JP4646582B2 - Method for producing a copolymer for photoresist - Google Patents

Description

  The present invention relates to a copolymer for photoresist and a method for producing the same, and more specifically, a copolymer for photoresist useful as a photosensitive resin such as photoresist or a precursor for obtaining the photosensitive resin, and a method for producing the same. About.

  A copolymer obtained by polymerizing a styrene monomer and / or an acrylic monomer is used as a photosensitive resin such as a resist or a precursor for obtaining this photosensitive resin. In order to improve resist performance such as heat resistance, sensitivity, and resolution of these copolymers, conventionally, an alkali solution (development is performed by adjusting the composition ratio and molecular weight of the copolymer or adjusting the acid value. Attempts have been made to improve the resolution by reducing the dissolution residue in the liquid) or modifying the copolymer with a specific compound.

  However, sufficiently satisfactory resist performance is not always obtained even with the copolymer obtained by the above method. In addition, when adjusting the copolymer composition ratio or improving the heat resistance, sensitivity, and resolution of the copolymer by a method of modifying the copolymer, the film thickness of the resist or the line width of the resist may be reduced. There are problems, such as occurring. Further, when the molecular weight of the copolymer is lowered, the solubility in an alkaline solution is improved, but there is a problem that the dry etching resistance of the polymer is lowered.

  Japanese Patent Application Laid-Open No. 2001-2717 discloses a method for producing a resist resin whose solubility in an alkali is changed by the action of an acid, using a polymerization initiator having a specific structure. However, the polymer described in this publication is not sufficient in terms of sensitivity and the like.

JP 2001-2717 A

An object of the present invention is to provide a copolymer for photoresist that is excellent in resist performance such as heat resistance, sensitivity, and resolution, and that can form a fine pattern clearly and accurately, and a method for producing the same.
Another object of the present invention is to provide a copolymer for photoresist and a method for producing the same, which have no resist film thickness reduction or line width reduction, high resistance to dry etching, and excellent resist performance such as heat resistance, sensitivity and resolution. There is to do.

  As a result of intensive studies to achieve the above object, the present inventors have found that when two or more specific monomers are copolymerized using a polymerization initiator having a specific structure, resist performance such as heat resistance, sensitivity, and resolution is improved. The inventors have found that a significantly excellent copolymer for photoresist can be obtained and completed the present invention.

（式中、Ｒ¹は水素原子又は炭素数１〜６のアルキル基を示し、Ｒ²は炭素数１〜１２の第１級若しくは第２級アルキル基、炭素数２〜１２のアルケニル基、又はオキシラン環若しくはオキセタン環含有基を示す）
で表される不飽和カルボン酸エステル、及び（iii）Ｎ−置換マレイミドの３種の単量体群より選択された少なくとも２種の単量体群に含まれる２以上のモノマーと、（Ｂ）アルカリ可溶性基含有モノマーとを、下記式（２）

（式中、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶、Ｒ⁷、Ｒ⁸は、同一又は異なって、水素原子、炭素数１〜１２のアルキル基、炭素数６〜１５のアリール基、又は炭素数７〜１６のアラルキル基を示す）
で表される重合開始剤を用いて共重合させることを特徴とするフォトレジスト用共重合体の製造法を提供する。 That is, the present invention provides (A) (i) styrene optionally substituted with an alkyl group, (ii) the following formula (1)

(Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² represents a primary or secondary alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or Indicates an oxirane ring or oxetane ring-containing group)
And (iii) two or more monomers included in at least two monomer groups selected from three monomer groups of N-substituted maleimides, and (B) An alkali-soluble group-containing monomer is represented by the following formula (2)

(In the formula, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and are a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 15 carbon atoms, or Represents an aralkyl group having 7 to 16 carbon atoms)
The production method of the copolymer for photoresists characterized by making it copolymerize using the polymerization initiator represented by these.

  In one embodiment of this production method, at least styrene (i) or N-substituted maleimide (iii) optionally substituted with an alkyl group, and an unsaturated carboxylic acid ester (ii) represented by formula (1) ) And an alkali-soluble group-containing monomer (B).

（式中、Ａ¹、Ａ²、Ａ³は、それぞれ、単結合又は連結基を示し、Ｒ⁹、Ｒ¹⁰は、それぞれ、水素原子又は炭素数１〜６のアルキル基を示す。式（ａ）中のオキセタン環、式（ｂ）中のシクロヘキサン環、式（ｃ）中のオキシラン環は置換基を有していてもよい） As oxirane ring or an oxetane ring-containing group in R ² of formula (1), for example, the following formula (a), include (b) or (c).

