JP2008297381A - Copolymer and radiosensitive resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiosensitive resin composition useful as a chemical amplification type resist. <P>SOLUTION: This copolymer comprises a recurring unit expressed by general formula (1) [wherein, R<SP>1</SP>is a 1-3C linear or branched alkyl; and n<SP>1</SP>is an integer of 1 to 5] and a recurring unit expressed by general formula (2). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is useful for microfabrication using various types of radiation such as deep ultraviolet rays typified by KrF excimer laser, ArF excimer laser, F2 excimer laser, X-rays such as synchrotron radiation, and charged particle beams such as electron beams. The present invention relates to a radiation sensitive resin composition that can be suitably used as a chemically amplified resist.

  In the field of microfabrication represented by the manufacture of integrated circuit elements, in order to obtain a higher degree of integration, recently, lithography technology capable of microfabrication at a level of 0.20 μm or less is required. However, in the conventional lithography process, near ultraviolet rays such as i rays are generally used as radiation, and it is said that fine processing at the subquarter micron level is extremely difficult with this near ultraviolet rays.

  Therefore, in order to enable fine processing at a level of 0.20 μm or less, use of radiation having a shorter wavelength is being studied. Examples of such short-wavelength radiation include an emission line spectrum of a mercury lamp, far-ultraviolet rays typified by an excimer laser, an X-ray, an electron beam, and the like. Among these, a KrF excimer laser (wavelength 248 nm) is particularly preferable. ) Or ArF excimer laser (wavelength 193 nm) has been attracting attention.

  As a resist suitable for such excimer laser irradiation, a component having an acid-dissociable functional group and a component that generates acid upon irradiation with radiation (hereinafter referred to as “exposure”) (hereinafter referred to as “photoacid generator”) Many resists using the chemical amplification effect (hereinafter referred to as “chemically amplified resist”) have been proposed.

  As the chemically amplified resist, for example, a resist containing a polymer having a t-butyl ester group of carboxylic acid or a t-butyl carbonate group of phenol and a photoacid generator has been proposed (see Patent Document 1). ). In this resist, an acid generated by exposure causes the t-butoxycarbonyl group or t-butyl carbonate group present in the polymer to dissociate, and the polymer is an acidic group comprising a carboxyl group or a phenolic hydroxyl group. As a result, it utilizes the phenomenon that the exposed region of the resist film becomes readily soluble in an alkaline developer.

  By the way, many of the conventional chemically amplified resists are based on a phenolic resin. However, in the case of such a resin, if far ultraviolet rays are used as radiation, the far-field is caused by an aromatic ring in the resin. Since ultraviolet rays are absorbed, there is a drawback that the exposed far ultraviolet rays cannot sufficiently reach the lower layer part of the resist film. Therefore, the exposure amount is higher in the upper layer part of the resist film and lower in the lower layer part. There is a problem that the pattern profile of the pattern becomes narrower at the top and becomes thicker as it goes down, and a sufficient resolution cannot be obtained. In addition, when the pattern profile after development has a trapezoidal shape, a desired dimensional accuracy cannot be achieved in the next step, that is, etching or ion implantation, which is a problem. In addition, if the upper side of the pattern profile and the side wall of the pattern profile are not rectangular, the resist disappearance rate due to dry etching is increased, which makes it difficult to control the etching conditions.

  On the other hand, the resist pattern profile can be improved by increasing the radiation transmittance of the resist film. For example, (meth) acrylate resins typified by polymethyl methacrylate are highly transparent to far ultraviolet rays and are very preferable from the viewpoint of radiation transmittance. For example, chemical amplification using methacrylate resins A type resist has been proposed (see Patent Document 2).

  However, although this composition is excellent in terms of microfabrication performance, it does not have an aromatic ring and thus has a drawback of low dry etching resistance. In this case as well, it is difficult to perform highly accurate etching. Therefore, it cannot be said that it has both transparency to radiation and dry etching resistance.

  In addition, for chemically amplified resists, as one of the measures for improving dry etching resistance without impairing transparency to radiation, there is a method of introducing an aliphatic ring instead of an aromatic ring into the resin component in the resist. For example, a chemically amplified resist using a (meth) acrylate resin having an aliphatic ring has been proposed (see Patent Document 3).

  However, in this resist, as the acid dissociable functional group of the resin component, groups that are relatively easily dissociated by conventional acids (for example, acetal functional groups such as tetrahydropyranyl groups) and groups that are relatively difficult to dissociate by acid. (For example, t-butyl functional groups such as t-butyl ester groups and t-butyl carbonate groups) are used, and in the case of the former resin component having an acid-dissociable functional group, basic physical properties of the resist, particularly sensitivity The pattern profile is good, but the storage stability of the composition is difficult, and the latter resin component with acid-dissociable functional groups has good storage stability, but the basic physical properties of the resist. In particular, there is a drawback that the sensitivity and pattern profile are impaired. Furthermore, since an aliphatic ring is introduced into the resin component in the resist, there is a problem that the hydrophobicity of the resin itself becomes very high and adhesion to the substrate becomes insufficient.

  In addition, when a resist pattern is formed using a chemically amplified resist, heat treatment is usually performed after exposure in order to promote dissociation of the acid-dissociable functional group. Normally, when the heating temperature is changed, the resist pattern is changed. It is inevitable that the line width also fluctuates to some extent. However, reflecting the recent miniaturization of integrated circuit elements, development of a resist having a small variation in line width (that is, temperature dependency) with respect to a change in heating temperature after exposure has been strongly demanded. .

