JP2002201232A - Polymer compound for photoresist and resin composition for photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polymer compound for photoresist which is excellent in dry etching resistance, adhesion to substrates, and alkali solubility and exhibits a high solubility in propylene glycol monomethyl ether acetate(PGMEA). SOLUTION: This polymer compound contains (A) 22-40 mol% monomer units represented by formula (I), (B) 20-38 mol% monomer units represented by formula (II), and (C) 22-58 mol% at least one kind of monomer units selected from monomer units represented by formulae (IIIa) and (IIIb). In those formulae, R is H or methyl; and R1, R2, and R3 are each independently a 1-3C alkyl.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer compound for a photoresist used for performing fine processing of a semiconductor and a resin composition for a photoresist containing the polymer compound.

[0002]

2. Description of the Related Art A photoresist resin used in a semiconductor manufacturing process has a portion exhibiting substrate adhesion and a portion which becomes soluble in an alkali developing solution by being desorbed by an acid generated from a photoacid generator upon exposure. As well as dry etching resistance.

[0003] Conventionally, an alicyclic hydrocarbon skeleton containing a lactone ring has been known as a structure that imparts substrate adhesion and has dry etching resistance. Further, an alicyclic hydrocarbon skeleton containing a tertiary carbon atom has been proposed as a structure that imparts acid elimination properties and has dry etching resistance. Therefore, by copolymerizing a monomer having these two skeletons, it is possible to obtain a polymer in which functions necessary for a photoresist resin are integrated. In particular, a resin in which all or most of the monomer units constituting the polymer have an alicyclic skeleton is preferable because of its high dry etching resistance.

On the other hand, propylene glycol monomethyl ether acetate (PGMEA) has come to be generally and standardly used as a resist solvent because of its low toxicity.

However, a resin in which all or most of the monomer units constituting the polymer have an alicyclic skeleton generally has low solubility in propylene glycol monomethyl ether acetate (PGMEA). There is a drawback that it is difficult to use. In addition, when a polymer containing a low molecular weight material such as a monomer or an oligomer is used as a photoresist resin,
In some cases, a fine pattern cannot be formed with high accuracy.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a photoresist for photoresist having high dry etching resistance, substrate adhesion and alkali solubility, and having high solubility in propylene glycol monomethyl ether acetate (PGMEA). An object of the present invention is to provide a polymer compound and a resin composition for a photoresist containing the polymer compound.

[0007] Another object of the present invention is to provide a polymer having a solubility in propylene glycol monomethyl ether acetate (PGMEA) even if all or most of the monomer units constituting the polymer have an alicyclic skeleton. An object of the present invention is to provide a high photoresist polymer compound and a photoresist resin composition containing the polymer compound.

It is still another object of the present invention to provide a polymer compound for a photoresist capable of forming a fine pattern with high accuracy, and a resin composition for a photoresist containing the polymer compound.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, a resin containing three types of monomer units having a specific structure having an alicyclic skeleton at a specific ratio has a high content. In addition to having dry etching resistance, substrate adhesion and alkali solubility, even though any of the monomer units contains an alicyclic skeleton,
The inventors have found that the compound has high solubility in propylene glycol monomethyl ether acetate (PGMEA), and completed the present invention.

That is, the present invention provides (A) a compound represented by the following formula (I):
22 to 40 mol% of a monomer unit represented by
(B) 20 units of the monomer unit represented by the following formula (II)
And (C) the following formulas (IIIa) and (IIIb):
At least one monomer unit selected from
Provided is a polymer compound for photoresist containing 2 to 58 mol%.

Embedded image (Wherein, R represents a hydrogen atom or a methyl group, and R ¹ , R ² ,
R ³ each independently represents an alkyl group having 1 to 3 carbon atoms.) In the formula (IIIa), R ¹ and R ² are preferably both methyl groups. R ³ in the formula (IIIb) is preferably a methyl group or an ethyl group. In a preferred embodiment of the polymer compound for a photoresist, the total content of the monomer units (A), (B) and (C) is 90 mol% or more of all monomer units constituting the polymer.

The present invention also provides (a) 22 to 40 mol% of a (meth) acrylic ester represented by the following formula (1), and (b) (meth) acrylic represented by the following formula (2). 20-38 mol% of an acid ester, and (c) the following formula (3a)
And a polymer compound for photoresist obtained by copolymerizing a monomer mixture containing 22 to 58 mol% of at least one (meth) acrylate selected from (3b).

