JPH11352695A - Positive type resist composition using narrowly dispersible polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chemical amplification type positive type resist compsn. excellent in resolution by using a resin having a narrow mol.wt. distribution prepd. by a certain method. SOLUTION: An alkali-insoluble or hardly alkali-soluble resin (A) which is made alkali-soluble by the action of an acid and an acid generating agent (B) are dissolved in an org. solvent (C) to obtain the objective chemical amplification type positive type resist compsn. The resin A is prepd. by subjecting a styrene deriv. represented by formula (I) (where R is 1-12C alkyl or 1-12C alkanoyl) to living radical polymn. in the presence of a free radical initiator and a stable free redical working agent, releasing at least part of groups corresponding to -R of the resultant narrowly dispersible polystyrene to convert the corresponding -O-R parts into hydroxyl groups and partially protecting the hydroxyl groups with acid labile groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a chemically amplified positive-acting resist composition containing a resin component and an acid generator. More specifically, the present invention relates to improvement of a resin component of such a resist composition.

[0002]

2. Description of the Related Art In recent years, with the increase in the degree of integration of integrated circuits, the formation of quarter-micron patterns has been required. For such demands, 64M DRAM and 256M
Excimer laser lithography, which enables the manufacture of DRAM, has attracted attention. As a resist suitable for the excimer laser lithography process, a so-called chemically amplified resist utilizing an acid catalyst and a chemical amplification effect is being used. Chemically-amplified resist changes the solubility of an irradiated part in an alkaline developer by a reaction using an acid generated from an acid generator in a part irradiated with radiation, thereby forming a positive or negative pattern. give.

As described above, the chemically amplified resist is used for the purpose of forming a fine pattern, but further miniaturization is required. In order to increase the resolution of the resist material so that a finer pattern can be formed,
It is effective to narrow the molecular weight distribution of the resin used, that is, to reduce the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), to obtain a narrow dispersibility. It is known that there is. Styrene derivatives have attracted attention as a polymer whose molecular weight can be controlled relatively easily. Among them, poly (hydroxystyrene) -based resins have excellent development resistance and plasma resistance. It has been attracting attention and being studied.

In order to narrow the molecular weight distribution of the poly (hydroxystyrene) resin used for the resist material, a method using anionic polymerization, for example, a method using anionic living polymerization as described in JP-A-6-32839 is used. Are known. However, the anionic polymerization method requires severe conditions such as requiring an oxygen atmosphere and the absence of moisture, and requiring a dangerous initiator for handling such as an organometallic compound, and the production cost is low. It is disadvantageous compared to polymerization.

On the other hand, JP-A-6-199916 discloses that a free radical initiator and a stable free radical activator are mixed with a polymerizable monomer compound and heated at 100 to 160 ° C. to form a styrene-based compound having a narrow molecular weight distribution. Free radical polymerization methods for obtaining polymers have been proposed. In this method, the stable free radical agent is reversibly added to the growth terminal of the polymer to protect the growth terminal, and the polymerization proceeds while maintaining the living property.

[0006]

Under such circumstances,
An object of the present invention is to provide a chemically amplified positive resist composition having excellent resolution by using a resin having a narrow molecular weight distribution produced by a certain method.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention. That is, the present invention provides a chemically amplified positive resist composition essentially containing the following three components.

(A) The following formula (I)

[0009]

Wherein R represents alkyl having 1 to 12 carbon atoms or alkanoyl having 1 to 12 carbon atoms in total, in the presence of a free radical initiator and a stable free radical activator. After removing at least a part of the group corresponding to -R of the narrowly dispersible polystyrene obtained by radical polymerization in a living manner and converting the corresponding -OR part to a hydroxyl group, it is immiscible with acid. A resin which partially protects the hydroxyl group with a stable group and which itself is insoluble or hardly soluble in alkali, but becomes alkali-soluble by the action of an acid, (B) an acid generator, and (C) Organic solvents that dissolve these.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, manufactured by a specific method, with a narrow dispersibility,
In addition, a poly (p-hydroxystyrene) resin in which a part of hydroxyl groups is protected by an acid-labile group is used. In producing this resin, a styrene derivative represented by the above formula (I) is used as a monomer. In the formula (I), R is alkyl having 1 to 12 carbon atoms or alkanoyl having 1 to 12 carbon atoms. The alkyl represented by R may be linear or branched when it has 3 or more carbon atoms.
Advantageously, it is also a branched alkyl, especially an alkyl linked at a quaternary carbon to an oxygen atom in the formula. Suitable alkyls include isopropyl, sec-butyl, tert-butyl, tert-amyl, tert-octyl and the like. The alkanoyl represented by R may also be linear or branched when the total number of carbon atoms is 4 or more. Specific alkanoyl includes acetyl, propanoyl and the like. Among them, R is preferably tert-butyl.