  Furthermore, in chemically amplified resists, it is known that photoacid generators have a great influence on the function as a resist. Today, the quantum yield of acid generation by exposure is high, and the sensitivity is high. For this reason, onium salt compounds are widely used as photoacid generators for chemically amplified resists. Examples of the onium salt compound include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium naphthalenesulfonate, cyclohexylmethyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate, and the like, and these conventional onium salt compounds. In general, this method is not satisfactory in terms of sensitivity, and even when the sensitivity is relatively high, it is still not sufficient in terms of resist performance in terms of overall resolution and pattern profile.

Under such circumstances, from the viewpoint of technological development that can respond to the progress of miniaturization in integrated circuit elements, it can be applied to short-wavelength radiation typified by far ultraviolet rays, has high transparency to radiation, and is sensitive. There is a strong demand for a chemically amplified resist having excellent basic physical properties as a resist such as resolution and pattern profile.
JP-B-2-27660 JP-A-4-226461 JP-A-7-234511

  The object of the present invention is high transparency to radiation, not only excellent basic physical properties as a resist such as sensitivity, resolution, focus margin, dry etching resistance, pattern profile, etc., but also excellent performance in contact hole pattern applications. The object is to provide a radiation-sensitive resin composition useful as a chemically amplified resist to be exhibited.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be achieved by the following copolymers and compositions, and have completed the present invention.

  That is, according to the present invention, the following copolymers and compositions are provided.

[1] The repeating unit represented by the following general formula (1) and the repeating unit represented by the following general formula (2) are combined and include more than 90 mol% with respect to all repeating units, and gel permeation chromatography (GPC) ) A polystyrene-free copolymer having a polystyrene equivalent weight average molecular weight of 1,000 to 100,000.

(In Formula (1), R ¹ represents a linear or branched alkyl group having 1 to 3 carbon atoms, and n ¹ represents an integer of 1 to 5.)

[2] Copolymers containing repeating units represented by the following general formulas (1), (2) and (3) and having a polystyrene-reduced weight average molecular weight of 1,000 to 100,000 by gel permeation chromatography (GPC). Polymer.

(In the formulas (1) and (3), R ¹ and R ² each represent a linear or branched alkyl group having 1 to 3 carbon atoms, and n ¹ and n ² each represent an integer of 1 to 5 To express.)

[3] The copolymer according to the above [1] or [2], wherein the repeating unit represented by the general formula (1) is 10 to 60 mol% with respect to all repeating units.

[4] A radiation-sensitive resin composition comprising the copolymer according to any one of [1] to [3], a photoacid generator, and a solvent.

  The radiation-sensitive resin composition of the present invention is useful as a chemically amplified resist sensitive to actinic rays, for example, far-ultraviolet rays represented by KrF excimer laser (wavelength 248 nm) or ArF excimer laser (wavelength 193 nm). It has excellent basic physical properties as a resist including a pattern profile and the like, and can exhibit excellent performance in the depth of focus (DOF) of an isolated hole. An integrated circuit element that is expected to be further miniaturized in the future, as it exhibits excellent performance by combining a specific resin, photoacid generator, and solvent, and also has good adhesion to the substrate and pattern skirt shape. It can be used very suitably for the production of

  Hereinafter, the present invention will be described in detail.

The copolymer in the present invention includes a repeating unit group represented by the general formulas (1) to (2) or a repeating unit group represented by the general formulas (1) to (3). In the repeating unit represented by the general formula (1), R ¹ represents a linear or branched alkyl group having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, or an i-propyl group. Etc. n ¹ represents an integer of 1 to 5, and examples thereof include cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane. The preferred repeating unit (1) is a repeating unit represented by the formula (4), and examples of the particularly preferred repeating unit (1) are listed in the formulas (4-1) to (4-4).

  Among formulas (4-1) to (4-4), formula (4-1) and formula (4-2) are preferable in consideration of the combination of repeating units of the present invention.

In the repeating unit represented by the general formula (3), R ² represents a linear or branched alkyl group having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, or an i-propyl group. Etc. n ² represents an integer of 1 to 5, and examples thereof include cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Preferable repeating unit (3) is a repeating unit represented by formula (5), and examples of particularly preferable repeating unit (3) are shown in formulas (5-1) to (5-4).

  Among the formulas (5-1) to (5-4), the formula (5-1) and the formula (5-2) are preferable in consideration of the combination of the repeating units of the present invention.

  The copolymer of the present invention preferably contains the repeating unit (1) and the repeating unit (2) or the repeating unit (1), the repeating unit (2) and the repeating unit (3). The proportion of the repeating unit (1) is 10 to 60 mol%, preferably 20 to 60 mol%, and the repeating unit (2) is 10 to 60 mol%, preferably based on all repeating units constituting the copolymer. Is 20 to 60 mol%; the repeating unit (3) is 20 to 60 mol%, preferably 30 to 50 mol%. In addition, when it consists of repeating unit (1) and repeating unit (2), repeating unit (1) and repeating unit (2) contain more than 90 mol% with respect to all the repeating units. In this case, the copolymer does not contain nitrogen.

