JP5459026B2 - Radiation sensitive resin composition - Google Patents

Description

  The present invention relates to a radiation-sensitive resin composition, and more particularly to a radiation-sensitive resin composition used in a semiconductor manufacturing process such as an IC, a circuit board such as a liquid crystal or a thermal head, and other photolithography processes.

  The chemically amplified radiation-sensitive resin composition generates an acid in an exposed area by irradiation with far ultraviolet light or the like typified by a KrF excimer laser or an ArF excimer laser, and reacts with the acid as a catalyst to react with the exposed area. It is a composition that changes the dissolution rate of the unexposed portion with respect to the developer to form a resist pattern on the substrate.

  When more precise line width control is performed, for example, when the device design dimension is sub-half micron or less, the chemically amplified resist not only has excellent resolution performance but also resist pattern line. It has become important that LWR (Line Width Roughness), which is an index of variation in width, is small and the pattern shape is rectangular. In order to control such a fine shape, a technique of adding a basic compound as an acid diffusion control agent for adjusting the diffusion rate of the generated acid is disclosed (for example, see Patent Documents 1 and 2). .

JP-B-2-27660 JP 2009-53688 A

  The technique of adding a basic compound as an acid diffusion control agent that loses acid diffusion controllability by being dissociated by an acid is attracting attention because it has excellent contrast between exposed and unexposed areas, but there are many development defects and LWR. The characteristics were still insufficient.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide a radiation-sensitive resin composition capable of forming a resist pattern with few development defects and low LWR. To provide things.

  As a result of intensive studies to achieve the above problems, the present inventors have achieved the above problems by including an acid-dissociable group-containing resin, a radiation-sensitive acid generator, and a compound having a predetermined structure. As a result, the present invention has been completed.

  That is, according to this invention, the radiation sensitive resin composition shown below is provided.

  [1] (A) an acid dissociable group-containing resin (hereinafter also referred to as “resin (A)”) and (B) a radiation-sensitive acid generator (hereinafter also referred to as “acid generator (B)”) (C) The radiation sensitive resin composition containing the compound (henceforth "compound (C)") represented by the following general formula (i).

(Wherein in formula (i), R ¹ is a monovalent hydrocarbon group substituted carbon atoms and optionally 1 to 20, a monovalent organic group having a thiophenyl group, or a lactone structure, R ² Represents a single bond, —O—, —COO—, —OCO—, —S—, or a single bond, R ³ represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, and a represents 0 to And R ² and R ³ may be the same or different when there are a plurality of R ² and R ³ , and X ⁺ represents an onium cation.)

[2] X ⁺ in the general formula (i) is at least one selected from an onium cation represented by the following general formula (1-1) and an onium cation represented by the following general formula (1-2). The radiation-sensitive resin composition according to [1].

In the general formulas (1-1) and (1-2), R ^{4 to} R ⁸ are each independently a hydrogen atom, a hydroxyl group, a nitro group, a halogen atom, or an optionally substituted carbon atom having 1 to 1 carbon atoms. An alkyl group having 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkoxyl group having 1 to 10 carbon atoms;

  [3] The above [1] or [2], wherein the resin (A) has a repeating unit represented by the following general formula (2) (hereinafter also referred to as “repeating unit (2)”). Radiation sensitive resin composition.

In the general formula (2), R ⁹ represents a hydrogen atom, a methyl group or a trifluoromethyl group, and R ¹⁰ is an alkyl group having 1 to 4 carbon atoms or a monovalent alicyclic group having 4 to 20 carbon atoms. Represents a hydrocarbon group, and two R ^{11 s} each independently represent a C 1-4 alkyl group or a C 4-20 monovalent alicyclic hydrocarbon group, or two R ¹¹ Are bonded to each other and represent a divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms formed together with the carbon atom to which they are bonded.

  The radiation-sensitive resin composition of the present invention has an effect that a resist pattern with few development defects and a small LWR can be formed.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that modifications, improvements, and the like appropriately added to the embodiments described above fall within the scope of the present invention.

  The radiation sensitive resin composition of this invention contains resin (A), an acid generator (B), and a compound (C). Hereinafter, each component will be described.

1 (A) Acid-dissociable group-containing resin Resin (A) is a polymer that is insoluble or hardly soluble in alkali, but has a protecting group (acid-dissociable group) that can be removed by the action of an acid, It is a polymer that exhibits alkali solubility due to elimination of a protecting group by the action of an acid. The term “alkali insoluble or hardly soluble in alkali” as used herein refers to alkali development conditions employed when forming a resist pattern from a resist film formed using a radiation-sensitive resin composition containing the resin (A). Below, when a 100 nm-thick film using only the resin (A) is developed instead of the resist film, 50% or more of the initial film thickness remains after development.

  The resin (A) has a repeating unit having an acid dissociable group. A preferred example of the repeating unit having such an acid dissociable group is the repeating unit (2).

Among the groups represented by R ¹⁰ and R ¹¹ in the general formula (2), specifically, as an alkyl group having 1 to 4 carbon atoms, specifically, a methyl group, an ethyl group, an n-propyl group, an i-propyl group , N-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group and the like. Specific examples of the monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms include cycloalkyl groups such as a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; dicyclopentanyl And groups having a bridged alicyclic skeleton such as a group, a dicyclopentenyl group, a tricyclodecyl group, a tetracyclododecyl group, and an adamantyl group. Further, as the divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, which is formed together with the carbon atom to which the two R ¹¹ are bonded to each other, specifically, the carbon number 4 The group which remove | eliminated one hydrogen atom from the monovalent | monohydric alicyclic hydrocarbon group of -20 can be mentioned.