The styrene derivative of formula (I) is polymerized in the presence of a free radical initiator and a stable free radical agent. The free radical initiator used here may be any compound that decomposes to generate free radicals, and specifically, benzoyl peroxide, tert-
Peroxides such as -butyl hydroperoxide and di-tert-butyl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile and dimethyl 2,2'-azobisisobutyrate can be used.

[0013] Stable free radical acting agents used in combination with a free radical initiator are compounds that are stably present in the form of free radicals. Such free radicals that are stably present include those having a nitrogen atom at or near the radical portion, specifically, those that have become radicals at the nitrogen atom portion or other atom portions bonded to the nitrogen atom. Radicals, more specifically, hydrazinyl radicals and nitroxide radicals each corresponding to the following formula:

[0014]

For example, 2,2,6,6-tetramethyl-
1-piperidinyloxy (commercial product name "TEMPO"), 4-
Amino-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,
2,6,6-tetramethyl-1-piperidinyloxy,
Nitroxides such as 4,4-dimethyl-1,3-oxazolin-3-yloxy, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, phenyl tert-butyl nitroxide and di-tert-butyl nitroxide And 2,2-di (4-tert-octylphenyl) -1
-Picrylhydrazyl and the like can be used as stable free radical agents.

In polymerizing the styrene derivative of the formula (I), it is preferable to use the styrene derivative in such a manner that the molar ratio of the stable free radical acting agent / free radical initiator is in the range of 0.7 to 2.0. Having a molar ratio of 1.0 to 1.0.
It is more preferable to set the range to 5.

To produce the resin used in the present invention, first,
The styrene derivative of formula (I) is polymerized in the presence of a free radical initiator and a stable free radical agent as described above. Thus, by the presence of the free radical initiator and the stable free radical agent, the free radical initiator is first added to the styrene derivative of the formula (I) to form a growing chain, and the stable free radical agent is further added thereto. Addition, the chain is temporarily but reversibly terminated, and the growth of the chain proceeds when the added stable free radical agent is eliminated again. become. This polymerization can be performed by various known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. The polymerization temperature is generally selected from the range of about 100 to 180 ° C, preferably about 110 to 140 ° C. The reaction time varies depending on the desired degree of polymerization or molecular weight, but is generally about 5 to 50 hours. When the styrene derivative of the formula (I) is a liquid, for example, p-tert
In the case of butoxystyrene, if bulk polymerization is performed using the same, the polymer after the reaction can be obtained in a state of being dissolved in the styrene derivative as the raw material.

By conducting radical polymerization in a living manner, a polymer having a narrow molecular weight distribution (narrow dispersibility) can be obtained by a simple operation. The polydispersity (Mw / Mn) of the resulting polymer is usually in the range of 1.1 to 1.5. By selecting the conditions of the polymerization reaction, for example by adjusting the molar ratio of the free radical initiator to the styrene derivative of formula (I), the molecular weight of the resulting polymer can be controlled appropriately. Usually, a polymer having a weight average molecular weight (Mw) in the range of about 3,000 to 100,000 is obtained.

Next, part or all of the group corresponding to -R in the above formula (I) is eliminated from the styrene polymer thus obtained. This operation can be performed according to a known method, for example, the method described in JP-A-6-32839. Specifically, after dissolving the styrene-based polymer in a suitable solvent, the mixture is treated with an acid to remove a group corresponding to -R in the formula (I) from the polymer, The corresponding -OR moiety can be a hydroxyl group. As the solvent, for example, 2-propanol, dioxane, acetone, acetonitrile, toluene and the like are used alone or in combination of two or more. Any solvent that is miscible with water can be used in the form of a mixed solvent with water. As the acid, for example, hydrochloric acid, hydrobromic acid, p-toluenesulfonic acid and the like are used.