Embedded image (Wherein, R represents a hydrogen atom or a methyl group, and R ¹ , R ² ,
R ³ each independently represents an alkyl group having 1 to 3 carbon atoms)

The polymer compound for a photoresist includes:
The monomer mixture containing the three (meth) acrylic esters of (a), (b) and (c) is copolymerized, and a solution containing the produced polymer is added to an organic solvent to cause precipitation or It includes a polymer compound for photoresist obtained by reprecipitation.

As the organic solvent used as the above-mentioned precipitation or reprecipitation solvent, for example, hydrocarbons, halogenated hydrocarbons, nitro compounds, nitriles, ethers, ketones, esters, carbonates, alcohols, carboxylic acids or a mixture containing these solvents Solvents and the like can be used. The organic solvent used as the above-mentioned precipitation or reprecipitation solvent preferably contains at least a hydrocarbon. The solubility parameter of the organic solvent used as the above-mentioned precipitation or reprecipitation solvent according to the Fedors method is, for example, 7.0.
(Cal / cm ³ ) ^1/2 -14.0 (cal / cm ³ ) ^1/2
It is preferably in the range of ^{[14.3MPa 1/2 ~28.6MPa 1/2]} .

The present invention also provides a photoresist resin composition comprising at least the above-mentioned polymer compound for photoresist and a photoacid generator. The photoresist resin composition may contain propylene glycol monomethyl ether acetate as a solvent.

In this specification, "acryl" and "methacryl" may be collectively referred to as "(meth) acryl", and "acryloyl" and "methacryloyl" may be collectively referred to as "(meth) acryloyl".

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer compound for a photoresist according to the present invention contains 22 to 40 mol% of a monomer unit (A) represented by the above formula (I) in a polymer molecule. The monomer unit (B) represented by 20 to 38
Mol%, and at least one monomer unit (C) selected from the formulas (IIIa) and (IIIb),
Contains 8 mol%.

Since the monomer unit (A) has a lactone ring and the monomer unit (B) has a hydroxyl group in the ring, both units function as an adhesion-imparting unit for increasing the adhesion to the substrate. On the other hand, in the monomer unit (C), the oxygen atom constituting the ester bond is
Since the site containing the adamantane skeleton is released from the carboxylic acid portion bonded to the main chain by an acid to generate a free carboxyl group because it is bonded to a secondary carbon atom, as an alkali-soluble unit that is solubilized during alkali development Function. Further, since each of the monomer units (A), (B) and (C) has an alicyclic skeleton, the polymer composed of these monomer units has extremely high dry etching resistance.

And monomer units (A) and (B)
And a polymer compound containing (C) in the above range, although propylene glycol monomethyl ether generally used as a solvent for a resist, despite that each of the monomer units has an alicyclic skeleton. It has a very advantageous feature of high solubility in acetate. Therefore, it can be suitably used as a photoresist resin. When the proportion of each monomer unit is out of the above range, the solubility of the polymer in propylene glycol monomethyl ether acetate is greatly reduced.

The preferable ratio of each monomer unit to all monomer units constituting the polymer is 25 to 35 mol% for the monomer unit (A), 25 to 35 mol% for the monomer unit (B), and C) is about 30 to 50 mol%.

In the above formulas (IIIa) and (IIIb), R ¹ ,
Examples of the alkyl group having 1 to ³ carbon atoms for R ² and R ³ include:
Examples include a methyl group, an ethyl group, a propyl group, and an isopropyl group. R ¹ and R ² are particularly preferably a methyl group, and R ³ is particularly preferably a methyl group or an ethyl group.

The polymer compound for a photoresist of the present invention comprises the monomer units (A), (B) and (C)
And may include other monomer units. In a preferred embodiment of the present invention, the total content of the monomer units (A), (B) and (C) is at least 90 mol%, more preferably at least 95 mol%, particularly preferably at least 9 mol% of all monomer units constituting the polymer.
8 mol% or more (for example, 100 mol%). Further, in another preferred embodiment of the present invention, not only the adamantane skeleton and norbornene skeleton but also a monomer unit having an alicyclic skeleton is included in 90 mol% or more of all monomer units. The polymer compounds of these preferred embodiments are particularly excellent in dry etching resistance.

In the present invention, the weight average molecular weight (Mw) of the polymer compound is, for example, about 1,000 to 500,000, preferably about 3,000 to 50,000, and more preferably about 5,000 to 20,000. Yes, the molecular weight distribution (M
w / Mn) is, for example, about 1.5 to 3.5. Here, Mn indicates a number average molecular weight (in terms of polystyrene).