  Preferable examples of the repeating unit (2) include repeating units represented by general formulas (2-1) to (2-15).

In general formulas (2-1) to (2-15), R ⁹ represents a hydrogen atom, a methyl group or a trifluoromethyl group.

The resin (A) may have other repeating units. Preferable examples of other repeating units include repeating units having a lactone skeleton. Examples of the repeating unit having a lactone skeleton include (meth) acrylic acid-5-oxo-4-oxa-tricyclo [4.2.1.0 ^3,7 ] non-2-yl ester, (meth) acrylic acid. -9-methoxycarbonyl-5-oxo-4-oxa-tricyclo [4.2.1.0 ^3,7 ] non-2-yl ester, (meth) acrylic acid-5-oxo-4-oxa-tricyclo [ 5.2.1.0 ^3,8 ] dec-2-yl ester, (meth) acrylic acid-10-methoxycarbonyl-5-oxo-4-oxa-tricyclo [5.2.1.0 ^3,8 ] Dec-2-yl ester, (meth) acrylic acid-6-oxo-7-oxa-bicyclo [3.2.1] oct-2-yl ester, (meth) acrylic acid-4-methoxycarbonyl-6-oxo −7− Oxa-bicyclo [3.2.1] oct-2-yl ester, (meth) acrylic acid-7-oxo-8-oxa-bicyclo [3.3.1] non-2-yl ester, (meth) acrylic Acid-4-methoxycarbonyl-7-oxo-8-oxa-bicyclo [3.3.1] non-2-yl ester, (meth) acrylic acid-2-oxotetrahydropyran-4-yl ester, (meth) Acrylic acid-4-methyl-2-oxotetrahydropyran-4-yl ester, (meth) acrylic acid-4-ethyl-2-oxotetrahydropyran-4-yl ester, (meth) acrylic acid-4-propyl-2 -Oxotetrahydropyran-4-yl ester, (meth) acrylic acid-5-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid-2,2-di Methyl-5-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid-4,4-dimethyl-5-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid-2-oxotetrahydrofuran-3-yl ester, (Meth) acrylic acid-4,4-dimethyl-2-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid-5,5-dimethyl-2-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid- 2-oxotetrahydrofuran-3-yl ester, (meth) acrylic acid-5-oxotetrahydrofuran-2-ylmethyl ester, (meth) acrylic acid-3,3-dimethyl-5-oxotetrahydrofuran-2-ylmethyl ester, (Meth) acrylic acid-4,4-dimethyl-5-oxote There are Rahidorofuran 2-yl repeating unit derived from a compound such as methyl ester.

  Further, the resin (A) may further have other repeating units. Furthermore, as other repeating units, there are other repeating units derived from (meth) acrylic acid esters. More specifically, hydroxyl group-containing (meth) acrylic acid esters, carboxyl group-containing (meth) acrylic acid esters, etc. Can be mentioned.

  In the resin (A), the content of the repeating unit (2) with respect to all repeating units is preferably 20 to 80 mol%, particularly preferably 25 to 75 mol%. When the content ratio of the repeating unit (2) is less than 20 mol%, sufficient solubility may not be obtained and resolution may be deteriorated. On the other hand, if it exceeds 80 mol%, the adhesion to the substrate may deteriorate.

(Method for preparing resin (A))
The method for preparing the resin (A) is not particularly limited. For example, a polymerizable unsaturated monomer corresponding to each repeating unit constituting a desired molecular composition is converted into a radical polymerization initiator and a chain transfer agent. In the presence of the above, it can be prepared by polymerization in a suitable solvent. The radical polymerization initiator is preferably added in an amount that provides a sufficiently high concentration in order to achieve a sufficient polymerization rate. However, if the ratio of the addition amount of the radical polymerization initiator to the addition amount of the chain transfer agent is too high, a radical-radical coupling reaction occurs, and an undesirable non-living radical polymer is generated. A polymer having uncontrolled properties in the polymer properties is obtained. Therefore, the molar ratio of the addition amount of the radical polymerization initiator and the addition amount of the chain transfer agent (radical polymerization initiator: chain transfer agent) is preferably 1: 1 to 0.005: 1.

  Although it does not specifically limit as a radical polymerization initiator, There exist a thermal-polymerization initiator, a redox polymerization initiator, and a photoinitiator. Specifically, peroxide initiators such as t-butyl hydroperoxide, t-butyl perbenzoate, and benzoyl peroxide; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azo Examples thereof include azo compounds such as bisisobutyronitrile (AIBN), 1,1′-azobis (cyclohexanecarbonitrile), and dimethyl-2,2′-azobisisobutyrate (MAIB). Examples of chain transfer agents include pyrazole derivatives and alkylthiols.

  About superposition | polymerization operation, it can carry out by methods, such as normal batch polymerization and dripping polymerization. For example, the polymerizable unsaturated monomer corresponding to the repeating unit (2), other repeating units, and other repeating units is dissolved in an organic solvent and polymerized in the presence of a radical polymerization initiator and a chain transfer agent. Thus, the resin (A) can be prepared. As the polymerization solvent, an organic solvent that can dissolve the polymerizable unsaturated monomer, radical polymerization initiator, and chain transfer agent is generally used. Examples of such organic solvents include ketone solvents, ether solvents, aprotic polar solvents, ester solvents, aromatic solvents, and linear or cyclic aliphatic solvents.