(In the formula, A ¹ , A ² and A ³ each represent a single bond or a linking group, and R ⁹ and R ¹⁰ each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The oxetane ring in the formula (b), the cyclohexane ring in the formula (b), and the oxirane ring in the formula (c) may have a substituent.

  As the alkali-soluble group-containing monomer (B), for example, an unsaturated carboxylic acid or an acid anhydride thereof can be used.

  As the polymerization initiator represented by the formula (2), for example, dimethyl-2,2′-azobis (2-methylpropionate) is used.

  The usage-amount of the polymerization initiator represented by Formula (2) is about 1 to 10 weight% with respect to the total amount of a monomer and a polymerization initiator, for example.

  The present invention also provides a copolymer for photoresist obtained by the above production method. The number average molecular weight of this copolymer is, for example, about 3000 to 30000.

  According to the production method of the present invention, it is possible to obtain a copolymer for photoresist that is excellent in resist performance such as heat resistance, sensitivity, and resolution, and that can form a fine pattern clearly and accurately. When the photoresist copolymer thus obtained is used, resist film loss and line width reduction can be suppressed, and dry etching resistance can be improved.

  In the production method of the present invention, (A) (i) styrene optionally substituted with an alkyl group, (ii) an unsaturated carboxylic acid ester represented by the above formula (1), and (iii) ) Two or more monomers selected from three monomer groups selected from the three monomer groups of N-substituted maleimide in total, and (B) an alkali-soluble group-containing monomer.

  Examples of the “alkyl group” in the styrene (i) optionally substituted with the alkyl group include about 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, hexyl group and the like. Of the alkyl group. Among these, an alkyl group having 1 to 4 carbon atoms such as a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable. The alkyl group may be bonded to either the vinyl group of styrene or the benzene ring.

  Typical examples of styrene (i) which may be substituted with an alkyl group include styrene, α-methylstyrene, vinyltoluene (o-vinyltoluene, m-vinyltoluene, p-vinyltoluene) and the like. Styrene (i) optionally substituted with an alkyl group can be used alone or in combination of two or more. The monomer (i) has a function of imparting a hardness necessary as a resist to the film.

In the unsaturated carboxylic acid ester (ii) represented by the formula (1), in the formula (1), the alkyl group having 1 to 6 carbon atoms in R ¹ and preferred examples thereof are the same as described above. Examples of the primary or secondary alkyl group having 1 to 12 carbon atoms in R ² include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, hexyl, octyl, decyl, dodecyl groups and the like. It is done. Examples of the alkenyl group having 2 to 12 carbon atoms include primary or secondary alkenyl groups such as allyl, 3-butenyl, and 5-hexenyl groups.

Further, the oxirane ring or oxetane ring-containing group in R ² is not particularly limited, and for example, (1) an oxirane ring or oxetane ring is directly connected to an oxygen atom constituting the ester bond (an oxygen atom adjacent to R ² ). Or a group to which an alicyclic ring fused with an oxirane ring or an oxetane ring is bonded, or (2) an oxirane ring, an oxetane ring, or an oxirane ring or an oxetane ring having two carbon atoms A group in which an alicyclic ring condensed by sharing an atom is bonded; (3) an oxirane ring, an oxetane ring, or an oxirane ring or an oxetane ring has two carbon atoms between carbon atoms constituting a hydrocarbon group. Examples include a group in which a shared and condensed alicyclic ring is inserted. Examples of the alicyclic ring in which the oxirane ring is condensed by sharing two carbon atoms include an epoxycyclopentane ring, an epoxycyclohexane ring, and an epoxycyclooctane ring.

Representative examples of the oxirane ring or oxetane ring-containing group include groups represented by the formula (a), (b), or (c). In the formula, A ¹ , A ² and A ³ each represent a single bond or a linking group, and R ⁹ and R ¹⁰ each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The oxetane ring in formula (a), the cyclohexane ring in formula (b), and the oxirane ring in formula (c) may have a substituent.

Examples of the linking group in A ¹ , A ² and A ³ include a divalent hydrocarbon group, an oxygen atom (ether bond), a sulfur atom (thioether bond), an ester bond, an amide bond, and a carbonyl group. Examples include a bonded group. Examples of the divalent hydrocarbon group include alkylene groups such as methylene, ethylene, propylene, and trimethylene groups (for example, linear or branched alkylene groups having about 1 to 6 carbon atoms); vinylene, propenylene groups, and the like Alkenylene group (for example, a linear or branched alkylene group having about 2 to 6 carbon atoms); 1,2-cyclopentylene, 1,3-cyclopentylene, 1,2-cyclohexylene, Cycloalkylene groups such as 1,3-cyclohexylene and 1,4-cyclohexylene groups (eg, about 3 to 8 membered cycloalkylene groups); Cycloalkylidene groups such as cyclopentylidene and cyclohexylidene groups (eg 3 ˜8-membered cycloalkylidene group and the like); arylene groups such as 1,4-phenylene group and the like. Examples of the group in which two or more divalent hydrocarbon groups are bonded include, for example, a group in which two or more hydrocarbon groups are bonded in two or more, a plurality of (for example, two) hydrocarbon groups are oxygen atoms, sulfur atoms, and esters. Examples thereof include a bond, an amide bond, or a group bonded through a carbonyl group.