Formulas (I), (II), (IIIa) and (III)
Each monomer unit represented by b) can be formed by subjecting the corresponding (meth) acrylic acid ester to polymerization as a comonomer. That is, the polymer compound for photoresist of the present invention comprises (a) 22 to 40 mol% of the (meth) acrylate represented by the formula (1), and (b) represented by the formula (2). 20-38 mol% of (meth) acrylic acid ester, and (c) the formula (3a)
And (3b) can be obtained by copolymerizing a monomer mixture containing 22 to 58 mol% of at least one (meth) acrylic acid ester selected from (3b).

The compound represented by the formula (1) includes 5-acryloyloxy-2,6-norbornanecarboractone (= 4-acryloyloxy-6-oxatricyclo [3.2.1.1 ^3,8 ] Nonan-7-one), 5-methacryloyloxy-2,6-norbornanecarboractone (= 4-methacryloyloxy-6-oxatricyclo [3.2.1.1 ^3,8 ] nonan-7-one) Is included. These monomers can be used alone or in combination of two kinds.

The compound represented by the formula (2) includes 1-acryloyloxy-3-hydroxyadamantane and 1-methacryloyloxy-3-hydroxyadamantane. These monomers can be used alone or in combination of two kinds.

A typical compound represented by the formula (3a) is, for example, 1- (2-acryloyloxy-2-propyl) adamantane [= 1- (1-acryloyloxy-1-methylethyl) adamantane] , 1- (2-methallyloyloxy-2-propyl) adamantane [= 1-
(1-methacryloyloxy-1-methylethyl) adamantane], 1- (1-acryloyloxy-1-methylpropyl) adamantane, 1- (1-methacryloyloxy-1-methylpropyl) adamantane, 1- (1
-Acryloyloxy-1-ethylpropyl) adamantane, 1- (1-methacryloyloxy-1-ethylpropyl) adamantane, 1- (1-acryloyloxy-1-methylbutyl) adamantane, 1- (1-methacryloyloxy-1-) Methyl butyl) adamantane and the like. These monomers can be used alone or in combination of two or more.

The compounds represented by the formula (3b) include 2-acryloyloxy-2-methyladamantane, 2-methacryloyloxy-2-methyladamantane, 2-acryloyloxy-2-ethyladamantane, 2-ethyl-
2-methacryloyloxyadamantane is included. These monomers can be used alone or in combination of two or more.

The polymerization can be carried out by a conventional method used for producing an acrylic polymer, such as solution polymerization or melt polymerization. Known solvents can be used as the polymerization solvent, for example, ethers (chain ethers such as diethyl ether, cyclic ethers such as tetrahydrofuran, dioxane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, etc.), ketones (Acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), amide (N, N-dimethylacetamide, N, N-dimethylformamide, etc.), sulfoxide (dimethylsulfoxide, etc.), alcohol (methanol, ethanol, propanol, etc.), hydrocarbon (benzene, etc.) , Aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, alicyclic hydrocarbons such as cyclohexane, etc.), and mixed solvents thereof. Further, a known polymerization initiator can be used as the polymerization initiator. The polymerization temperature is, for example, 3
It can be appropriately selected within a range of about 0 to 150 ° C.

The polymer compound for a photoresist of the present invention is preferably obtained by copolymerizing a monomer mixture containing the above three types of (meth) acrylates (a), (b) and (c), A polymer compound for photoresist obtained by adding a solution containing the produced polymer (for example, a solution of the polymerization solvent) to an organic solvent to precipitate or reprecipitate the solution. In such a photoresist polymer compound, a low molecular weight substance such as a monomer or an oligomer is dissolved in an organic solvent and easily removed during the precipitation and / or reprecipitation operation. In this case, a fine pattern can be accurately formed.
When water is used as a solvent for precipitation or reprecipitation during the precipitation or reprecipitation operation, the low-molecular-weight substance cannot be sufficiently removed because it is difficult to dissolve in water. for that reason,
When the obtained polymer compound is used as a photoresist resin, a fine pattern may not be formed with high accuracy.