  Specific examples of the ketone solvent include methyl ethyl ketone and acetone. Specific examples of the ether solvent include alkoxyalkyl ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, and 1,4-dioxane. Specific examples of the aprotic polar solvent include dimethylformamide and dimethylsulfoxide. Specific examples of the ester solvent include alkyl acetates such as ethyl acetate and methyl acetate. Specific examples of the aromatic solvent include alkylaryl solvents, that is, halogenated aromatic solvents such as toluene, xylene, and chlorobenzene. Specific examples of the aliphatic solvent include hexane and cyclohexane.

  The polymerization temperature is generally 20 to 120 ° C, preferably 50 to 110 ° C, and more preferably 60 to 100 ° C. The polymerization reaction may be performed in a normal air atmosphere, but it is preferably performed in an inert gas atmosphere such as nitrogen or argon. Furthermore, the polymerization time is generally 0.5 to 144 hours, preferably 1 to 72 hours, and more preferably 2 to 24 hours.

  The resin (A) may have a residue derived from a chain transfer agent at the end of the molecular chain, may not have a residue derived from the chain transfer agent at the end of the molecular chain, It may be in a state in which a part of the residue derived from the chain transfer agent remains.

  The resin (A) is naturally low in impurities such as halogen and metal, but the residual monomer or oligomer component is preferably not more than a predetermined value, for example, 0.1% by mass or less by HPLC analysis. . This is not only to further improve the sensitivity, resolution, process stability, pattern shape, etc. as a resist, but also to produce a radiation-sensitive resin composition that can be used as a resist with little change over time, such as foreign matter in liquid or sensitivity. Because you can.

  Examples of the purification method of the resin (A) include the following methods. As a method of removing impurities such as metals, a method of adsorbing metals in the resin (A) solution using a zeta potential filter, or washing the resin (A) solution with an acidic aqueous solution such as oxalic acid or sulfonic acid. There is a method of removing a metal in a chelated state. In addition, as a method of removing residual monomers and oligomer components below a specified value, liquid-liquid extraction method that removes residual monomers and oligomer components by combining water washing and an appropriate solvent, components having a specific molecular weight or less A purification method in the state of solution such as ultrafiltration that extracts and removes only the residual monomer by coagulating the resin (A) in the poor solvent by dropping the resin (A) solution into the poor solvent There are a reprecipitation method and a purification method in a solid state such as washing the filtered polymer slurry with a poor solvent. Moreover, it can also carry out combining these methods. In addition, the poor solvent used in the reprecipitation method depends on the physical properties of the resin (A) to be purified and cannot be generally exemplified. However, those skilled in the art appropriately select according to the physical properties of the polymer. can do.

  The weight average molecular weight (hereinafter referred to as “Mw”) in terms of polystyrene by gel permeation chromatography (GPC) of the resin (A) is usually 1,000 to 300,000 and 2,000 to 300,000. It is preferably 2,000 to 12,000. If the Mw of the resin (A) is less than 1,000, the heat resistance as a resist may decrease. On the other hand, if it exceeds 300,000, developability as a resist may be lowered. The ratio (Mw / Mn) of Mw of the resin (A) to polystyrene-reduced number average molecular weight (hereinafter referred to as “Mn”) by gel permeation chromatography (GPC) is preferably 1 to 5, 1 to 3 is more preferable, and 1 to 1.6 is particularly preferable. In addition, the molecular weight of resin (A) can be adjusted by controlling the ratio of the usage-amount of a monomer and the usage-amount of a chain transfer agent.

2 (B) Radiation-sensitive acid generator The acid generator (B) is a compound capable of generating an acid when irradiated with radiation. In this specification, actinic rays such as far ultraviolet rays represented by KrF excimer laser (wavelength 248 nm) or ArF excimer laser (wavelength 193 nm) are also included in the concept of “radiation” for convenience.

  Examples of the acid generator (B) include onium salts such as sulfonium salts and iodonium salts, organic halogen compounds, and sulfone compounds such as disulfones and diazomethane sulfones. Specific examples of the acid generator (B) include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, triphenylsulfonium 2 -Triphenylsulfonium salts such as bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium camphorsulfonate;

  4-cyclohexylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2. 2.1] 4-cyclohexylphenyldiphenylsulfonium salts such as hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium camphorsulfonate;

  4-methanesulfonylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium 2- 4-methanesulfonylphenyl diphenylsulfonium salts such as bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium camphorsulfonate;

  Diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium perfluoro-n-octanesulfonate, diphenyliodonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2, Diphenyliodonium salts such as 2-tetrafluoroethanesulfonate and diphenyliodonium camphorsulfonate;

  Bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, bis (4-t-butylphenyl) iodonium perfluoro-n-octanesulfonate, Bis (4-t-butylphenyl) iodonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, bis (4-t-butylphenyl) iodonium camphor Bis (4-tert-butylphenyl) iodonium salts such as sulfonates;

  1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, (4-n-Butoxynaphthalen-1-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 2-bicyclo [2.2. 1] 1- (4-n-) such as hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium camphorsulfonate Butoxynaphthalen-1-yl) tetrahydrothiophenium salt;