  If the content of the repeating unit (1) is less than 20 mol%, the resolution tends to deteriorate, and if it exceeds 60 mol%, the developability tends to decrease. When the content of the repeating unit (2) is less than 20 mol%, the developability as a resist tends to be lowered, and when it exceeds 60 mol%, the resolution is deteriorated and the solubility in a resist solvent tends to be lowered. When the repeating unit (3) is contained in an amount of 20 mol% or more, the resolution is further improved. On the other hand, when the content of the repeating unit (3) exceeds 60 mol%, the developability tends to be lowered.

  The acrylic polymer of the present invention uses, for example, a radical polymerization initiator such as hydroperoxides, dialkyl peroxides, diacyl peroxides, and azo compounds as a mixture of monomers corresponding to each repeating unit, If necessary, it can be produced by polymerization in an appropriate solvent in the presence of a chain transfer agent.

  Examples of the solvent used for the polymerization include cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, norbornane; ethyl acetate, n-butyl acetate, i-butyl acetate, methyl propionate, propylene glycol monomethyl ether. Saturated carboxylic acid esters such as acetate; alkyl lactones such as γ-butyrolactone; alkyl ketones such as 2-butanone, 2-heptanone and methyl isobutyl ketone; cycloalkyl ketones such as cyclohexanone; 2-propanol, propylene glycol monomethyl Examples include alcohols such as ether.

  These solvents can be used alone or in admixture of two or more.

  Moreover, the reaction temperature in the said superposition | polymerization is 40-120 degreeC normally, Preferably it is 50-100 degreeC, and reaction time is 1-48 hours normally, Preferably it is 1-24 hours.

  The acrylic polymer of the present invention is naturally low in impurities such as halogens and metals, and preferably has residual monomers and oligomer components of a predetermined value or less, for example, 0.1% by mass by HPLC. Thereby, not only can the sensitivity, resolution, process stability, pattern shape and the like as a resist be further improved, but also a radiation-sensitive composition that can be used as a resist that does not change with time such as foreign matter in liquid or sensitivity.

  Examples of the purification method of the acrylic polymer include the following methods. As a method of removing impurities such as metals, the metal is chelated and removed by adsorbing the metal in the resin solution using a zeta potential filter or by washing the resin solution with an acidic aqueous solution such as oxalic acid or sulfonic acid. And the like. In addition, as a method of removing residual monomer and oligomer components below the specified value, liquid-liquid extraction method that removes residual monomer and oligomer components by combining water washing and an appropriate solvent, those with a specific molecular weight or less Refining method in a solution state such as ultrafiltration that only extracts and removes the residual monomer, etc. by dripping the acrylic polymer solution into the poor solvent to coagulate the polymer in the poor solvent There are solid state purification methods such as reprecipitation and washing the filtered polymer slurry with a poor solvent. Moreover, these methods can also be combined. The poor solvent used in the reprecipitation method depends on the physical properties of the acrylic polymer to be purified and cannot be generally exemplified. As appropriate, the poor solvent is selected.

  The weight average molecular weight in terms of polystyrene (hereinafter abbreviated as “Mw”) by gel permeation chromatography (GPC) of the acrylic polymer is usually 1,000 to 300,000, preferably 2,000 to 200,000, More preferably, it is 3,000-100,000. In this case, when the Mw of the acrylic polymer is less than 1,000, the heat resistance as a resist tends to decrease, and when it exceeds 300,000, the developability as a resist tends to decrease.

  The ratio (Mw / Mn) of the acrylic polymer Mw to the polystyrene-equivalent number average molecular weight (hereinafter abbreviated as “Mn”) by gel permeation chromatography (GPC) is usually 1 to 5, preferably 1-3. In addition, Mw and Mn are Tosoh's high-speed GPC apparatus (model “HLC-8120”) and Tosoh's GPC column (trade name “G2000HXL”; 2, “G3000HXL”; 1, “G4000HXL”; 1 This was measured by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard under the analysis conditions of a flow rate of 1.0 ml / min, an elution solvent tetrahydrofuran, and a column temperature of 40 ° C.

  In this invention, an acrylic polymer can be used individually or in mixture of 2 or more types. The acrylic polymer is insoluble in alkali or hardly soluble in alkali, but becomes easily soluble in alkali by the action of an acid. Therefore, it is suitable as an acid-dissociable group-containing resin used for the radiation-sensitive resin composition.

  A radiation-sensitive resin composition can be obtained by using the acrylic polymer as an acid-dissociable group-containing resin and a photoacid generator that is a component that generates an acid upon irradiation with radiation. Examples of the photoacid generator include onium salts such as sulfonium salts and iodonium salts, organic halogen compounds, and sulfone compounds such as disulfones and diazomethane sulfones.

Preferred examples of the photoacid generator include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, triphenylsulfonium 2-bicyclo [2.2. 1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10 ] dodecanyl)- Triphenylsulfonium salt compounds such as 1,1-difluoroethanesulfonate, triphenylsulfonium N, N′-bis (nonafluoro-n-butanesulfonyl) imidate, triphenylsulfonium camphorsulfonate;

4-cyclohexylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2. 2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-cyclohexyl-phenyl diphenyl sulfonium 2- (3-tetracyclo ^[4.4.0.1 2,5 ^{.1 7, 10]} dodecanyl) -1,1-difluoroethanesulfonate, 4-cyclohexyl-phenyl diphenyl sulfonium N, N'-bis (nonafluoro -n- butanesulfonyl) imidate, - and cyclohexyl-phenyl camphorsulfonate 4-cyclohexyl-phenyl diphenyl sulfonium salt compound;

