glycol monobutyl ether, 3-methoxy-3-methyl-1-butanol, 3-methoxy-3-methyl-1-butyl acetate, ethyl 3-ethoxypropionate, .gamma.-butyrolactone, diethylene glycol dimethyl ether, N- A monomer, a polymerization initiator, a chain transfer agent, and a copolymer, such as methyl pyrrolidone and dimethyl sulfoxide, which have high solubility, may be used in combination with a high boiling point compound.

  As the polymerization initiator used for the polymerization, 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′-azobis (2-methylpropionate), Examples thereof include dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile), 4,4′-azobis (4-cyanovaleric acid), and the like. Specific examples of peroxides include decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, succinic acid peroxide, tert-butylperoxy-2-ethyl Hexanoate, tert-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate and the like can be mentioned. An azo compound is particularly preferable from the viewpoint of handling safety. These can be used alone or in combination. The amount of the polymerization initiator used is selected according to the production conditions such as the target Mw, the raw material monomer, the polymerization initiator, the chain transfer agent, the type and composition ratio of the solvent, the polymerization temperature, and the dropping method. 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 variety can be selected from known thiol compounds. Specific examples include t-dodecyl mercaptan, mercaptoethanol, mercaptoacetic acid, mercaptopropionic acid, and the like. The amount of the chain transfer agent used is selected according to the production conditions such as the target Mw, the raw material monomer, the polymerization initiator, the chain transfer agent, the type and composition ratio of the solvent, the polymerization temperature, and the dropping method. be able to. The chain transfer agent 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.

Polymerization Reaction Stopping Step According to a preferred embodiment of the present invention, the production method can include a step of stopping the polymerization reaction by cooling or adding a heavy metal after supplying the entire amount of the monomer solution. For example, it is preferable to quench the polymerization system immediately after supplying the entire amount of the monomer solution. By rapidly cooling, the polymerization reaction can be stopped immediately, and the production of a polymer having a large deviation in monomer composition can be prevented. Alternatively, the polymerization reaction may be stopped by addition of heavy metal, but it is more preferable to stop the polymerization reaction by rapid cooling because a removal process of heavy metal is required thereafter.

Purification Step According to a preferred embodiment of the present invention, the production method can include a step of purifying the copolymer solution by a known method such as reprecipitation in a solvent after polymerization. For example, the reaction solution is dropped into a large amount of toluene to precipitate a produced resin, and separated from a toluene solvent containing residual monomers and low molecular weight substances. Subsequently, the operation of dissolving the resin in methanol and adding toluene again is repeated several times to purify the resin. By such a series of operations, by extracting and removing low molecular weight components such as unreacted monomers and oligomers such as monomers and polymerization initiators from the copolymer solution in a solvent, the performance of the resin is improved, In the semiconductor manufacturing process, it is possible to improve the pattern shape, improve the sensitivity, suppress the generated defects, and reduce the defect rate.

Demetallization Step According to a preferred embodiment of the present invention, the production method can include a step of filtering the copolymer solution with a filter to remove metal ions and the like. Preferably, demetallation is performed after the above purification step. By removing metal ions, etc., from the purified copolymer solution using a demetallizing filter, it is possible to improve sensitivity in the semiconductor manufacturing process, suppress defects that occur, and reduce the defect rate. it can.

  Examples of the filter include filter aids such as diatomaceous earth, depth filters made of cellulose, polyolefins such as polyethylene and polypropylene, polar group-containing resins such as polyamide, polyester, and polyacrylonitrile, and fluorine-containing resins such as fluorinated polyethylene. A membrane filter made of a material selected from Examples of depth filters include Zeta Plus 40QSH, Zeta Plus 020GN, etc. manufactured by Cuno. Examples of membrane filters include: Nihon Entegris micro guards, polyethylene filters such as Optimizer D, Nihon Pole Ultipleat P-Nylon 66, Ulchipore N66, Cuno Photoshield, and Electropore IIEF nylon. And filters made of fluorinated polyethylene such as Nihon Pole Penflon. The filtration accuracy of the filter is usually 1 μm or less, preferably 0.5 μm or less, particularly preferably 0.05 μm or less. These filters may be used alone or in combination of two or more.