Preferred linking groups, divalent, such as (C _1-4 alkylene group such as especially methylene) alkylene hydrocarbon group, divalent, such as (C _1-4 alkylene group such as especially methylene) alkylene group A group in which a plurality (for example, 2) of hydrocarbon groups are bonded via an oxygen atom or a sulfur atom (—C _1-4 alkylene-O—C _1-4 alkylene-, —C _1-4 alkylene-S—); C _1-4 alkylene- and the like.

The alkyl group having 1 to 6 carbon atoms in R ⁹ and R ¹⁰ is the same as described above. The substituent which may be bonded to the oxetane ring in the formula (a), the cyclohexane ring in the formula (b), or the oxirane ring in the formula (c) is any substituent that does not impair the resist performance. well, for example, methyl, ethyl, propyl, isopropyl, (such as C _1-6 alkyl group) alkyl group such as butyl group, methoxy, ethoxy, alkoxy groups such as propyl group (C _1-6 alkoxy group), etc. Can be mentioned.

  Examples of the group represented by the formula (a) include oxetanyl group, 3-methyl-3-oxetanyl group, 3-ethyl-3-oxetanyl group, (3-methyl-3-oxetanyl) methyl group, (3-ethyl -3-Oxetanyl) methyl group, 2- (3-methyl-3-oxetanyl) ethyl group, 2- (3-ethyl-3-oxetanyl) ethyl group, 2-[(3-methyl-3-oxetanyl) methyloxy ] Ethyl group, 2-[(3-ethyl-3-oxetanyl) methyloxy] ethyl group, 3-[(3-methyl-3-oxetanyl) methyloxy] propyl group, 3-[(3-ethyl-3- And oxetanyl) methyloxy] propyl group.

  Examples of the group represented by the formula (b) include 3,4-epoxycyclohexyl group, 3,4-epoxycyclohexylmethyl group, 2- (3,4-epoxycyclohexyl) ethyl group, 2- [3,4- Examples include an epoxycyclohexylmethyloxy] ethyl group, a 3- [3,4-epoxycyclohexylmethyloxy] propyl group, and a corresponding group in which 1 to 3 methyl groups are bonded to the cyclohexane ring of these groups.

  Examples of the group represented by the formula (c) include oxiranyl group, glycidyl group, 2-methylglycidyl group, 2-ethylglycidyl group, 2-oxiranylethyl group, 2-glycidyloxyethyl group, and 3-glycidyloxy. A propyl group, a glycidyloxyphenyl group, etc. are mentioned.

Of the unsaturated carboxylic acid ester (ii) represented by the formula (1), R ² is a primary or secondary alkyl group having 1 to 12 carbon atoms or an alkenyl group having 2 to 12 carbon atoms. Representative examples of (ii-1) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, Examples include isobutyl (meth) acrylate and allyl (meth) acrylate. The monomer (ii-1) has a function of imparting a hardness necessary as a resist to the film, and also has a function of smoothly progressing the copolymerization when the styrene monomer is copolymerized.

Of the unsaturated carboxylic acid ester (ii) represented by the formula (1), a representative example of the compound (ii-2) in which R ² is an oxirane ring or oxetane ring-containing group includes, for example, 3-methyl -3-Oxetanyl (meth) acrylate, 3-ethyl-3-oxetanyl (meth) acrylate, (3-methyl-3-oxetanyl) methyl (meth) acrylate, (3-ethyl-3-oxetanyl) methyl (meth) acrylate 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, 2-methylglycidyl (meth) acrylate, 2-ethylglycidyl (meth) acrylate, and the like. The monomer (ii-2) is cured by crosslinking with a crosslinking agent or by reaction with an alkali-soluble group (for example, carboxyl group, phenolic hydroxyl group, etc.) in the polymer molecule, and is required as a resist for the film. Has a function of changing the polymer to alkali-insoluble. Therefore, the polymer containing the monomer structural unit is particularly useful as a negative resist polymer. The crosslinking agent is not particularly limited as long as the oxirane ring or oxetane ring is opened to cause a crosslinking reaction. For example, a crosslinking agent (for example, a hydroxyl group-containing compound, a carboxyl group, or an acid) that is usually used in the resist field. An anhydride group-containing compound, polyamine, etc.) can be used.