4-t-butylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-t-butylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-t-butylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-t-butylphenyl Diphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-t-butylphenyldiphenylsulfonium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethanesulfonate, 4-t-butylphenyl diphenyl sulfonium N, N'-bis (nonafluoro -n- butanesulfonyl) imidate, 4-t- Butyl phenyl di 4-t-butylphenyl diphenyl sulfonium salt compounds such as E sulfonyl sulfonium camphorsulfonate;

Diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium perfluoro-n-octanesulfonate, diphenyliodonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2, 2-tetrafluoroethane sulfonate, diphenyliodonium 2- (3-tetracyclo ^[4.4.0.1 2,5 ^{.1 7,10]} dodecanyl) -1,1-difluoroethanesulfonate, diphenyliodonium N, N'-bis Diphenyliodonium salt compounds such as (nonafluoro-n-butanesulfonyl) imidate, 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 2 - (3-tetracyclo ^[4.4.0.1 2,5 ^{.1 7,10]} dodecanyl) -1,1-difluoroethanesulfonate, bis (4-t- butylphenyl) iodonium N, N'-bis (nonafluoro -N-butanesulfonyl) imidate, bis (4-t-butylphenyl) iodo Um bis such camphorsulfonate (4-t- butylphenyl) iodonium salt compounds;

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] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethanesulfonate, -(4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium N, N'-bis (nonafluoro-n-butanesulfonyl) imidate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiofe 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium salt compounds such as nium camphorsulfonate;

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] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoro Tansulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium N, N′-bis (nonafluoro-n-butanesulfonyl) imidate, 1- (3,5-dimethyl-4-hydroxyphenyl) ) 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium salt compounds such as tetrahydrothiophenium camphorsulfonate;

N- (trifluoromethanesulfonyloxy) succinimide, N- (nonafluoro-n-butanesulfonyloxy) succinimide, N- (perfluoro-n-octanesulfonyloxy) succinimide, N- (2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethane sulfonyloxy) succinimide, N- (2- (3- tetracyclo ^[4.4.0.1 2,5 ^{.1 7,10]} dodecanyl) Succinimide compounds such as -1,1-difluoroethanesulfonyloxy) succinimide and N- (camphorsulfonyloxy) succinimide;

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 ^[4.4.0.1 2,5 ^{.1 7,10]} 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 compounds.

  In this invention, a photo-acid generator can be used individually or in mixture of 2 or more types. The amount of the photoacid generator used is usually 0.1 to 30 parts by mass, preferably 0.1 to 20 parts per 100 parts by mass of the acrylic polymer, from the viewpoint of ensuring the sensitivity and developability as a resist. Part by mass. In this case, if the amount of the photoacid generator used is less than 0.1 parts by mass, the sensitivity and developability tend to decrease. On the other hand, if it exceeds 30 parts by mass, the transparency to radiation decreases and a rectangular resist is produced. It tends to be difficult to obtain a pattern.

  In the radiation sensitive resin composition of the present invention, an acid diffusion controller, an alicyclic additive having an acid dissociable group, an alicyclic additive not having an acid dissociable group, and a surfactant are included as necessary. Various additives such as a sensitizer can be blended. The acid diffusion controlling agent is a component having an action of controlling an undesired chemical reaction in a non-irradiated region by controlling a diffusion phenomenon of an acid generated from a photoacid generator upon irradiation in a resist film. By blending such an acid diffusion control agent, the storage stability of the resulting radiation-sensitive resin composition is improved, the resolution as a resist is further improved, and the holding time from irradiation to development processing ( The change in the line width of the resist pattern due to the variation in PED) can be suppressed, and a composition having excellent process stability can be obtained. The acid diffusion controller is preferably a nitrogen-containing organic compound whose basicity does not change by irradiation or heat treatment during the resist pattern formation step.

  Examples of such nitrogen-containing organic compounds include “tertiary amine compounds”, “amide group-containing compounds”, “quaternary ammonium hydroxide compounds”, “nitrogen-containing heterocyclic compounds”, and the like.

  Examples of the “tertiary amine compound” include triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n. -Tri (cyclo) alkylamines such as octylamine, tri-n-nonylamine, tri-n-decylamine, cyclohexyldimethylamine, dicyclohexylmethylamine, tricyclohexylamine; aniline, N-methylaniline, N, N-dimethylaniline Aromatic amines such as 2-methylaniline, 3-methylaniline, 4-methylaniline, 4-nitroaniline, 2,6-dimethylaniline, 2,6-diisopropylaniline, diphenylamine, triphenylamine, naphthylamine; Ethanolamine, Alkanolamines such as ethanolaniline; N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine, 1,3-bis [1- ( 4-aminophenyl) -1-methylethyl] benzenetetramethylenediamine, 2,2-bis (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2- (4-aminophenyl) -2- (3-hydroxyphenyl) propane, 2- (4-aminophenyl) -2- (4-hydroxyphenyl) propane, 1,4-bis [1- (4-aminophenyl) -1-methylethyl] benzene, 1,3-bis [1- (4-aminophenyl) -1-methylethyl] benzene, bis (2-dimethyl) Minoechiru) ether, bis (2-diethylaminoethyl) ether.