Storage Step The production method of the present invention includes a storage step including maintaining a copolymer containing a repeating unit having a lactone structure and a repeating unit having an acidic group in a solution state with a hydroxy group-free solvent. It is preferable that the copolymer has undergone the above purification step and metal removal step. The hydroxy group-free solvent used in the storage step is at least one selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and hexane. Examples of the solvent include at least one solvent selected from the group consisting of methyl ethyl ketone, propylene glycol methyl ether acetate, hexane, and cyclohexanone. By using a hydroxy group-free solvent, the degradation of the resin during storage can be suppressed by suppressing the decomposition reaction of the lactone structure and acid-decomposable groups contained in the copolymer even in an environment where acids derived from acidic groups are present. It is thought that it can be suppressed.

  According to a preferred embodiment of the present invention, the water content of the copolymer maintained in the solution state is 500 ppm or less, more preferably 400 ppm or less, and even more preferably 300 ppm or less. When the water content is in the above range, deterioration of the resin during storage can be further suppressed.

  According to a preferred embodiment of the present invention, the storing step further includes maintaining a sealed state. In order to maintain a sealed state, it is preferable to use a known storage method, for example, a known package. Specifically, light-shielded glass containers, Teflon (registered trademark) containers (including metal or plastic containers coated with Teflon), high-density polyethylene containers with few additives, commercially available chemical-resistant containers for semiconductor-related products, It is preferable to store the solution using a chemical drum or the like. By maintaining such a sealed state, it is possible to more effectively prevent external moisture from being mixed and maintain a dehydrated state.

  According to a preferred embodiment of the present invention, the storage step may further comprise maintaining a low temperature state, for example, preferably 20 ° C. or lower, more preferably 10 ° C. or lower, and further preferably 5 ° C. or lower. By maintaining such a low temperature state, quality degradation due to thermal decomposition can be effectively suppressed.

  According to a preferred embodiment of the present invention, the storage step is in a light-shielded state, for example, preferably a state where the transmittance of light of 500 nm or less is 10% or less, more preferably, the transmittance of light of 500 nm or less is 5% or less, Further, it may further include maintaining a state where the transmittance of light of 400 nm or less is 10% or less, more preferably, the transmittance of light of 400 nm or less is 5% or less. By maintaining such a light-shielding state, the decomposition reaction due to ultraviolet rays can be effectively suppressed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

In addition, the symbol used in the following example has the following meaning.
Lactone structure G: Repeating unit derived from γ-butyrolactone methacrylate Monomer G: γ-butyrolactone methacrylate Ga: Repeating unit derived from γ-butyrolactone acrylate Monomer Ga: γ-butyrolactone acrylate
Acid dissociable, dissolution inhibiting group M: repeating unit derived from 2-methyl-2adamantyl methacrylate Monomer M: 2-methyl-2adamantyl methacrylate Ma: repeating unit derived from 2-methyl-2adamantyl acrylate Monomer Ma: 2 -Methyl-2 adamantyl acrylate
Alcohol structure O: repeating unit derived from 3-hydroxy-1-adamantyl methacrylate Monomer O: repeating unit derived from 3-hydroxy-1-adamantyl methacrylate Oa: repeating unit derived from 3-hydroxy-1-adamantyl acrylate monomer Oa: 3- Hydroxy-1-adamantyl acrylate
Acid group MA: repeating unit derived from methacrylic acid (carboxyl group pK _a : 4.26)
AA: repeating unit derived from acrylic acid (carboxyl pK _a : 4.25)
Solvent MEK: Methyl ethyl ketone THF: Tetrahydrofuran PGMEA: Propylene glycol monomethyl ether acetate CHON: Cyclohexanone

Inspection Method The following GPC, carbon 13 NMR, neutralization titration, GC, and moisture inspection methods are as follows.