Here, even when a group corresponding to -OR in the formula (I) is partially left, the unit containing this group is preferably not more than 30 mol% of the whole polymer. From the viewpoint of resist performance, particularly when R is tert-butyl, it is preferable that p-tert-butoxystyrene units remain in the range of 5 to 20 mol% of the entire polymer. The residual ratio of the group corresponding to -OR can be adjusted by controlling the time of the elimination reaction. That is,
In the above elimination reaction, -OR
Is determined by nuclear magnetic resonance (NMR) measurement, and the residual ratio of the group corresponding to -OR is plotted with respect to the reaction time, and the ratio of the group corresponding to -OR is determined as the target. By estimating the reaction time until the value is reached, and terminating the elimination reaction when the time is reached, it is possible to obtain a polymer in which the group corresponding to -OR remains at a desired ratio. .

In this way, a poly (hydroxystyrene) having a narrow molecular weight distribution or a polymer in which a part of the hydroxyl groups of the poly (hydroxystyrene) is alkyletherified or alkanoic acid ester is obtained. Is further partially protected with acid labile groups. The resin which is the main component of the chemically amplified positive resist composition is insoluble or hardly soluble in alkali by itself, but undergoes a chemical change by the action of an acid to become alkali-soluble. A part of the phenolic hydroxyl group of the polymer obtained by the above living radical polymerization and subsequent elimination reaction is protected from dissolution in an alkali developing solution and protected by an acid-labile group. By doing so, a resin having such a function is obtained.

The group introduced here, which has the ability to inhibit dissolution in an alkali developing solution but is unstable to an acid, can be any of various known protecting groups. For example, tert-butoxycarbonyl, tert-butoxycarbonylmethyl, 1-ethoxyethyl, 1-methoxyethyl, 1-propoxyethyl, 1-isopropoxyethyl, 1-tert-
Butoxyethyl, 1-isobutoxyethyl, 1-butoxyethyl, 1-pentyloxyethyl group, 1-cyclopentyloxyethyl, 1-hexyloxyethyl, 1-cyclohexyloxyethyl, 1-heptyloxyethyl, 1-cyclo Heptyloxyethyl, 1-methoxypropyl, 1-
1-alkoxyalkyl groups such as methoxy-1-methylethyl, tetrahydro-2-pyranyl, 6-methoxytetrahydro-2-pyranyl, 6-ethoxytetrahydro-2-pyranyl, tetrahydro-2-furyl, 5-methoxytetrahydro- Examples thereof include 2-residues of cyclic saturated ethers such as 2-furyl and 5-ethoxytetrahydro-2-furyl, and these groups are substituted with hydrogen of a phenolic hydroxyl group. Among these protecting groups, a group forming a so-called acetal-type bond with an oxygen atom of a phenolic hydroxyl group, that is, a 2-residue of a 1-alkoxyalkyl group or a cyclic saturated ether is preferably a 1-alkoxyalkyl group. Groups are preferred.

Such an acid labile group is introduced by a known protecting group introduction reaction. For example, di-tert dicarbonate
-Hydrogen in the hydroxyl group by reacting
tert-butoxycarbonyl,
By reacting tert-butyl chloroacetate, hydrogen in the hydroxyl group can be replaced with tert-butoxycarbonylmethyl. Also, the following formula (II)

[0024]

(Wherein R ¹ is hydrogen or a group having 1 to 4 carbon atoms)
R ² represents alkyl having 1 to 6 carbon atoms or cycloalkyl having 5 to 7 carbon atoms;
³ and R ⁴ are independently hydrogen or 1 to carbon atoms
R ² represents an alkyl group, or R ² and R ³ together form an alkylene chain, which alkylene chain may be substituted by alkoxy having 1 to 4 carbon atoms). By reacting the compound, hydrogen in the hydroxyl group can be replaced by a 1-alkoxyalkyl group or a 2-residue of a cyclic saturated ether.