  Examples of the “amide group-containing compound” include Nt-butoxycarbonyldi-n-octylamine, Nt-butoxycarbonyldi-n-nonylamine, Nt-butoxycarbonyldi-n-decylamine, N- t-butoxycarbonyldicyclohexylamine, Nt-butoxycarbonyl-1-adamantylamine, Nt-butoxycarbonyl-N-methyl-1-adamantylamine, 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-butoxycarbonylhexamethyl Range amine, 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-phenylbenz Imidazole, Nt-butoxycarbonyl-pyrrolidine, Nt-butoxycarbonyl-piperidine, Nt-buto In addition to Nt-butoxycarbonyl group-containing amino compounds such as cycarbonyl-4-hydroxy-piperidine, Nt-butoxycarbonyl-morpholine, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N -Methylacetamide, N, N-dimethylacetamide, propionamide, benzamide, pyrrolidone, N-methylpyrrolidone and the like.

  Examples of the “quaternary ammonium hydroxide compound” include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-n-butylammonium hydroxide, and the like. Examples of the “nitrogen-containing heterocyclic compound” include imidazoles such as imidazole, 4-methylimidazole, 1-benzyl-2-methylimidazole, 4-methyl-2-phenylimidazole, benzimidazole, 2-phenylbenzimidazole; Pyridine, 2-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 4-ethylpyridine, 2-phenylpyridine, 4-phenylpyridine, 2-methyl-4-phenylpyridine, nicotine, nicotinic acid, nicotinamide, In addition to pyridines such as quinoline, 4-hydroxyquinoline, 8-oxyquinoline and acridine; piperazines such as piperazine and 1- (2-hydroxyethyl) piperazine, pyrazine, pyrazole, pyridazine, quinosaline, purine, pyrrolidine, piperidine, 3 Piperidino-1,2-propanediol, morpholine, 4-methylmorpholine, 1,4-dimethylpiperazine, 1,4-diazabicyclo [2.2.2] octane.

  Of the above nitrogen-containing heterocyclic compounds, tertiary amine compounds, amide group-containing compounds, and nitrogen-containing heterocyclic compounds are preferable, and among the amide group-containing compounds, Nt-butoxycarbonyl group-containing amino compounds are preferable, including Among the nitrogen heterocyclic compounds, imidazoles are preferable.

  The acid diffusion control agents can be used alone or in admixture of two or more. The compounding amount of the acid diffusion controller is usually 15 parts by mass or less, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less with respect to 100 parts by mass of the acrylic polymer. In this case, when the compounding amount of the acid diffusion controller exceeds 15 parts by mass, the sensitivity as a resist and the developability of the radiation-irradiated part tend to decrease. If the amount of the acid diffusion controller 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.

  In addition, an alicyclic additive having an acid dissociable group or an alicyclic additive having no acid dissociable group is a component that further improves dry etching resistance, pattern shape, adhesion to a substrate, and the like. It is.

  Examples of such alicyclic additives include 1-adamantanecarboxylic acid t-butyl, 1-adamantanecarboxylic acid t-butoxycarbonylmethyl, 1-adamantanecarboxylic acid α-butyrolactone ester, 1,3-adamantane dicarboxylic acid diester. -T-butyl, 1-adamantane acetate t-butyl, 1-adamantane acetate t-butoxycarbonylmethyl, 1,3-adamantanediacetate di-t-butyl, 2,5-dimethyl-2,5-di (adamantylcarbonyl) Adamantane derivatives such as oxy) hexane; deoxycholate t-butyl, deoxycholate t-butoxycarbonylmethyl, deoxycholate 2-ethoxyethyl, deoxycholate 2-cyclohexyloxyethyl, deoxycholate 3-oxocyclohexyl, Deoxychol Deoxycholic acid esters such as tetrahydropyranyl, deoxycholic acid mevalonolactone ester; lithocholic acid t-butyl, lithocholic acid t-butoxycarbonylmethyl, lithocholic acid 2-ethoxyethyl, lithocholic acid 2-cyclohexyloxyethyl, lithocholic acid Lithocholic acid esters such as 3-oxocyclohexyl, lithocholic acid tetrahydropyranyl, lithocholic acid mevalonolactone ester; dimethyl adipate, diethyl adipate, dipropyl adipate, di-n-butyl adipate, di-t-butyl adipate, etc. And alkyl carboxylic acid esters.

  These alicyclic additives can be used alone or in admixture of two or more. The compounding quantity of an alicyclic additive is 50 mass parts or less normally with respect to 100 mass parts of acrylic polymers, Preferably it is 30 mass parts or less. In this case, when the blending amount of the alicyclic additive exceeds 50 parts by mass, the heat resistance as a resist tends to decrease.

  Further, the surfactant as an additive is a component having an effect of improving coating property, striation, developability and the like. Examples of such surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, and polyethylene glycol dilaurate. In addition to nonionic surfactants such as polyethylene glycol distearate, KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75, no. 95 (manufactured by Kyoeisha Chemical Co., Ltd.), Ftop EF301, EF303, EF352 (manufactured by Tochem Products), Megafax F171, F173 (manufactured by Dainippon Ink and Chemicals), Florard FC430, FC431 (Sumitomo 3M) Asahi Guard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, SC-106 (manufactured by Asahi Glass Co., Ltd.), etc. .

  These surfactants can be used alone or in admixture of two or more. The compounding quantity of surfactant is 2 mass parts or less normally with respect to 100 mass parts of acrylic polymers.