  The unsaturated carboxylic acid ester (ii) represented by the formula (I) can be used alone or in combination of two or more. For example, one or more of the monomers (ii-1) and one or more of the monomers (ii-2) can be used in combination.

  The N-substituted maleimide (iii) is not particularly limited, and examples thereof include N-cycloalkylmaleimide such as N-cyclopentylmaleimide, N-cyclohexylmaleimide, N-cyclooctylmaleimide; N-adamantylmaleimide, N-norbornol. N-bridged carbocyclic group-substituted maleimides such as nilmaleimide; N-alkylmaleimides such as N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide; N-arylmaleimides such as N-phenylmaleimide; N-benzyl N-aralkylmaleimide such as maleimide may be used. Among these, N-cycloalkylmaleimide such as N-cyclohexylmaleimide, N-bridged carbocyclic group-substituted maleimide, and the like are preferable. N-substituted maleimide (iii) can be used individually or in combination of 2 or more types. The monomer (iii) has a function of imparting a hardness necessary as a resist to the film and a function of facilitating the copolymerization reaction.

  The monomer component (A) includes two or more (total) monomers contained in at least two monomer groups selected from the three monomer groups (i) to (iii). Among them, (A) includes (1) a combination of styrene (i) optionally substituted with an alkyl group and unsaturated carboxylic acid ester (ii) represented by formula (1), (2) A combination of (ii) and N-substituted maleimide (iii), and a combination of (3) (i), (ii) and (iii) are preferred.

In the case of (1), the ratio of (i) and (ii) is, for example, the former / the latter (weight ratio) = 1/99 to 99/1, preferably 3/97 to 98/2. In the case of (1), as unsaturated carboxylic acid ester (ii) represented by formula (1), in particular, R ² is an alkyl group having 1 to 12 carbon atoms or an alkenyl group having 2 to 12 carbon atoms. It is preferable to use the compound (ii-1). By using (ii-1), the copolymerization reaction of the monomer (i) and the alkali-soluble group-containing monomer (B) or the like can proceed more smoothly. In this case, the ratio of (i) and (ii-1) is, for example, the former / the latter (weight ratio) = 70/30 to 99/1, preferably 80/20 to 98/2, more preferably 90/10. ~ 97/3. If this ratio is too large, the copolymerization reaction will not proceed smoothly, and if it is too small, the hardness of the film will tend to be insufficient.

In the case of (2), the ratio of (ii) and (iii) is, for example, the former / the latter (weight ratio) = 1/99 to 99/1, preferably 3/97 to 98/2. In the case of (2), in particular, as unsaturated carboxylic acid ester (ii) represented by formula (1), compound (ii-2) in which R ² is an oxirane ring or oxetane ring-containing group is used. Is preferred. In this case, the ratio of (ii-2) and (iii) is, for example, the former / the latter (weight ratio) = 20/80 to 99/1, preferably 40/60 to 98/2. If this ratio is too large, the hardness of the film will be insufficient or the copolymerization reaction will not proceed smoothly. Conversely, if it is too small, the crosslinking reaction will be insufficient, and it will be used for negative resists. In some cases, not only the unexposed portion but also the polymer at the exposed portion is dissolved in the alkali developer, and it is difficult to form a fine pattern clearly and accurately.

  The ratio of each monomer component in the case (3) can be set according to the above (1) and (2).

  The alkali-soluble group-containing monomer (B) has a function of imparting alkali solubility to the polymer. As a result, the polymer is dissolved in an alkaline solution (developer) at the time of development. Therefore, the polymer containing the monomer structural unit is useful as a photoresist polymer. Further, the alkali-soluble group-containing monomer (B) is obtained by crosslinking using a crosslinking agent, or an oxirane ring or oxetane ring-containing group in the polymer molecule [for example, a group derived from the monomer (ii-2), etc. The polymer containing the monomer structural unit is extremely useful as a negative resist polymer. Useful. The crosslinking agent is not particularly limited as long as it causes a crosslinking reaction with an alkali-soluble group (for example, carboxyl group, phenolic hydroxyl group, etc.), and is generally used in the resist field (for example, melamine resin, urea). Resin, polyisocyanate, epoxy resin, etc.) can be used. In the case of a negative resist, the resin in the exposed area can be changed to be insoluble in alkali by further increasing the molecular weight by further polymerization by light irradiation.