In introducing these protective groups into the phenolic hydroxyl groups of the resin, the ratio of the hydroxyl groups substituted with the protective groups (protective group introduction rate) is determined by comparing the ratio of the hydroxyl groups before the protective group introduction to the hydroxyl groups. In general, 10 to 10
It is preferable to set it in the range of 50%. That is, it is preferable that the p-hydroxystyrene unit protected by the acid-labile group is present in the range of 10 to 50 mol% of the whole resin.

By starting from the styrene derivative of the formula (I) and subjecting it to a living radical polymerization reaction, an elimination reaction and another protecting group introduction reaction, it is suitable as a resin component of a chemically amplified positive resist. A narrowly dispersible poly (p-hydroxystyrene) -based resin is obtained. Since the degree of polymerization of the polymer is hardly changed by the elimination reaction and the subsequent protective group introduction reaction, the polydispersity (Mw / Mn) of this resin is generally in the range of 1.0 to 1.5. And a weight average molecular weight (Mw) of about 2,000 to 100,
000 range. In the positive resist composition of the present invention, the narrow-dispersion poly (p-hydroxystyrene) -based resin obtained as described above is used as the resin component, but this resin component impairs the effects of the present invention. Other resins may be included as long as they do not exist.

The resist composition contains an acid generator. The acid generator as used herein means that an acid is generated by irradiating a substance itself or a resist composition containing the substance with radiation. It is a compound that is generated. Of course 2
It can also be used as a mixture of more than one compound. Examples include onium salts, organic halogen compounds, compounds having a diazomethane disulfonyl skeleton, disulfone compounds, orthoquinonediazide compounds, sulfonic acid compounds, and the like. In the present invention, a compound having a diazomethane disulfonyl skeleton, a disulfone compound, a sulfonic acid compound and the like are preferably used as the acid generator. Examples of the sulfonic acid compound serving as an acid generator include alkyl sulfonic acid esters, haloalkyl sulfonic acid esters, aryl sulfonic acid esters, camphor sulfonic acid esters, and the like. The alcohol components constituting these esters include pyrogallol, 2- or 4-nitrobenzyl alcohol, 2,6-dinitrobenzyl alcohol,
-Hydroxyimide compounds, oxime compounds and the like.

Compounds having a diazomethane disulfonyl skeleton include, for example, bis (cyclohexylsulfonyl)
Examples include diazomethane, bis (phenylsulfonyl) diazomethane, bis (p-tolylsulfonyl) diazomethane, bis (2,4-xylylsulfonyl) diazomethane and the like. Disulfone compounds include, for example, diphenyl disulfone, di-p-tolyl disulfone, phenyl p-tolyl disulfone, phenyl p-methoxyphenyl disulfone, and the like. Examples of the sulfonic acid compound include N- (phenylsulfonyloxy) succinimide, N- (methylsulfonyloxy) succinimide, N- (trifluoromethylsulfonyloxy) succinimide, N- (butylsulfonyloxy) succinimide, and N- (butylsulfonyloxy) succinimide. (10-camphorsulfonyloxy) succinimide, N- (trifluoromethylsulfonyloxy) phthalimide, N- (trifluoromethylsulfonyloxy) naphthalimide, 2-nitrobenzyl p-toluenesulfonate, 4-nitrobenzyl p-toluenesulfonate, 2,6-dinitrobenzyl p-toluenesulfonate, 1,2,3-
Benzenetriyl trismethanesulfonate, 1-benzoyl-1-phenylmethyl p-toluenesulfonate (commonly called benzoin tosylate), 2-benzoyl-
2-hydroxy-2-phenylethyl p-toluenesulfonate (commonly called α-methylol benzoin tosylate), α- (p-tolylsulfonyloxyimino) -4
-Methoxyphenylacetonitrile and the like.

In general, it is known that, in a chemically amplified positive resist, the performance degradation due to acid deactivation due to withdrawal after exposure can be improved by adding an organic base compound as a quencher. In the present invention, it is preferable to blend such an organic base compound.