  In addition, the sensitizer as an additive has a function of absorbing radiation energy and transmitting the energy to the photoacid generator, thereby increasing the amount of acid generated. It has the effect of improving the apparent sensitivity of objects. Examples of such sensitizers include carbazoles, benzophenones, rose bengals, anthracenes, phenols and the like. These sensitizers can be used alone or in admixture of two or more. The blending amount of the sensitizer is preferably 50 parts by mass or less with respect to 100 parts by mass of the acrylic polymer.

  Furthermore, examples of additives other than those mentioned above include antihalation agents, adhesion assistants, storage stabilizers, antifoaming agents, and the like.

  The radiation-sensitive resin composition of the present invention is usually dissolved in a solvent so that the total solid content concentration is usually 3 to 50% by mass, preferably 5 to 25% by mass. A composition solution is prepared by filtering through a filter having a pore size of about 0.2 μm.

  Examples of the solvent used in the preparation of the composition solution include linear or branched ketones such as 2-pentanone, 2-hexanone, 2-heptanone, and 2-octanone; cyclopentanone, cyclohexanone, and the like. Cyclic ketones; propylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate; 2-hydroxypropionate alkyls such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate; Alkyl 3-alkoxypropionates such as methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, 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 , Ethyl pyruvate, N-methylpyrrolidone, γ-butyrolactone and the like.

  These solvents may be used alone or in admixture of two or more, but propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 2-heptanone, cyclohexanone, γ-butyrolactone, ethyl 2-hydroxypropionate, 3-ethoxy It is preferable to contain at least one selected from ethyl propionate. However, cyclohexanone is an effective solvent from the viewpoint of solubility, but its use is preferably avoided as much as possible because of its toxicity.

  The radiation sensitive resin composition of the present invention is particularly useful as a chemically amplified resist. In particular, it is useful as a positive resist that can reduce the line edge roughness of a pattern after development.

  In chemically amplified resists, the acid-dissociable groups in the resin are dissociated by the action of the acid generated from the photoacid generator by radiation irradiation to generate carboxyl groups. As a result, an alkali developer in the irradiated area of the resist Thus, the irradiated portion is dissolved and removed by an alkali developer, and a positive resist pattern is obtained.

  When forming a resist pattern from the radiation-sensitive resin composition of the present invention, the composition solution is coated with, for example, a silicon wafer or aluminum by an appropriate application means such as spin coating, cast coating or roll coating. A resist film is formed by coating on a substrate such as a wafer, and in some cases, a heat treatment (hereinafter referred to as “PB”) is performed in advance, and then a predetermined resist pattern is formed on the resist film. Irradiate. Examples of the radiation used at that time include far-field such as ultraviolet rays, KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), F2 excimer laser (wavelength 157 nm), EUV (extreme ultraviolet light, wavelength 13 nm, etc.). A charged particle beam such as an ultraviolet ray and an electron beam, and an X-ray such as synchrotron radiation can be appropriately selected and used. Of these, a far ultraviolet ray and an electron beam are preferable. Moreover, irradiation conditions, such as irradiation amount, are suitably selected according to the compounding composition of a radiation sensitive resin composition, the kind of each additive, etc.

  In the present invention, PEB is preferably performed in order to stably form a high-precision fine pattern. By this PEB, the dissociation reaction of the acid dissociable organic group in the acrylic polymer proceeds smoothly. The heating condition of PEB varies depending on the composition of the radiation sensitive resin composition, but is usually 30 to 200 ° C, preferably 50 to 170 ° C.

  In the present invention, in order to maximize the potential of the radiation-sensitive resin composition, for example, as disclosed in Japanese Patent Publication No. 6-12458, an organic or inorganic substrate is used. An antireflection film can also be formed, and in order to prevent the influence of basic impurities contained in the environmental atmosphere, as disclosed in, for example, JP-A-5-188598, A protective film can be provided on the substrate, or these techniques can be used in combination.

  Next, the irradiated resist film is developed using an alkali developer to form a predetermined resist pattern. As the alkaline developer, for example, an alkaline aqueous solution in which tetramethylammonium hydroxide is dissolved is preferable. The concentration of the alkaline aqueous solution is usually 10% by mass or less. In this case, if the concentration of the alkaline aqueous solution exceeds 10% by mass, the non-irradiated part may be dissolved in the developer, which is not preferable. In addition, an appropriate amount of a surfactant or the like can be added to the alkaline aqueous solution. In addition, after developing with an alkali developing solution, it is generally washed with water and dried.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Here, the part is based on mass unless otherwise specified.

Each measurement and evaluation in Examples and Comparative Examples was performed as follows. Mw and Mn are GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) manufactured by Tosoh Corporation, using a monodisperse polystyrene as the standard under the analysis conditions of a flow rate of 1.0 ml / min, an elution solvent tetrahydrofuran, and a column temperature of 40 ° C. Measured by gel permeation chromatography (GPC). Further, ¹ H- and ¹³ C-NMR analysis of each polymer was performed using “JNM-EX270” manufactured by JEOL Ltd. and using CDCl ₃ as a measurement solvent.

sensitivity:
Using a silicon wafer having an ARC29A film (made by Brewer Science) having a film thickness of 770 mm on the surface as a substrate, the composition solution was applied onto the substrate by spin coating, and the conditions shown in Table 1 were used. A resist film having a thickness of 0.15 μm formed by PB was exposed through a mask pattern using a full-field reduction projection exposure apparatus S306C (numerical aperture 0.75) manufactured by Nikon. Then, after performing PEB under the conditions shown in Table 1, it was developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 30 seconds, washed with water, and dried to form a positive resist pattern. Formed. At this time, the exposure amount for forming a hole-and-space pattern (1H1S) having a diameter of 0.10 μm with a one-to-one line width was defined as the optimum exposure amount, and this optimum exposure amount was defined as the sensitivity.