  1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, (6-n-Butoxynaphthalen-2-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium 2-bicyclo [2.2. 1] 1- (4-n-) such as hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium camphorsulfonate Butoxynaphthalen-1-yl) tetrahydrothiophenium salt;

  1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, (3,5-Dimethyl-4-hydroxyphenyl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium 2-bicyclo [2.2. 1] 1- (3,5- such as hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium camphorsulfonate Dimethyl-4-hydroxyphenyl) tetrahydrothiol Salt;

N- (trifluoromethanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, N- (nonafluoro-n-butanesulfonyloxy) bicyclo [2.2.1] hept -5-ene-2,3-dicarboximide, N- (perfluoro-n-octanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, N- ( 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboxy imide, N- (2- (3- tetracyclo ^[6.2.1.1 3,6 ^{.0 2,7]} dodecanyl) -1,1-difluoroethane-sulfonyloxy) bicyclo [2.2.1] hept - Bicyclo [2.2.1] such as 5-ene-2,3-dicarboximide, N- (camphorsulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide And hept-5-ene-2,3-dicarboximide.

  An acid generator (B) can be used individually by 1 type or in mixture of 2 or more types. The content of the acid generator (B) is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the resin (A) from the viewpoint of ensuring sensitivity and developability as a resist. More preferably, it is 1-20 mass parts. When the content of the acid generator (B) is less than 0.1 parts by mass, sensitivity and developability may be deteriorated. On the other hand, if it exceeds 30 parts by mass, the transparency to radiation is lowered, and it tends to be difficult to obtain a rectangular resist pattern.

3 (C) Compound Represented by General Formula (i) The compound (C) is a compound represented by the general formula (i), and an acid pKa generated by exposure is generated from the acid generator (B). It is preferably higher than the pKa of the acid. That is, a compound that generates an acid weaker than an acid generated from the acid generator (B) by exposure is preferable.
The acid generated by exposure from the acid generator (B) preferably has a pKa of 2 or less, and the compound (C) in the non-irradiated part undergoes an ion exchange reaction with the acid generated from the acid generator (B), It has the effect of suppressing the acid diffusion phenomenon. On the other hand, in the radiation irradiated part, the compound (C) loses basicity to the acid generated from the acid generator (B) by being decomposed. Therefore, when the radiation-sensitive resin composition of the present invention containing the compound (C) is used, good contrast can be obtained in the irradiated portion and the non-irradiated portion.

Among the groups represented by R ¹ and R ³ in the general formula (i), the monovalent hydrocarbon group having 1 to 20 carbon atoms includes a methyl group, an ethyl group, an n-propyl group, and an i-propyl group. , N-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-pentyl group, i-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group Linear or branched alkyl groups such as n-decyl group; cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group; dicyclopentanyl group, dicyclopentenyl group, A group having a bridged alicyclic skeleton such as a tricyclodecyl group, a tetracyclododecyl group or an adamantyl group; an alkylcycloalkyl group such as a methylcyclohexyl group or an ethylcyclohexyl group; Groups having an alkyl-substituted bridged alicyclic skeleton such as adamantyl group; aryl groups such as phenyl group, biphenyl group, naphthyl group, anthryl group; benzyl group, phenylethyl group, phenylpropyl group, naphthylmethyl group, naltylethyl group And the like, and the like. Among them, as R ¹ , a phenyl group, a biphenyl group, a naphthyl group and the like are preferable, and a phenyl group is particularly preferable. As R ³ , a methyl group, an ethyl group, an n-propyl group, an i-propyl group, and the like are preferable. Particularly preferred is a methyl group.
R ² is preferably —COO—.

  Preferable examples of compound (C) include compounds represented by general formulas (i-1) to (i-37).

一般式（ｉ−１）〜（ｉ−３７）中、Ｘ^＋は、オニウムカチオンを示す。

In the general formulas (i-1) to (i-37), X ⁺ represents an onium cation.

In the general formula (i) and the general formulas (i-1) to (i-37), the onium cation represented by X ⁺ is represented by at least one of the general formulas (1-1) and (1-2). It is preferable that it is an onium cation.

In general formulas (1-1) and (1-2), R ^{4 to} R ⁸ are each independently a hydrogen atom, a hydroxyl group, a nitro group, a halogen atom, or an optionally substituted carbon atom having 1 to 10 carbon atoms. An alkyl group, a cycloalkyl group having 3 to 12 carbon atoms, or an alkoxyl group having 1 to 10 carbon atoms.

  Specific examples of the sulfonium cation represented by the general formula (1-1) include sulfonium cations represented by the formulas (1-1-1) to (1-1-21). Specific examples of the iodonium cation represented by the general formula (1-2) include iodonium cations represented by the formulas (1-2-1) to (1-227).

In the general formula (i), a monovalent onium cation represented as X ⁺ is described in, for example, Advances in Polymer Science, Vol. 62, p. It can be synthesized according to the general method described in 1-48 (1984).

  A compound (C) can be used individually by 1 type or in mixture of 2 or more types. The content of the compound (C) is preferably 0.001 to 20 parts by mass and more preferably 0.001 to 12 parts by mass with respect to 100 parts by mass of the resin (A). When the content of the compound (C) is less than 0.001 part by mass, the sensitivity as a resist and the developability of an exposed region may be deteriorated. On the other hand, if it exceeds 20 parts by mass, the pattern shape and dimensional fidelity as a resist may be lowered depending on the process conditions.