  The alkali-soluble group in the alkali-soluble group-containing monomer (B) may be any group usually used in the resist field, and examples thereof include a carboxyl group and a phenolic hydroxyl group. Representative examples of the alkali-soluble group-containing monomer (B) include, but are not limited to, unsaturated carboxylic acids or acid anhydrides thereof, hydroxystyrene or derivatives thereof. Among these, unsaturated carboxylic acid or its acid anhydride is particularly preferable.

  Examples of unsaturated carboxylic acids or acid anhydrides thereof include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and acid anhydrides thereof (maleic anhydride, An itaconic anhydride, etc.). Among these, acrylic acid and methacrylic acid are particularly preferable. The alkali-soluble group-containing monomer (B) can be used alone or in combination of two or more.

  The ratio of the monomer components (A) and (B) varies depending on the type of monomer used and the type of resist (negative type or positive type), but usually the former / the latter (weight ratio) = 40/60 to It is about 98/2, preferably 50/50 to 95/5, and more preferably about 60/40 to 92/8. If this ratio is too large, it will be difficult to dissolve in an alkaline developer, and if it is too small, the hardness of the film will tend to be insufficient.

  In the production method of the present invention, various functions required as a resist [alkaline soluble function, etching resistance imparting function, transparency imparting function, adhesion function to a substrate, solubility function for a resist solvent, part of the structure is removed by an acid. In order to impart an acid-eliminating function (for positive resists, etc.) that becomes alkali-soluble when released, and to facilitate the copolymerization reaction, monomer components other than the above are copolymerized as necessary. You may attach. However, the sum of the monomer components (A) and (B) is usually 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably based on the total monomer components. Is 95% by weight or more, and the copolymer may be substantially composed only of (A) and (B).

  In the present invention, the compound represented by the formula (2) is used as a polymerization initiator. When the compound represented by the formula (2) was used as the polymerization initiator, a nitrile group-containing polymerization initiator such as 2,2′-azobisisobutyronitrile (AIBN) or a peroxide polymerization initiator was used. Compared to the case, a polymer having high light transmittance, excellent heat resistance, and high solubility in an alkaline solution can be obtained. Therefore, when this polymer is used for a photoresist, a desired pattern can be obtained with high sensitivity and resolution. In addition, it is possible to suppress a reduction in resist film thickness, a reduction in resist line width, and a decrease in dry etching resistance.

In formula (2), R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 15 carbon atoms, or carbon. The aralkyl group of several 7-16 is shown.

  Examples of the alkyl group having 1 to 12 carbon atoms include linear or branched groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, octyl, decyl, and dodecyl groups. A chain alkyl group is exemplified. Among these, a C1-C6 alkyl group, especially a C1-C4 alkyl group are preferable.

  Examples of the aryl group having 6 to 15 carbon atoms include a phenyl group and a naphthyl group. Examples of the aralkyl group having 7 to 16 carbon atoms include a benzyl group, a 2-phenylethyl group, and a 3-phenylpropyl group.

  Representative examples of the compound represented by the formula (2) include dimethyl-2,2′-azobis (2-methylpropionate), diethyl-2,2′-azobis (2-methylpropionate), And dibutyl-2,2'-azobis (2-methylpropionate). Of these, dimethyl-2,2'-azobis (2-methylpropionate) is particularly preferable.

  The amount of the polymerization initiator represented by the formula (2) can be appropriately selected within a range that does not impair smooth copolymerization. Usually, the total amount of monomers (total monomer components) and polymerization initiator is It is about 1-10 weight%, Preferably it is about 2-8 weight%.

  The copolymerization can be performed by a conventional method used for producing a styrene polymer or an acrylic polymer, such as solution polymerization, bulk polymerization, suspension polymerization, bulk-suspension polymerization, and emulsion polymerization. Among these, solution polymerization is preferable. The monomer and the polymerization initiator may be supplied all at once to the reaction system, or a part or all of them may be dropped into the reaction system. For example, a method in which a solution in which a polymerization initiator is dissolved in a polymerization solvent is dropped into a mixed solution of a monomer and a polymerization solvent kept at a constant temperature, or the monomer and the polymerization initiator are dissolved in the polymerization solvent in advance. A method in which the solution is dropped into a polymerization solvent maintained at a constant temperature for polymerization (drop polymerization method) can be employed.