Specific examples of the organic base compound used herein include hexylamine, heptylamine, octylamine, nonylamine, decylamine, aniline, 2-, 3-
-Or 4-methylaniline, 4-nitroaniline, 1-
Primary amines such as naphthylamine and 2-naphthylamine; secondary amines such as dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, N-methylaniline, piperidine and diphenylamine;
Triethylamine, trimethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine , Methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine , Tris [2- (2-methoxyethoxy) ethyl] amine,
Tertiary amines such as triisopropanolamine and N, N-dimethylaniline; quaternary ammonium salts such as tetrabutylammonium hydroxide; diamines such as ethylenediamine, tetramethylenediamine and hexamethylenediamine; imidazole, pyridine;
Examples include unsaturated cyclic amines such as 4-methylpyridine, 4-methylimidazole and bipyridine.

These organic base compounds can be used alone or in combination of two or more. In the present invention, it is particularly preferable to use a tertiary amine and / or a quaternary ammonium salt. In addition, among the organic base compounds, even after the pre-baking of the resist film formed on the substrate, it remains in the resist film to exhibit the effect.
One that does not evaporate at the temperature of pre-bake, specifically 150
Those having a boiling point of not lower than ° C are preferred.

The preferred composition ratio of the positive resist composition is such that the resin component is in the range of 50 to 98% by weight, more preferably 75 to 98% by weight, based on the total solid content in the composition. Is in the range of 0.05 to 20% by weight. When an organic base compound is blended, it is preferably used in the range of 0.001 to 10% by weight. The resist composition of the present invention may further contain, if necessary, various additives commonly used in this field, such as a dissolution inhibitor, a sensitizer, a dye, an adhesion improver, and a water retention agent. . In order to generate an acid in a chemically amplified resist, the presence of water is required. However, the presence of a small amount of a water retention agent such as polypropylene glycol allows the acid to be generated efficiently. When these additives are used, their amounts total up to about 20% by weight, based on the total solids weight in the composition.

The positive resist composition of the present invention is obtained by mixing and dissolving each of the above components in an organic solvent. On this occasion,
Usually, an organic solvent is used so that the total solid concentration is 10 to 50% by weight. The organic solvent may be any one that dissolves the above-mentioned components, and may be any of those commonly used in this field. For example, glycol ether esters such as ethyl cellosolve acetate, methyl cellosolve acetate, propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate, ethyl cellosolve, methyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether and diethylene glycol dimethyl ether. Glycol mono- or diethers, such as ethyl lactate, butyl acetate and ethyl pyruvate, 2-heptanone,
Examples thereof include ketones such as cyclohexanone and methyl isobutyl ketone, and aromatic hydrocarbons such as xylene. These solvents can be used alone or in combination of two or more.

This positive resist composition is applied on a substrate such as a silicon wafer to form a resist film. Thereafter, usually, pre-baking, patterning exposure, and diffusion of an acid generated in an exposed portion are performed to remove a protective group of the resin. The pattern is formed through the steps of post-exposure baking for separating and regenerating the acid and development with an alkali developer.

[0036]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, percentages and parts representing the content or the used amount are based on weight unless otherwise specified.

Synthesis Example 1 (1a) Polymerization of p-tert-butoxystyrene 880 g of p-tert-butoxystyrene, 4.03 g of benzoyl peroxide and 2,2,6,6-tetramethyl-1-piperidinyloxy 3 .38g was charged to the reactor,
After purging with nitrogen, the polymerization reaction was continued at 130 ° C. for 8 hours. Thereafter, the solution was poured into methanol to precipitate the product, which was separated and dried to isolate 283.2 g of a polymer. The molecular weight and distribution of the obtained polymer were determined by gel permeation chromatography (GPC) using polystyrene as a standard. The weight average molecular weight was about 25,000 and the polydispersity was 1.20. Was.

(1b) Elimination of tert-butyl group After dissolving 282 g of the polymer obtained in the above (1a) in 1410 g of 2-propanol, a small amount of concentrated hydrochloric acid was added at 65 ° C., and the mixture was stirred for 5 hours. The solution was then poured into water to precipitate the product and separate. The obtained crude crystals were dissolved in ethyl acetate, ion-exchanged water was added thereto, and the mixture was separated and washed. After distilling off the solvent and concentrating, acetone was added, the solution was poured into ion-exchanged water to precipitate the product, separated and dried to obtain a poly (p) partially containing tert-butoxy group.
-Hydroxystyrene) 207 g were obtained. This resin te
When the rt-butoxylation ratio was determined by NMR measurement, p
-Tert-butoxystyrene unit is 10 mol%, and the remainder is p
-Hydroxystyrene units.