4 Other components The radiation-sensitive resin composition of the present invention may contain other additives such as other acid diffusion control agents, alicyclic additives, surfactants, and sensitizers as necessary. It can contain as.

  Since compound (C) itself has acid diffusion controllability, good resolution, pattern shape, and LWR characteristics can be obtained without using other acid diffusion control agents in combination. Absent. As other acid diffusion controlling agents, other nitrogen-containing organic compounds other than the compound (C) are preferably used.

  As such a nitrogen-containing organic compound, for example, a compound represented by the general formula (3) (hereinafter referred to as “nitrogen-containing compound (I)”), a compound having two nitrogen atoms in the same molecule (hereinafter referred to as “nitrogen-containing compound (I)”) "Nitrogen-containing compound (II)"), polyamino compound having three or more nitrogen atoms in the same molecule and polymer thereof (hereinafter collectively referred to as "nitrogen-containing compound (III)"), amide group-containing compound , Urea compounds, nitrogen-containing heterocyclic compounds, and the like.

In general formula (3), several R <^12> shows a hydrogen atom, the linear, branched or cyclic alkyl group which may be substituted, an aryl group, or an aralkyl group mutually independently.

  Examples of the nitrogen-containing compound (I) include mono (cyclo) alkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, cyclohexylamine; di-n- Butylamine, di-n-pentylamine, di-n-hexylamine, di-n-heptylamine, di-n-octylamine, di-n-nonylamine, di-n-decylamine, cyclohexylmethylamine, dicyclohexylamine, etc. Di (cyclo) alkylamines; triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine , Tri-n-nonylamine, tri-n-decylamine, cyclohexyl Tri (cyclo) alkylamines such as dimethylamine, methyldicyclohexylamine, tricyclohexylamine; substituted alkylamines such as 2,2 ′, 2 ″ -nitrotriethanol; aniline, N-methylaniline, N, N-dimethyl Aniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, 4-nitroaniline, diphenylamine, triphenylamine, naphthylamine, 2,4,6-tri-tert-butyl-N-methylaniline, N-phenyl Aromatics such as diethanolamine, 2,6-diisopropylaniline, 2- (4-aminophenyl) -2- (3-hydroxylphenyl) propane, 2- (4-aminophenyl) -2- (4-hydroxyphenyl) propane There are amines.

  Examples of the nitrogen-containing compound (II) include ethylenediamine, N, N, N ′, N′-tetramethylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, and 4,4′-diaminodiphenylether. 4,4′-diaminobenzophenone, 4,4′-diaminodiphenylamine, 2,2-bis (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, , 4-bis [1- (4-aminophenyl) -1-methylethyl] benzene, 1,3-bis [1- (4-aminophenyl) -1-methylethyl] benzene, bis (2-dimethylaminoethyl) ) Ether, bis (2-diethylaminoethyl) ether, 1- (2-hydroxyethyl) -2-y Dazorijinon, 2 quinoxalinium linoleic, N, N, N ', there is N'- tetrakis (2-hydroxypropyl) ethylenediamine and the like.

  Examples of the nitrogen-containing compound (III) include polyethyleneimine, polyallylamine, 2-dimethylaminoethylacrylamide polymer, and the like.

  Examples of the amide group-containing compound include Nt-butoxycarbonyldi-n-octylamine, Nt-butoxycarbonyldi-n-nonylamine, Nt-butoxycarbonyldi-n-decylamine, Nt- Butoxycarbonyldicyclohexylamine, Nt-butoxycarbonyl-1-adamantylamine, Nt-butoxycarbonyl-2-adamantylamine, Nt-butoxycarbonyl-N-methyl-1-adamantylamine, (S)-( -)-1- (t-butoxycarbonyl) -2-pyrrolidinemethanol, (R)-(+)-1- (t-butoxycarbonyl) -2-pyrrolidinemethanol, Nt-butoxycarbonyl-4-hydroxypiperidine Nt-butoxycarbonylpyrrolidine, Nt-butoxycarbonyl Perazine, N, N-di-t-butoxycarbonyl-1-adamantylamine, N, N-di-t-butoxycarbonyl-N-methyl-1-adamantylamine, Nt-butoxycarbonyl-4,4′- Diaminodiphenylmethane, N, N′-di-t-butoxycarbonylhexamethylenediamine, N, N, N ′, N′-tetra-t-butoxycarbonylhexamethylenediamine, N, N, N ′, N ″, N '' -Pentamethyldiethylenetriamine,

  N, N′-di-t-butoxycarbonyl-1,7-diaminoheptane, N, N′-di-t-butoxycarbonyl-1,8-diaminooctane, N, N′-di-t-butoxycarbonyl- 1,9-diaminononane, N, N′-di-t-butoxycarbonyl-1,10-diaminodecane, N, N′-di-t-butoxycarbonyl-1,12-diaminododecane, N, N′-di -T-butoxycarbonyl-4,4'-diaminodiphenylmethane, Nt-butoxycarbonylbenzimidazole, Nt-butoxycarbonyl-2-methylbenzimidazole, Nt-butoxycarbonyl-2-phenylbenzimidazole, N In addition to Nt-butoxycarbonyl group-containing amino compounds such as -t-butoxycarbonylpyrrolidine, formamide, N- Tylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, benzamide, pyrrolidone, N-methylpyrrolidone, N-acetyl-1-adamantylamine, isocyanuric acid tris (2 -Hydroxyethyl) and the like.