  The polymerization solvent can be appropriately selected according to the monomer composition and the like. Examples of the polymerization solvent include ethers (chain ethers such as diethyl ether, 3-methoxy-1-butanol, glycol ethers such as propylene glycol monomethyl ether and diethylene glycol ethyl methyl ether, and cyclic ethers such as tetrahydrofuran and dioxane), esters. (Methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, 3-methoxybutyl acetate, ethyl-3-ethoxypropionate, glycol ether esters such as propylene glycol monomethyl ether acetate, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl) Ketone, cyclohexanone, etc.), amide (N, N-dimethylacetamide, N, N-dimethylformamide, etc.), sulfoxide (dimethylsulfoxide) Etc.), alcohol (methanol, ethanol, propanol, etc.), hydrocarbon (aromatic hydrocarbons such as benzene, toluene, xylene, aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, etc.), and mixtures thereof A solvent etc. are mentioned. The polymerization temperature can be appropriately selected within a range of about 30 to 150 ° C., for example.

  According to the above method, (A) (i) styrene optionally substituted with an alkyl group, (ii) unsaturated carboxylic acid ester represented by the above formula (1), and (iii) N-substituted maleimide A structural unit (repeating unit) corresponding to two or more monomers included in at least two monomer groups selected from the monomer group of (B), and a structural unit (repeating unit) corresponding to (B) the alkali-soluble group-containing monomer. Unit). The number average molecular weight of the copolymer is, for example, 3000 to 30000, preferably 3500 to 25000, and more preferably about 4000 to 20000.

  The polymerization solution obtained by the above method is adjusted to a solid content concentration or subjected to a filtration treatment as necessary, and then to this, a photoacid generator, a crosslinking agent (in the case of a negative resist), a resin, a coloring By adding an appropriate additive such as an agent, it can be used as a resin composition for a photoresist. Moreover, the polymer produced | generated by superposition | polymerization can also be utilized as a resin composition for photoresists by refine | purifying by precipitation or reprecipitation etc., and melt | dissolving this refined polymer in the solvent for resists with the said appropriate additive. . As the additive such as the photoacid generator and the crosslinking agent and the solvent for the resist, those generally used in the resist field can be used depending on the monomer composition and the like.

  The solvent used for polymer precipitation or reprecipitation may be either an organic solvent or water, or a mixed solvent thereof. Examples of organic solvents include hydrocarbons (aliphatic hydrocarbons such as pentane, hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene), halogenated Hydrocarbons (halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene), nitro compounds (nitromethane, nitroethane, etc.), nitriles (acetonitrile, benzonitrile) Etc.), ethers (chain ethers such as diethyl ether, diisopropyl ether and dimethoxyethane; cyclic ethers such as tetrahydrofuran and dioxane), ketones (acetone, methyl ethyl ketone, diisobutyl ketone, etc.), Tell (ethyl acetate, butyl acetate etc.), carbonate (dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate etc.), alcohol (methanol, ethanol, propanol, isopropyl alcohol, butanol etc.), carboxylic acid (acetic acid etc.), these Examples thereof include a mixed solvent containing a solvent.

Thus obtained copolymer may be, for example, g-ray exposure, i-rays, excimer laser (e.g., XeCl, KrF, KrCl, ArF , ArCl, F 2, Kr 2, KrAr, Ar 2 , etc.) photo with like It is suitably used as a resist polymer, particularly as a negative photoresist polymer.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The number average molecular weight of the copolymer was measured using a GPC (gel permeation chromatography) apparatus (trade name “K2479”) manufactured by Shimadzu Corporation. The analysis conditions are as follows.
Column: SHIMAZU Shin-pack GPC-80M
Eluent: THF (tetrahydrofuran) 1 ml / min
Temperature (oven): 40 ° C
Detector: RI

Example 1
A separable flask was charged with 210 g of 3-methoxybutyl acetate, 230 g of styrene monomer, 10 g of methyl methacrylate, and 65 g of methacrylic acid, and the temperature was raised to 80 ° C. after purging with nitrogen. When the temperature of the contents reached 80 ° C., a solution prepared by dissolving 25 g of dimethyl-2,2′-azobis (2-methylpropionate) as a polymerization initiator in 160 g of 3-methoxybutyl acetate was taken over about 7 hours. And dripped. After completion of dropping of the polymerization initiator solution, the reaction was continued for about 1 hour, and then the reaction vessel was cooled to complete the reaction. To this solution, 300 g of 3-methoxybutyl acetate was added, the solid content concentration was adjusted, and about 1 kg of a 3-methoxybutyl acetate solution of a styrene / methyl methacrylate / methacrylic acid copolymer was obtained. The resulting copolymer solution had a solid content concentration of 29.5% by weight, an acid value of 42.4 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 60 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 8,000.