(1c) 1-ethoxyethylation 97 g of the resin obtained in the above (1b) and 0.22 g of p-toluenesulfonic acid monohydrate were dissolved in 650 g of propylene glycol monomethyl ether acetate, and 20 g of ethyl vinyl ether was added thereto. Was added dropwise. After stirring at 25 ° C. for 3 hours,
Methyl isobutyl ketone and ion-exchanged water were added for liquid separation. The obtained organic layer was mixed with ion-exchanged water and subjected to liquid separation three times, and washed. After the solvent was distilled off from the organic layer and concentrated, propylene glycol monomethyl acetate was added and the solvent was further distilled off to replace the solvent, thereby obtaining 330 g of a resin solution.

The solid content concentration of this resin solution was determined by a heating weight loss method and found to be 27%. The 1-ethoxyethylation ratio (the ratio of 1-ethoxyethoxy groups to the total of hydroxyl groups, p-tert-butoxy groups and 1-ethoxyethoxy groups) in the resin was 33% as determined by NMR measurement. . Therefore, this resin is p-te
It is composed of 10 mol% of rt-butoxystyrene units, 33 mol% of p-1-ethoxyethoxystyrene units, and the remainder composed of p-hydroxystyrene units. The resin has a weight average molecular weight of about 21,000 and a polydispersity of 1.
20.

Synthesis Example 2 (for comparison) (2a) Polymerization of p-tert-butoxystyrene 221 g of p-tert-butoxystyrene was dissolved in 219 g of 2-propanol, and the temperature was raised to 75 ° C. by purging with nitrogen. To this, 8.3 g of dimethyl 2,2'-azobisisobutyrate dissolved in 34.6 g of 2-propanol was added dropwise.
Further, the polymerization reaction was continued at the same temperature for 5 hours. Thereafter, the solution was poured into methanol to precipitate a product, separated and dried to isolate 210 g of a polymer. When the molecular weight and the distribution of the obtained polymer were determined by the same method as in (1a) of Synthesis Example 1, the weight average molecular weight was about 20,000,
The polydispersity was 1.8.

(2b) Elimination of tert-butyl group After dissolving 105 g of the polymer obtained in the above (2a) in 534 g of 2-propanol, a small amount of concentrated hydrochloric acid was added at 70 ° C., followed by stirring for 3 hours. . Then cool to 55 ° C and add 3 more
After stirring for an hour, methyl acetate and ion-exchanged water were added to carry out liquid separation. The lower layer was poured into water, and the obtained crude crystals were dissolved in ethyl acetate, and ion-exchanged water was added for liquid separation and washing. After evaporating the solvent and concentrating, acetone is added, and the solution is poured into ion-exchanged water to precipitate the product, separated,
By drying, 60 g of poly (p-hydroxystyrene) partially having tert-butoxy groups remaining was obtained. When the tert-butoxylation ratio of this resin was determined by NMR measurement, it was found that p-tert-butoxystyrene units were 10 mol% and the rest were p-hydroxystyrene units.

(2c) 1-ethoxyethylation 60 g of the resin obtained in the above (2b) and 0.063 g of p-toluenesulfonic acid monohydrate were mixed with methyl isobutyl ketone 36.
0 g, and 12.5 g of ethyl vinyl ether
Was added dropwise. After stirring at 25 ° C. for 3 hours, ion-exchanged water was added to carry out liquid separation. The obtained organic layer was mixed with ion-exchanged water and subjected to liquid separation three times, and washed. After the solvent was distilled off from the organic layer and concentrated, propylene glycol monomethyl acetate was added, and the solvent was further distilled off to replace the solvent, thereby obtaining 193 g of a resin solution.

The solid content concentration of this resin solution was 35% as determined by a heating weight loss method. Further, the 1-ethoxyethylation ratio in the resin was determined by the same method as in (1c) of Synthesis Example 1, and it was 33%. Therefore, this resin contains 10 mol% of p-tert-butoxystyrene unit,
-1-ethoxyethoxystyrene unit is composed of 33 mol%, and the rest is composed of p-hydroxystyrene unit.
The resin has a weight average molecular weight of about 17,000 and a polydispersity of 1.8.