GPC : Measurement of Mw and Mw / Mn of copolymer Measured by GPC. The analysis conditions are as follows.
Equipment: Tosoh GPC8220
Detector: differential refractive index (RI) detector Column: Showa Denko KF-804L (× 3)
Sample: About 0.02 g of the copolymer powder was dissolved in about 1 ml of tetrahydrofuran to prepare a sample for measurement. The injection amount into GPC was 60 μl.

Carbon 13 NMR : measurement of copolymer repeating unit composition and detection of reaction product Apparatus: AV400 manufactured by Bruker
Sample: Prepared by dissolving about 1 g of copolymer powder and 0.1 g of acetylacetone chromium in 0.5 g of MEK and 1.5 g of heavy acetone.
Measurement: 40 ° C., measurement tube diameter 10 mm, integration number 10,000 times The composition of the copolymer was expressed with the total of components detectable by the carbon 13 NMR spectrum as 100%. (Acrylic acid and methacrylic acid are excluded because they cannot be detected)

Neutralization titration : Measurement of the acid value of the copolymer Accurately measure 1 g of copolymer solids, mix 30 g of THF and the indicator bromothymol blue, and add 0.1 wt% (= 0.025 N) of NaOH water. And titrated. The end point was the point when the color changed from green to slightly blue. The acid value was calculated from the following formula (1).
Acid value (mmol / g) = BxF / A / M Formula (1)
B: NaOH water dropping amount F: NaOH water factor A: Copolymer measurement value M: Concentration of copolymer

GC : measurement of residual solvent and solvent composition Apparatus : GC-1700 manufactured by Shimadzu
Detector: FID detector Column: TC-1 column manufactured by GL Sciences Sample: Dissolved in THF, and ethylbenzene was added as an internal standard substance.

Moisture : measured by the Karl Fischer method.
Apparatus: Karl Fischer micro moisture measuring device AQ-7 manufactured by Hiranuma Sangyo Co., Ltd.

Synthesis example 1
Monomer composition ratio (molar ratio): G / Ma / Oa / AA = 38/38/19/5
First, MEK2657g, monomer G646g, monomer Ma836g, monomer Oa422g, and acrylic acid 36g were added and dissolved in the container to prepare a uniform monomer solution. In a separate container, 200 g of MEK and 69 g of dimethyl 2,2′-azobisisobutyrate (MAIB) were dissolved to prepare a uniform initiator solution.

  Next, 1600 g of MEK was charged into a reaction vessel equipped with a stirrer and a cooler to form a nitrogen atmosphere, and then heated to 79 ° C. The monomer solution and the initiator solution kept at room temperature (about 25 ° C.) were dropped into a reaction vessel kept at 79 to 81 ° C. separately at a constant rate for 4 hours using a metering pump. After completion of the dropwise addition, the mixture was further aged for 2 hours while maintaining at 79 to 81 ° C., and then cooled to room temperature, and the polymerization solution was taken out.

  The resin solution was reprecipitated with n-hexane, and the precipitated resin powder was filtered. By this step, the unreacted monomer and the polymerization initiator were removed. The resin powder was again washed twice with an n-hexane / MEK mixed solvent.

A part of the resin powder was sampled and dried under reduced pressure to obtain a dry resin powder. This dry resin powder was analyzed by the above inspection method. The analysis results were as follows.
Molecular weight (GPC): Mw = 10,230, Mw / Mn = 2.15
Composition (carbon 13 NMR): G / Ma / Oa = 41/39/20
Acid value (neutralization titration): 0.25 mmol / g
Residual solvent (GC): hexane 5%, MEK 1%

Most of the remaining resin powder was dissolved in MEK to obtain a MEK / hexane solution of the resin. The diluted MEK / hexane solution of the resin thus obtained was passed through an N66 filter (0.04 μm diameter, manufactured by Nihon Pall) to remove solid impurities. In this state, a part of the solution was sampled and analyzed. The analysis results were as follows.
Resin concentration: 13.1%.
Solvent composition (GC): MEK 87.0%, hexane 13.0%, residual moisture 150 ppm