  Examples of urea compounds include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, tri-n-butylthiourea. Etc.

  Examples of the nitrogen-containing heterocyclic compound include imidazole, 4-methylimidazole, 4-methyl-2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2- Imidazoles such as methyl-1H-imidazole; pyridine, 2-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 4-ethylpyridine, 2-phenylpyridine, 4-phenylpyridine, 2-methyl-4-phenylpyridine , Nicotine, nicotinic acid, nicotinic acid amide, quinoline, 4-hydroxyquinoline, 8-oxyquinoline, acridine, pyridines such as 2,2 ′: 6 ′, 2 ″ -terpyridine; piperazine, 1- (2-hydroxy In addition to piperazines such as ethyl) piperazine, Gin, pyrazole, pyridazine, quinosaline, purine, pyrrolidine, piperidine, piperidine ethanol, 3-piperidino-1,2-propanediol, morpholine, 4-methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine, 3 -(N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane and the like.

  The content of the nitrogen-containing organic compound is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of the resin (A). preferable. In addition, although the lower limit of content of a nitrogen-containing organic compound is not specifically limited, Usually, it is 0.001 mass part or more. When the content of the nitrogen-containing organic compound is more than 15 parts by mass, the sensitivity as a resist and the developability of the exposed region may be deteriorated. On the other hand, if it is less than 0.001 part by mass, the pattern shape and dimensional fidelity as a resist may be lowered depending on the process conditions.

  The alicyclic additive may have an acid dissociable group, and is a component that exhibits an action of further improving dry etching resistance, pattern shape, adhesion to a substrate, and the like.

  Examples of the alicyclic additives include 1-adamantanecarboxylic acid t-butyl, 1-adamantanecarboxylic acid t-butoxycarbonylmethyl, 1-adamantanecarboxylic acid α-butyrolactone ester, 1,3-adamantane dicarboxylic acid di-t- Butyl, 1-adamantane acetate t-butyl, 1-adamantane acetate t-butoxycarbonylmethyl, 1,3-adamantanediacetate di-t-butyl, 2,5-dimethyl-2,5-di (adamantylcarbonyloxy) hexane Adamantane derivatives such as;

  Deoxycholate t-butyl, deoxycholate t-butoxycarbonylmethyl, deoxycholate 2-ethoxyethyl, deoxycholate 2-cyclohexyloxyethyl, deoxycholate 3-oxocyclohexyl, deoxycholate tetrahydropyranyl, deoxychol Deoxycholic acid esters such as acid mevalonolactone ester; t-butyl lithocholic acid, t-butoxycarbonylmethyl lithocholic acid, 2-ethoxyethyl lithocholic acid, 2-cyclohexyloxyethyl lithocholic acid, 3-oxocyclohexyl lithocholic acid, lithocholic acid Examples thereof include lithocholic acid esters such as tetrahydropyranyl acid acid and mevalonolactone ester of lithocholic acid. In addition, an alicyclic additive can be used individually by 1 type or 2 or more types.

  Also, for example, an additive having the same function as an alicyclic additive such as dimethyl adipate, diethyl adipate, dipropyl adipate, di-n-butyl adipate, di-t-butyl adipate, and the like Can be used as

  A surfactant is a component that exhibits an effect of improving coating properties, striation, developability, and the like. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, polyethylene glycol In addition to nonionic surfactants such as distearate, hereinafter, all trade names are KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75, no. 95 (above, manufactured by Kyoeisha Chemical Co., Ltd.), Ftop EF301, EF303, EF352 (above, manufactured by Tochem Products), Megafax F171, F173 (above, manufactured by Dainippon Ink and Chemicals), Florad FC430, FC431 (above, manufactured by Sumitomo 3M), Asahi Guard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, SC-106 ( As mentioned above, manufactured by Asahi Glass Co., Ltd.). In addition, surfactant can be used individually by 1 type or 2 types or more. Moreover, it is preferable that content of surfactant is 2 mass parts or less with respect to 100 mass parts of resin (A).

  The sensitizer absorbs the energy of radiation and transmits the energy to the acid generator (B), thereby increasing the amount of acid produced, thereby increasing the apparent sensitivity of the radiation-sensitive resin composition. It is a component having the effect of improving. Examples of the sensitizer include carbazoles, benzophenones, rose bengals, anthracenes, phenols and the like. In addition, a sensitizer can be used individually by 1 type or 2 or more types. Moreover, it is preferable that content of a sensitizer is 50 mass parts or less with respect to 100 mass parts of resin (A).

(Preparation of radiation-sensitive resin composition)
When the radiation-sensitive resin composition of the present invention is used, it is usually dissolved in a solvent so that the total solid content concentration is 1 to 50% by mass, preferably 3 to 25% by mass. It filters with a filter of about 2 micrometers, and is prepared as a solution of a radiation sensitive resin composition. Examples of the solvent used for preparing the solution of the radiation sensitive resin composition include linear or branched ketones such as 2-pentanone, 2-hexanone, 2-heptanone, and 2-octanone; cyclopentanone Cyclic ketones such as cyclohexanone; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; 2-hydroxypropions such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate In addition to alkyl 3-alkoxypropionates such as methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate and ethyl 3-ethoxypropionate, ethylene glycol Monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, n-butyl acetate, methyl pyruvate, pyruvin Examples include ethyl acid, N-methylpyrrolidone, and γ-butyrolactone.