Examples and Comparative Examples The following components were mixed and dissolved, and filtered with a fluororesin filter to obtain a resist solution.

Resin component: Resin obtained in (1c) of Synthesis Example 1 (Example) or resin obtained in (2c) of Synthesis Example 2 (Comparative Example) (solid content) 13.5 parts Acid generator: bis (cyclohexyl) Sulfonyl) diazomethane 0.5 parts Quencher: Tris [2- (2-methoxyethoxy) ethyl] amine 0.01 parts Tetrabutylammonium hydroxide 0.01 parts Water retention agent: Polypropylene glycol 0.135 parts (Mw 1,000, manufactured by Wako Pure Chemical Industries, Ltd.) Solvent ： 80 parts of propylene glycol monomethyl ether acetate (including the amount brought in from the resin solution)

On a silicon wafer cleaned by a conventional method,
Spin-coat the above resist solution using a spin coater,
Next, the silicon wafer is placed on a hot plate for 90 minutes.
Pre-baking was performed at 90 ° C. for 90 seconds to form a resist film having a thickness of 0.50 μm. The coated film after the pre-baking is exposed through a chrome mask having a pattern to a K film having an exposure wavelength of
Exposure was performed using an rF excimer laser stepper (“NSR-2205 EX12B” manufactured by Nikon Corporation, NA = 0.55, σ = 0.8) while changing the exposure stepwise. The exposed wafer was heated on a hot plate at 100 ° C. for 90 seconds. This was developed with a 2.38% aqueous solution of tetramethylammonium hydroxide to obtain a positive pattern.

Each positive pattern was evaluated as follows, and the results are shown in Table 1.

Sensitivity: The cross section of the 0.25 μm line and space pattern was observed with a scanning electron microscope.
It is indicated by the exposure amount (effective sensitivity) that becomes 1.

Resolution: The minimum line-and-space width at which the film was separated without reducing the film thickness at the effective exposure dose was measured with a scanning electron microscope.

[0051]

[Table 1]

As shown in Table 1, the use of a narrowly dispersible polymer according to the present invention significantly improves the resolution. Further, in the case of the example, the isolated pattern was formed in a significantly better shape than in the comparative example.

[0053]

According to the present invention, a resist composition containing a narrowly dispersible polymer obtained by a specific method according to the present invention can be used as a light source for deep ultraviolet (including excimer laser), electron beams, X-rays and radiation. In the exposure region of the energy radiation, excellent resolution is provided and an excellent isolated pattern is provided, so that a fine resist pattern with high precision can be formed.

Claims (7)

[Claims] (A) The following formula (I) (Wherein R represents alkyl having 1 to 12 carbons or alkanoyl having 1 to 12 carbons) in the presence of a free radical initiator and a stable free radical activator. After at least part of the group corresponding to -R of the narrow-dispersion polystyrene obtained by radical polymerization is eliminated, and the corresponding -OR part is converted to a hydroxyl group, an acid-labile group is obtained. A resin which is partially insoluble or hardly soluble in alkali by itself but becomes alkali-soluble by the action of an acid, (B) an acid generator, and (C) A chemically amplified positive resist composition comprising an organic solvent. 2. The composition according to claim 1, wherein the styrene derivative of the formula (I) is p-tert-butoxystyrene. 3. An acid-labile group which partially protects a hydroxyl group in the resin is selected from tert-butoxycarbonyl, tert-butoxycarbonylmethyl, 1-alkoxyalkyl and 2-residues of cyclic saturated ethers. The composition according to claim 1. 4. The resin has 0 to 30 mol% of a styrene unit having a group —OR at the p-position, and 10 to 50 mol% of a p-hydroxystyrene unit in which a hydroxyl group is protected by an acid-labile group. The composition according to any one of claims 1 to 3, wherein the composition comprises the remaining unprotected p-hydroxystyrene unit. 5. The composition according to claim 1, wherein said resin has a polydispersity of between 1.0 and 1.5. 6. A composition according to claim 5, wherein said resin has a weight average molecular weight of between 2,000 and 100,000. 7. The method according to claim 1, further comprising an organic base compound.
7. The composition according to any one of claims 6 to 6.