Then, it moved to the reactor, the PGMEA solvent was injected | thrown-in, and PGMEA was added, removing a low boiling point component under reduced pressure at 50 degrees C or less, and it was set as the 25% PGMEA solution. The analysis results of the resin PGMEA solution were as follows.
Solvent composition (GC): PGMEA 99.98%, MEK 0.02%, residual moisture 80ppm

Synthesis example 2
Monomer composition ratio: Ga / M / O / MA = 38/38/19/5
The synthesis was performed in the same procedure as in Synthesis Example 1 except that the monomer composition ratio was as described above. In addition, MEK2868g, monomer Ga593g, monomer M889g, monomer O448g, and methacrylic acid 43g were added and dissolved in the container, and the uniform monomer solution was prepared.

The dry resin powder was analyzed in the same manner as in Synthesis Example 1. The analysis results were as follows.
Molecular weight (GPC): Mw = 10,650, Mw / Mn = 2.03
Composition (carbon 13 NMR): Ga / M / O = 40/40/20
Acid value (neutralization titration): 0.25 mmol / g
Residual solvent (GC): hexane 5%, MEK 1%

The analysis results of the finally obtained resin PGMEA solution were as follows.
Solvent composition (GC): PGMEA 99.98%, MEK 0.02%, residual moisture 80 ppm.

Synthesis example 3
Monomer composition ratio: G / M / MA = 40/40/20
The synthesis was performed in the same procedure as in Synthesis Example 1 except that the monomer composition ratio was as described above. In addition, 1950 g of MEK, 680 g of monomer G, 936 g of monomer M, and 172 g of methacrylic acid were added and dissolved in a container to prepare a uniform monomer solution.

The dry resin powder was analyzed in the same manner as in Synthesis Example 1. The analysis results were as follows.
Molecular weight (GPC): Mw = 9750, Mw / Mn = 1.98
Composition (carbon 13 NMR): G / M = 53/47
Acid value (neutralization titration): 1.02 mmol / g
Residual solvent (GC): hexane 5%, MEK 1%

The solvent that finally dissolves the resin was cyclohexanone. The analysis results with the cyclohexanone solution were as follows.
Solvent composition (GC): cyclohexanone 99.98%, MEK 0.02%, residual moisture 150 ppm

Storage test 1
For the resin 1 prepared in Synthesis Example 1, a storage stability test was performed under the following conditions in each of a powder state and a solution state (PGMEA solution). The state of preservation was packed in a 100 ml polyethylene (HDPE) container and shielded from light by winding an aluminum foil on the outside. The storage temperatures were 20 ° C. and 5 ° C., and the periods were 3, 6 and 12 months. In addition, as an accelerated storage stability test, tests were conducted for 2, 4, 6, and 8 weeks for a total of three types of powder and solution states (MEK / hexane solution or PGMEA solution) at a storage temperature of 40 ° C.

The results of the storage stability test are shown in Table 1. The sample stored in the powder state showed an increase in molecular weight and an increase in acid value, confirming that the resin had deteriorated. On the other hand, the sample stored in the solution state showed almost no change in both molecular weight and acid amount. Moreover, in the sample preserve | saved with the PGMEA solution, what was preserve | saved at 5 degreeC had less change than what was preserve | saved at 20 degreeC.

The results of the accelerated storage stability test are shown in Table 2. In the accelerated storage stability test, as in the storage stability test, it was confirmed that the sample stored in the powder state showed an increase in molecular weight and an acid value, and the resin was deteriorated. On the other hand, both the molecular weight and the acid amount were hardly changed in the samples stored in the solution state.

  Resin 1 was stored in a powder state at 20 ° C. for 12 months, and the carbon 13 NMR spectrum of a sample in which deterioration was observed was measured. It was done. Of these peaks, the peaks at 101 ppm and 159 ppm coincided with the chemical shift of methylidene adamantane. In the sample stored at 20 ° C. for 12 months in the PGMEA solution state of Resin 1, the presence of the above-mentioned degradation product peak was not confirmed in the measurement of the carbon 13 NMR spectrum.