Example 2
In a separable flask, 210 g of a mixed solvent of diethylene glycol ethyl methyl ether and ethyl-3-ethoxypropionate [former / latter (weight ratio) = 340/345], 120 g of N-cyclohexylmaleimide, 3-ethyl-3-oxetanylmethyl After adding 140 g of methacrylate and 40 g of methacrylic acid and replacing with nitrogen, the temperature was raised to 80 ° C. When the temperature of the contents reaches 80 ° C., a solution obtained by dissolving 15 g of dimethyl-2,2′-azobis (2-methylpropionate) as a polymerization initiator in 160 g of the mixed solvent is dropped over about 7 hours. did. After completion of dropping of the polymerization initiator solution, the reaction was continued for about 1 hour, and then the reaction vessel was cooled to complete the reaction. To this solution, 315 g of the mixed solvent was added to adjust the solid concentration, and about 1 kg of the mixed solvent solution of N-cyclohexylmaleimide / 3-ethyl-3-oxetanylmethyl methacrylate / methacrylic acid copolymer was obtained. The obtained copolymer solution had a solid content concentration of 28.9% by weight, an acid value of 26.5 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 85 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 4400.

Example 3
In a separable flask, 210 g of a mixed solvent of 3-methoxybutyl acetate and 3-methoxy-1-butanol [former / latter (weight ratio) = 330/340], 40 g of N-cyclohexylmaleimide, 180 g of methyl glycidyl methacrylate, and methacrylic acid After putting 80 g and replacing with nitrogen, the temperature was raised to 80 ° C. When the temperature of the contents reaches 80 ° C., a solution prepared by dissolving 30 g of dimethyl-2,2′-azobis (2-methylpropionate) as a polymerization initiator in 160 g of the mixed solvent is dropped over about 7 hours. did. After completion of dropping of the polymerization initiator solution, the reaction was continued for about 1 hour, and then the reaction vessel was cooled to complete the reaction. To this solution, 300 g of the mixed solvent was added to adjust the solid content concentration, and about 1 kg of the mixed solvent solution of N-cyclohexylmaleimide / methylglycidyl methacrylate / methacrylic acid copolymer was obtained. The obtained copolymer solution had a solid content concentration of 29.8% by weight, an acid value of 52.1 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 110 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 8,900.

Example 4
In a separable flask, 210 g of a mixed solvent of 3-methoxybutyl acetate and 3-methoxy-1-butanol [former / latter (weight ratio) = 330/340], 40 g of N-cyclohexylmaleimide, 3,4-epoxycyclohexylmethyl methacrylate 180 g and 80 g of methacrylic acid were added, and after nitrogen substitution, the temperature was raised to 80 ° C. When the temperature of the contents reaches 80 ° C., a solution prepared by dissolving 30 g of dimethyl-2,2′-azobis (2-methylpropionate) as a polymerization initiator in 160 g of the mixed solvent is dropped over about 7 hours. did. After completion of dropping of the polymerization initiator solution, the reaction was continued for about 1 hour, and then the reaction vessel was cooled to complete the reaction. To this solution, 300 g of the mixed solvent was added to adjust the solid content concentration, and about 1 kg of the mixed solvent solution of N-cyclohexylmaleimide / 3,4-epoxycyclohexylmethyl methacrylate / methacrylic acid copolymer was obtained. The obtained copolymer solution had a solid content concentration of 29.5% by weight, an acid value of 52.1 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 130 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 9,600.

Comparative Example 1
The same procedure as in Example 1 except that 25 g of dimethyl-2,2'-azobis (2,4-dimethylvaleronitrile) was used instead of dimethyl-2,2'-azobis (2-methylpropionate). And about 1 kg of a styrene / methyl methacrylate / methacrylic acid copolymer solution was obtained. The resulting copolymer solution had a solid content concentration of 29.5% by weight, an acid value of 42.4 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 65 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 8,000.

Comparative Example 2
N-cyclohexylmaleimide / 3-ethyl was prepared in the same manner as in Example 2 except that 15 g of azobisisobutyronitrile was used instead of dimethyl-2,2′-azobis (2-methylpropionate). About 1 kg of a solution of -3-oxetanylmethyl methacrylate / methacrylic acid copolymer was obtained. The obtained copolymer solution had a solid content concentration of 29.7% by weight, an acid value of 26.1 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 83 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 4,500.

Comparative Example 3
The same procedure as in Example 3 except that 30 g of dimethyl-2,2'-azobis (2,4-dimethylvaleronitrile) was used instead of dimethyl-2,2'-azobis (2-methylpropionate). And about 1 kg of a solution of N-cyclohexylmaleimide / methylglycidyl methacrylate / methacrylic acid copolymer was obtained. The obtained copolymer solution had a solid content concentration of 28.9% by weight, an acid value of 52.1 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 103 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 9000.