Isolated Hall DOF:
With respect to Examples 1 to 7 and Comparative Example 1, an isolated hole mask having an arbitrary size in which the diameter of the isolated hole formed by the “sensitivity” is 100 nm is found, and the diameter of the isolated hole at that time is 100 nm ± The depth of focus range of 10% was measured.

Pattern shape:
The lower side dimension Lb and the upper side dimension La of the square cross section of the hole pattern (1H1S) with a hole width of 0.10 μm are measured with a scanning electron microscope, 0.85 ≦ La / Lb ≦ 1 is satisfied, and the pattern shape is When the skirt was not drawn, the pattern shape was “good”, and when 0.85> La / Lb, the pattern shape was “bad”.

(Synthesis Example 1)
40.97 g (50 mol%) of the compound (compound a) in which R ¹ : —CH ₃ and n ¹ = 4 in the general formula (1), norbornene lactone methacrylate represented by the general formula (2) (compound b) A monomer solution was prepared by dissolving 59.03 g (50 mol%) and 4.36 g of dimethyl azobisisobutyrate in 250 g of 2-butanone. Further, the inside of a 1000 ml three-necked flask charged with 100 g of 2-butanone was heated to 80 ° C. while stirring, and the monomer solution was added dropwise at a rate of 12 ml / 5 minutes using a dropping funnel. The polymerization was carried out at 80 ° C. for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the reaction solution was cooled to 30 ° C. or lower, and poured into 2,250 g of a 1: 1 mixed solvent of hexane and 2-propanol, and the precipitated white powder was filtered off. Thereafter, the operation of mixing the white powder with 450 g of a 1: 1 mixed solvent of hexane and 2-propanol as a slurry and washing the mixture twice was washed, filtered, dried at 50 ° C. for 17 hours, A powdery resin (78 g, yield 78% by mass) was obtained.

This resin had Mw of 7,800 and Mw / Mn = 1.5, and the measured values of ¹ H-NMR were as follows. ¹ H-NMR (400 MHz, solvent CDCl ₃ , internal standard TMS): δ (ppm) = 0.82 to 2.30 (m), 2.56 (brs), 3.24 (brs), 4.54 ( brs). Further, from ¹³ C-NMR analysis, the content of the repeating unit (1) (where R ¹ : —CH ₃ , n ¹ = 4) and the repeating unit (2) was 45.6: 54.4 (mol%). ). This resin is referred to as “resin (A-1)”.

(Synthesis Example 2)
21.54 g (50 mol%) of the compound (compound c) in which R ¹ : —CH ₂ CH ₃ , n = 4 in the general formula (1), norbornene lactone methacrylate (compound b) represented by the general formula (2) ) And 28.46 g (50 mol%) and 2.10 g of dimethyl azobisisobutyrate were dissolved in 125 g of 2-butanone to prepare a monomer solution. In addition, the inside of a 500 ml three-necked flask charged with 50 g of 2-butanone was heated to 80 ° C. while stirring, and the monomer solution was dropped at a rate of 5 ml / 5 minutes using a dropping funnel. The polymerization was carried out at 80 ° C. for 6 hours with the start of dropping as the polymerization start time. After the completion of the polymerization, the reaction solution was cooled to 30 ° C. or lower and poured into 1,125 g of a 1: 1 mixed solvent of hexane and 2-propanol, and the precipitated white powder was filtered off. Thereafter, the operation of mixing the white powder with 225 g of a 1: 1 mixed solvent of hexane and 2-propanol as a slurry and stirring was repeated twice, washed, filtered, and dried at 50 ° C. for 17 hours. A powdery resin (78 g, yield 78% by mass) was obtained.

This resin had Mw of 7,000 and Mw / Mn = 1.5, and the measured values of ¹ H-NMR were as follows. ¹ H-NMR (400 MHz, solvent CDCl ₃ , internal standard TMS): δ (ppm) = 0.81 to 2.34 (m), 2.57 (brs), 3.24 (brs), 4.56 ( brs). ^{From 13} C-NMR analysis, the content of repeating unit (1) (provided that R ¹ : —CH ₂ CH ₃ , n ¹ = 4) and repeating unit (2) was 46.4: 53.6 (mol%). ). This resin is referred to as “resin (A-2)”.

(Synthesis Example 3)
10.05 g (25 mol%) of compound a, 28.99 g (50 mol%) of compound b, 10 compounds (compound d) in the general formula (3) where R ² : —CH ₃ and n ² = 4 A monomer solution was prepared by dissolving .97 g (25 mol%) and 2.14 g of dimethyl azobisisobutyrate in 100 g of 2-butanone to obtain a homogeneous solution. In addition, the inside of a 500 ml three-necked flask charged with 50 g of 2-butanone was heated to 80 ° C. while stirring, and the monomer solution was dropped at a rate of 5 ml / 5 minutes using a dropping funnel. The polymerization was carried out at 80 ° C. for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the reaction solution was cooled to 30 ° C. or lower, poured into 1000 g of methanol, and the precipitated white powder was separated by filtration. Thereafter, the operation of mixing the white powder with 200 g of methanol and stirring it as a slurry was repeated twice, washed, filtered and dried at 50 ° C. for 17 hours to obtain a white powder resin (39 g, yield 78 mass). %).