Storage test 2
With respect to the resin 2 produced in Synthesis Example 2, a storage stability test was performed under the following conditions in each of a powder state and a solution state (PGMEA solution). The state of preservation was packed in a 100 ml polyethylene (HDPE) container and shielded from light by winding an aluminum foil on the outside. The storage temperatures were 20 ° C. and 5 ° C., and the storage periods were 2, 4 and 6 months.

The results of the storage stability test are shown in Table 3. The sample stored in the powder state showed an increase in molecular weight and an increase in acid value, confirming that the resin had deteriorated. On the other hand, the sample stored in the solution state showed almost no change in both molecular weight and acid amount. Moreover, in the sample preserve | saved with the PGMEA solution, what was preserve | saved at 5 degreeC had less change than what was preserve | saved at 20 degreeC.

Storage test 3
With respect to the resin 3 prepared in Synthesis Example 3, a storage stability test was performed under the following conditions in each of a powder state and a solution state (CHON solution). The state of preservation was packed in a 100 ml polyethylene (HDPE) container and shielded from light by winding an aluminum foil on the outside. The storage temperature was 20 ° C., and the storage period was 2, 4, and 6 months.

The results of the storage stability test are shown in Table 4. The sample stored in the powder state showed an increase in molecular weight and an increase in acid value, confirming that the resin had deteriorated. On the other hand, the sample stored in the solution state showed almost no change in both molecular weight and acid amount.

Claims (10)

Photoresist copolymer comprising a repeating unit having a lactone structure and a repeating unit having an acidic group (however, radical polymerization is carried out using a monomer solution containing a polymerization inhibitor of 20 mol ppm or more based on the monomer). a storage method of the resulting excluding was something), water content, characterized in that stored in the following solutions 500ppm of the copolymer by a hydroxy group-free solvent, save the photo resist copolymer Method.   The hydroxy group-free solvent is at least one solvent selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and hexane. How to save.   The storage method according to claim 1 or 2, wherein the acidic group is a substituent having a pKa of 10 or less.   The storage method according to any one of claims 1 to 3, wherein the acidic group is a substituent having a pKa of 6 or less or a phenolic hydroxy group. The storage method according to any one of claims 1 to 4, wherein the acidic group is at least one selected from the group consisting of a carboxyl group, a phenol group, a naphthol group, a thiol group, and a sulfo group. The repeating unit having the lactone structure has the formula (A):

[Wherein, R ₁₀ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms which may be substituted by fluorine, and R ₁₁ represents the formula (a)

_(Wherein, R 12 _{to R 19} is any _one, it represents a single bond having a binding site for the _{R 11,} the remainder of _R 12 _{to R 19} is a hydrogen atom or a hydrocarbon of 1 to 4 carbon atoms Each of which represents a hydrogen group or an alkoxy group, or any one of them has a bonding site as R ₁₁ and is bonded to any one or two of other R _{12 to} R ₁₉ and has 5 to 15 carbon atoms Represents a hydrocarbon group having 3 to 14 carbon atoms which may contain an oxygen atom or a sulfur atom to form an alicyclic ring, and the remaining R _{12 to} R ₁₉ are either one or two of the above-mentioned 5 to 15 carbon atoms A single bond for forming an alicyclic ring, and the remainder represents a hydrogen atom, a hydrocarbon group or an alkoxy group having 1 to 4 carbon atoms, and m represents an integer of 0 or 1. The lactone structure-containing group represented is represented. ]
The preservation | save method as described in any one of Claims 1-5 which has a structure represented by these.   The storage method according to claim 1, further comprising keeping the copolymer solution in a sealed state in the storage method.   The storage method according to claim 1, further comprising keeping the copolymer solution at 20 ° C. or lower in the storage method.   The storage method according to any one of claims 1 to 8, further comprising keeping the copolymer solution in a light-shielding state in the storage method.   The manufacturing method of the composition for photoresists characterized by using the copolymer preserve | saved by the preservation | save method as described in any one of Claims 1-9.