Comparative Example 4
N-cyclohexylmaleimide / 3, 4 was carried out in the same manner as in Example 4 except that 30 g of azobisisobutyronitrile was used instead of dimethyl-2,2′-azobis (2-methylpropionate). -About 1 kg of an epoxy cyclohexyl methyl methacrylate / methacrylic acid copolymer solution was obtained. The obtained copolymer solution had a solid content concentration of 29.1% by weight, an acid value of 52.1 mg-KOH / g, and a viscosity (23 ° C.) measured by a B-type viscometer of 140 mPa · s. Moreover, the number average molecular weight of polystyrene conversion by GPC of the copolymer was 9,300.

Evaluation Test The following evaluation tests were performed using the copolymer solutions obtained in the examples and comparative examples. The results are shown in Table 1.

(1) Developability Each copolymer solution obtained in Examples and Comparative Examples was diluted to a solid content concentration of 3.6% by weight. This solution was applied to a substrate (SUS304, 0.5 × 80 × 80 mm, puffed, single-sided SPV, Japanese test panel, standard test plate) using a bar coater, and dried in an oven at 120 ° C. for 2 hours. The sample was immersed in an alkaline developer (tetramethylammonium hydroxide 2.35 wt% aqueous solution) stretched to a height of about 1 cm in a stainless steel bat, and the time until the resin layer was completely dissolved and removed was measured. .

(2) Light transmittance Each copolymer solution (solid content of about 30% by weight) obtained in Examples and Comparative Examples was put into a 10 × 10 mm quartz glass container, and UV-spectrometer (manufactured by Hitachi, Ltd., product) The light transmittance at a wavelength of 365 nm was measured using the name “U-3300”). In addition, what put the solvent of the same composition as the solvent of each copolymer solution in the quartz glass container of the same shape was used as a base. The light transmittance is calculated based on the base transmittance. The light transmittance needs to be 95% or more, and if it is less than 95%, the sensitivity is poor.

(3) Heat resistance 20-40 mg of each copolymer solution obtained in Examples and Comparative Examples was placed in an aluminum pan for measuring TG / DTA, and this was placed in an oven at a temperature of 120 ° C. After drying for a period of time and measuring the weight to calculate the weight of the sample, the sample was subjected to a TG / DTA tester (thermogravimetry / differential thermal analysis tester; manufactured by Seiko Denshi Kogyo, trade name “TG / DTA6300”). Aluminum oxide was used as a reference sample. The temperature (melting point) at the first inflection point of the TG curve was read and used as an index of the heat resistance of the resin.

As is apparent from the table, the copolymers obtained in the examples are remarkably superior in terms of developability, light transmittance and heat resistance as compared with the copolymers obtained in the comparative examples.

Claims (8)

(A) (i) Styrene optionally substituted with an alkyl group, (ii) The following formula (1)

(Wherein R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² represents a primary or secondary alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or Indicates an oxirane ring or oxetane ring-containing group)
And (iii) two or more monomers included in at least two monomer groups selected from three monomer groups of N-substituted maleimides, and (B) An alkali-soluble group-containing monomer is represented by the following formula (2)

(In the formula, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different and are a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 15 carbon atoms, or Represents an aralkyl group having 7 to 16 carbon atoms)
A method for producing a copolymer for photoresist, which comprises copolymerization using a polymerization initiator represented by the formula:   At least styrene (i) or N-substituted maleimide (iii) optionally substituted with an alkyl group, unsaturated carboxylic acid ester (ii) represented by formula (1), and alkali-soluble group-containing monomer (B A method for producing a photoresist copolymer according to claim 1. The oxirane ring or oxetane ring-containing group in R ² of formula (1) is represented by the following formulas (a), (b), (c)

(In the formula, A ¹ , A ² and A ³ each represent a single bond or a linking group, and R ⁹ and R ¹⁰ each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The oxetane ring in the formula (b), the cyclohexane ring in the formula (b), and the oxirane ring in the formula (c) may have a substituent.
The method for producing a copolymer for a photoresist according to claim 1 or 2, wherein the group is any one of the groups.   The method for producing a photoresist copolymer according to any one of claims 1 to 3, wherein the alkali-soluble group-containing monomer (B) is an unsaturated carboxylic acid or an acid anhydride thereof.   The copolymer for photoresists according to any one of claims 1 to 4, wherein the polymerization initiator represented by formula (2) is dimethyl-2,2'-azobis (2-methylpropionate). Manufacturing method.   The amount of the polymerization initiator represented by the formula (2) is 1 to 10% by weight based on the total amount of the monomer and the polymerization initiator, and the photoresist co-polymer according to any one of claims 1 to 5. Production method of polymer.   The copolymer for photoresists obtained by the manufacturing method in any one of Claims 1-6. The number average molecular weight is 3000 to 30000, The copolymer for photoresists of Claim 7.