  These solvents can be used alone or in combination of two or more. Among these, at least one selected from the group consisting of propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 2-heptanone, cyclohexanone, γ-butyrolactone, ethyl 2-hydroxypropionate and ethyl 3-ethoxypropionate is used. It is preferable.

  The radiation-sensitive resin composition of the present invention thus prepared can be suitably used for forming a resist film using spin coating or the like in photolithography that is generally performed.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

  [Weight average molecular weight (Mw) and number average molecular weight (Mn)]: GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) manufactured by Tosoh Corporation, flow rate: 1.0 ml / min, elution solvent: tetrahydrofuran, column temperature : Measured by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard under analysis conditions of 40 ° C. The degree of dispersion (Mw / Mn) was calculated from the measurement results.

[ ¹³ C-NMR and ¹ H-NMR analysis]: ¹³ C-NMR analysis and ¹ H-NMR analysis were measured using “JNM-EX270” manufactured by JEOL Ltd.

(Synthesis Example 1 Synthesis of Compound (C-1))
20 g of ion exchange resin (QAE Sephadex A-25) manufactured by GE Healthcare Biosciences was swollen with ultrapure water all day and night, and then filled into a column tube. A solution obtained by dissolving 28 g of sodium benzenesulfinic acid salt represented by the formula (X-1) in methanol was poured into a column tube filled with an ion exchange resin, and the sulfin anion was supported on the ion exchange resin. After flashing back with a sufficient amount of methanol, a solution of 5.2 g of triphenylsulfonium chloride dissolved in methanol was poured into the column tube to carry out an anion exchange reaction. The solvent of the obtained solution was distilled off with an evaporator and then dried overnight at room temperature to obtain a compound represented by formula (C-1) (hereinafter referred to as “compound (C-1)”) (yield). 7.0 g).

(Synthesis Example 2 Synthesis of Compound (C-2))
20 g of ion exchange resin (QAE Sephadex A-25) manufactured by GE Healthcare Biosciences was swollen with ultrapure water all day and night, and then filled into a column tube. A solution obtained by dissolving 28 g of sodium benzenesulfinic acid salt represented by the formula (X-1) in methanol was poured into a column tube filled with an ion exchange resin, and the sulfin anion was supported on the ion exchange resin. After flashing back with a sufficient amount of methanol, a solution of 5.6 g of diphenyliodonium chloride dissolved in methanol was poured into the column tube to carry out an anion exchange reaction. The solvent of the obtained solution was distilled off with an evaporator and then dried overnight at room temperature to obtain a compound represented by the formula (C-2) (hereinafter referred to as “compound (C-2)”) (yield). 7.1 g).

  Hereinafter, synthesis examples of the resin (A) will be described. In addition, the kind of monomer used for the synthesis | combination of resin (A) is shown below as Formula (M-1)-(M-9).

(Synthesis Example 3 Preparation of Resin (A-1))
13.0 g (50 mol%) of a monomer represented by the formula (M-1) (hereinafter also referred to as “monomer (M-1)”), a monomer represented by the formula (M-7) (Hereinafter also referred to as “monomer (M-7)”) 2.9 g (10 mol%) and a monomer represented by formula (M-9) (hereinafter “monomer (M-9)”) A monomer solution was prepared by dissolving 10.3 g (30 mol%) in 60 g of 2-butanone and adding 1.3 g of dimethylazobisisobutyronitrile. On the other hand, a monomer represented by the formula (M-5) (hereinafter also referred to as “monomer (M-5)”) 3.8 g (10 mol%) dissolved in 30 g of 2-butanone The body solution was put into a 200 ml three-necked flask and purged with nitrogen for 30 minutes, and then the reaction kettle was heated to 80 ° C. with stirring, and the monomer solution prepared in advance was dropped over 3 hours using a dropping funnel. . The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After the completion of the polymerization, the polymerization solution was cooled with water to 30 ° C. or less, poured into 600 g of methanol, and the precipitated white powder was filtered off. The filtered white powder was washed twice with 150 g of methanol in the form of a slurry and then filtered again and dried at 50 ° C. for 17 hours to obtain a white powder copolymer. Mw of the obtained copolymer was 6698, Mw / Mn was 1.40, the yield was 75.3%, and the ratio of repeating units derived from each monomer in the copolymer ( The monomer (M-1) / monomer (M-5) / monomer (M-7) / monomer (M-9)) are mol%, 49.0 / 9.2 / 10. 1 / 31.6. This copolymer is referred to as “resin (A-1)”. Table 1 shows the types of monomers used in Synthesis Example 1 and the formulation. In addition, Table 2 shows the measurement results of Mw, Mw / Mn, yield, and the ratio of repeating units derived from each monomer in the copolymer.

(Synthesis Examples 4 to 13 Synthesis of Resins (A-2) to (A-11))
A copolymer was prepared in the same manner as in Synthesis Example 3 except that the types of monomers shown in Table 1 were used in the formulation shown in Table 1. In addition, Table 2 shows the measurement results of Mw, Mw / Mn, yield of the obtained copolymer, and the ratio of the repeating unit derived from each monomer in the copolymer. Let each copolymer be resin (A-2)-(A-11).