This resin had Mw of 8,700 and Mw / Mn = 1.6, and the measured values of ¹ H-NMR were as follows. ¹ H-NMR (400 MHz, solvent CDCl ₃ , internal standard TMS): δ (ppm) = 0.82 to 2.30 (m), 2.57 (brs), 3.25 (brs), 4.41 to 4.72 (m). ^{From 13} C-NMR analysis, repeating unit (1) (provided that R ¹ : —CH ₃ , n ¹ = 4), repeating unit (2) and repeating unit (3) (provided that R ² : —CH ₃ , n ² = 4) was a copolymer having a content of 21.9: 58.1: 20.0 (mol%). This resin is referred to as “resin (A-3)”.

(Synthesis Example 4)
Compound c is 10.58 g (25 mol%), compound b is 27.96 g (50 mol%), and R ² : —CH ₂ CH ₃ , n ² = 4 in the general formula (3) (compound e) A white powder resin in the same manner as in Synthesis Example 3 except that 11.46 g (25 mol%) and 2.07 g of dimethyl azobisisobutyrate were dissolved in 100 g of 2-butanone to prepare a monomer solution. (35 g, yield 70 mass%) was obtained.

This resin had Mw of 8,600 and Mw / Mn = 1.6, and the measured values of ¹ H-NMR were as follows. ¹ H-NMR (400 MHz, solvent CDCl ₃ , internal standard TMS): δ (ppm) = 0.82 to 2.30 (m), 2.57 (brs), 3.24 (brs), 4.38 to 4.74 (m). ^{From 13} C-NMR analysis, repeating unit (1) (provided that R ¹ : —CH ₂ CH ₃ , n ¹ = 4), repeating unit (2) and repeating unit (3) (provided that R ² : —CH ₂ It was a copolymer having a content of CH ₃ , n ² = 4) of 22.5: 56.5: 21.0 (mol%). This resin is referred to as “resin (A-4)”.

(Synthesis Example 5 (for comparison))
Other than using a monomer solution in which 56.92 g (50 mol%) of compound b, 43.08 g (50 mol%) of compound c and 4.21 g of dimethyl azobisisobutyrate were dissolved in 200 g of 2-butanone to form a homogeneous solution. Obtained a white powder resin in the same manner as in Synthesis Example 2 (73 g, yield 73 mass%).

This resin had Mw of 6,200 and Mw / Mn = 1.5, and the measured values of ¹ H-NMR were as follows. ¹ H-NMR (400 MHz, solvent CDCl ₃ , internal standard TMS): δ (ppm) = 0.78-2.30 (m), 2.58 (brs), 3.25 (brs), 4.40- 4.71 (m). ^{From 13} C-NMR analysis, the content of the repeating unit (3) (provided that R ² : —CH ₃ , n ² = 4) and the repeating unit represented by the formula (2) was 45.5: 54.5 ( Mol%) copolymer. This resin is referred to as “resin (R-1)”.

Examples 1-7 and Comparative Example 1
Various evaluations were performed on each composition composed of the components shown in Table 2. The evaluation results are shown in Table 3. In Table 2, components other than the resins (A-1) to (A-4) and (R-1) are as follows.

[Photoacid generator (B)]
B-1: 1- (4-n-Butoxynaphthyl) tetrahydrothiophenium nonafluoro-n-butanesulfonate Formula (6)

  B-2: Triphenylsulfonium nonafluoro-n-butanesulfonate Formula (7)

[Acid diffusion controller (D)]
D-1: 3-piperidino-1,2-propanediol Formula (8)
D-2: Nt-butoxycarbonyl-4-hydroxypiperidine Formula (9)

[Alicyclic compound (E)]
E-1: t-butoxycarbonylmethyl lithocholic acid formula (10)

[Solvent (C)]
C-1: Propylene glycol monomethyl ether acetate C-2: Cyclohexanone

  The radiation sensitive resin composition of this invention can be used for manufacture of an integrated circuit element.

Claims (4)

Polystyrene by gel permeation chromatography (GPC) containing the repeating unit represented by the following general formula (1) and the repeating unit represented by the following general formula (2) in excess of 90 mol% with respect to all the repeating units. A nitrogen-free copolymer having a converted weight average molecular weight of 1,000 to 100,000.

(In Formula (1), R ¹ represents a linear or branched alkyl group having 1 to 3 carbon atoms, and n ¹ represents an integer of 1 to 5.) A copolymer containing repeating units represented by the following general formulas (1), (2) and (3) and having a polystyrene-reduced weight average molecular weight of 1,000 to 100,000 by gel permeation chromatography (GPC).

(In the formulas (1) and (3), R ¹ and R ² each represent a linear or branched alkyl group having 1 to 3 carbon atoms, and n ¹ and n ² each represent an integer of 1 to 5 To express.)   The copolymer according to claim 1 or 2, wherein the repeating unit represented by the general formula (1) is 10 to 60 mol% with respect to all repeating units.   The radiation sensitive resin composition containing the copolymer as described in any one of Claims 1-3, a photo-acid generator, and a solvent.