(Example 1 Preparation of radiation-sensitive resin composition)
100 parts of resin (A-1) prepared in Synthesis Example 3, 7.0 parts of acid generator (B-1), 5.2 parts of compound (C-1) synthesized in Synthesis Example 1, solvent (E-1) ) 1700 parts, 700 parts of solvent (E-2), and 30 parts of solvent (E-3) were mixed to prepare a radiation sensitive resin composition.

(Examples 2-12 and Comparative Examples 1-3 Preparation of Radiation Sensitive Resin Composition)
A radiation sensitive resin composition was prepared in the same manner as in Example 1 except that the formulation shown in Table 3 was used.

  Details of the acid generator (B), the acid diffusion inhibitor (D), and the solvent (E) are shown below.

Acid generator (B)
(B-1): Triphenylsulfonium 2- (adamantanecarbonyloxy) -1,1,2,2-tetrafluorohexane-1-sulfonate

Acid diffusion inhibitor (D)
(D-1): Triphenylsulfonium salicylate (D-2): Nt-butoxycarbonyl-4-hydroxypiperidine

Solvent (E)
(E-1): Propylene glycol monomethyl ether acetate (E-2): Cyclohexanone (E-3): γ-butyrolactone

Evaluation of Radiation Sensitive Resin Composition Various evaluations were performed on the radiation sensitive resin compositions of Examples 1 to 12 and Comparative Examples 1 to 3 as follows. These evaluation results are shown in Table 4.

[Development defects]:
First, a film having a thickness of 110 nm is formed from a radiation-sensitive resin composition on a 12-inch silicon wafer on which an underlayer antireflection film (“ARC66”, manufactured by Nissan Chemical Co., Ltd.) is formed, and soft baking is performed at 110 degrees for 60 seconds. (SB) was performed. Next, this film is exposed through a mask pattern using an ArF excimer laser immersion exposure apparatus (“NSR S610C”, manufactured by NIKON) under the conditions of NA = 1.3, ratio = 0.800, Dipole. did. After the exposure, post-baking (PEB) was performed at 95 ° C. for 60 seconds. Thereafter, the resist film was developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution, washed with water, and dried to form a positive resist pattern. At this time, the exposure amount for forming a line and space having a width of 45 nm was determined as the optimum exposure amount. With this optimum exposure amount, a line and space having a line width of 45 nm was formed on the entire surface of the wafer to obtain a defect inspection wafer. A scanning electron microscope (“CC-4000”, manufactured by Hitachi High-Technologies Corporation) was used for length measurement.

Thereafter, the number of defects on the defect inspection wafer was measured using “KLA2810” manufactured by KLA-Tencor. Furthermore, the defects measured by “KLA2810” were classified into those judged to be resist-derived and foreign matters derived from the outside. After classification, when the total number of defects (number of defects) determined to be derived from the resist film was less than 100 / wafer, it was judged as “good”, and when it exceeded 100 / wafer, it was judged as “bad”.

  [Evaluation of LWR]: A 45 nm (1L / 1S) pattern formed on a resist film on a substrate at an optimum exposure amount is measured from the top of the pattern using a length measurement SEM (manufactured by Hitachi High-Technology Corporation, model number “CG4000”). Observe and measure the diameter at an arbitrary point, and when the measurement variation is expressed by 3σ, the case where it is 4.0 nm or less is evaluated as “good”, and the case where it is over 4.0 nm is regarded as “bad” evaluated.

  As can be seen from Table 4, it was confirmed that the radiation-sensitive resin composition of the present invention can form a resist pattern with fewer development defects and smaller LWR than Comparative Examples 1 to 3.

  The radiation-sensitive resin composition of the present invention can be suitably used for photoresists that require increasingly finer line widths of resist patterns in the future.

Claims (3)

(A) an acid dissociable group-containing resin;
(B) a radiation sensitive acid generator;
(C) The radiation sensitive resin composition containing the compound represented by the following general formula (i).

(Wherein in formula (i), R ¹ is a monovalent hydrocarbon group substituted carbon atoms and optionally 1 to 20, a monovalent organic group having a thiophenyl group, or a lactone structure, R ² Represents a single bond, —O—, —COO—, —OCO—, —S—, or a single bond, R ³ represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, and a represents 0 to And R ² and R ³ may be the same or different when there are a plurality of R ² and R ³ , and X ⁺ represents an onium cation.) X ⁺ in the general formula (i) is at least one selected from an onium cation represented by the following general formula (1-1) and an onium cation represented by the following general formula (1-2). 1. The radiation sensitive resin composition according to 1.

(In the general formulas (1-1) and (1-2), R ^{4 to} R ⁸ are each independently a hydrogen atom, a hydroxyl group, a nitro group, a halogen atom, or an optionally substituted carbon atom. Represents an alkyl group having 10 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an alkoxyl group having 1 to 10 carbon atoms.) The radiation sensitive resin composition according to claim 1 or 2, wherein the (A) acid-dissociable group-containing resin has a repeating unit represented by the following general formula (2).

(In the general formula (2), R ⁹ represents a hydrogen atom, a methyl group or a trifluoromethyl group, and R ¹⁰ represents an alkyl group having 1 to 4 carbon atoms or a monovalent alicyclic ring having 4 to 20 carbon atoms. The two R ^{11 s} represent, independently of each other, an alkyl group having 1 to 4 carbon atoms or a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, or two R 11 s. ¹¹ represents a divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms, which is formed together with the carbon atom to which the two are bonded together.