Examples of the organic solvent used as the above-mentioned precipitation or reprecipitation solvent include hydrocarbons (pentane, hexane,
Aliphatic hydrocarbons such as heptane and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene),
Halogenated hydrocarbons (halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene), nitro compounds (nitromethane, nitroethane, etc.), nitriles (acetonitrile, Benzonitrile, etc.), ethers (chain ethers such as diethyl ether, diisopropyl ether, dimethoxyethane; cyclic ethers such as tetrahydrofuran, dioxane), ketones (acetone, methyl ethyl ketone, diisobutyl ketone, etc.), esters (ethyl acetate, butyl acetate, etc.) ,
Examples thereof include carbonates (dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), alcohols (methanol, ethanol, propanol, isopropyl alcohol, butanol, etc.), carboxylic acids (acetic acid, etc.), and mixed solvents containing these solvents.

Among them, as the organic solvent used as the precipitation or reprecipitation solvent, a solvent containing at least a hydrocarbon (particularly, an aliphatic hydrocarbon such as hexane) is preferable. In such a solvent containing at least hydrocarbon, the ratio of hydrocarbon (for example, aliphatic hydrocarbon such as hexane) to another solvent is, for example, the former / the latter (volume ratio; 25 ° C.)
= 10/90 to 99/1, preferably the former / latter (volume ratio; 25 ° C) = 30/70 to 98/2, more preferably the former / latter (volume ratio; 25 ° C) = 50/50 to 97 /.
It is about 3.

The solubility parameter (hereinafter sometimes simply referred to as “SP value”) of the organic solvent used as the precipitation or reprecipitation solvent according to the Fedors method is as follows:
7.0 (cal / cm ³ ) ^{1/2 to} 14.0 (cal / cm ³ )
³ ) ^1/2 [14.3 MPa ^{1/2 to} 28.6 MPa ^1/2 ] is preferable. When such an organic solvent is used as a precipitation or reprecipitation solvent, a polymer compound having a composition distribution particularly suitable as a photoresist resin can be obtained.

The SP value of the organic solvent is described, for example, in "Polymer Handbook", 4th edition, VI
It can be determined by the method described on pages I-675 to VII-711. Further, as the SP value of the organic solvent, Table 1 (page VII-683) and Tables 7 to 8 (pages VII-688 to VII-711) of the document are used.
Can be adopted. When the organic solvent is a mixed solvent of a plurality of solvents, the SP value can be determined by a known method. For example, the SP value of the mixed solvent can be determined as the sum of the products of the SP value of each solvent and the volume fraction, assuming that additivity is satisfied.

The SP value of the organic solvent is more preferably from 7.0 (cal / cm ³ ) ^{1/2 to} 9.0 (cal / c).
m ³ ) ^1/2 [14.3 MPa ^{1/2 to} 18.4 MPa ^1/2 ],
And 12.0 (cal / cm ³ ) ^{1/2 to} 14.0 (cal
^{/ Cm 3) 1/2 [24.5MPa 1} /2 ~28.6MP
a ^1/2 ], particularly preferably 7.5 (cal
/ Cm ³ ) ^{1/2 to} 8.5 (cal / cm ³ ) ^1/2 [15.3
MPa ^1/2 ~17.4MPa ^1/2], and 13.0 (ca
1 / cm ³ ) ^1/2 -14.0 (cal / cm ³ ) ^1/2 [2
6.6 MPa ^{1/2 to} 28.6 MPa ^1/2 ].

The photoresist resin composition of the present invention comprises:
It contains at least the polymer compound for photoresist of the present invention and a photoacid generator.

Examples of the photoacid generator include commonly used or known compounds that efficiently generate an acid upon exposure, such as diazonium salts, iodonium salts (eg, diphenyliodohexafluorophosphate), and sulfonium salts (eg, triphenylsulfonium). Hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium methanesulfonate, etc.), sulfonic acid ester [for example, 1-phenyl-1- (4-methylphenyl) sulfonyloxy-1
-Benzoylmethane, 1,2,3-trisulfonyloxymethylbenzene, 1,3-dinitro-2- (4-phenylsulfonyloxymethyl) benzene, 1-phenyl-1- (4-methylphenylsulfonyloxymethyl)
-1-hydroxy-1-benzoylmethane, etc.], oxathiazole derivatives, s-triazine derivatives, disulfone derivatives (eg, diphenyldisulfone), imide compounds, oxime sulfonates, diazonaphthoquinone, benzoin tosylate, and the like. These photoacid generators can be used alone or in combination of two or more.

The amount of the photoacid generator used can be appropriately selected according to the strength of the acid generated by light irradiation, the ratio of each monomer unit in the polymer compound, and the like. For example, based on 100 parts by weight of the polymer compound 0.1 to 30 parts by weight, preferably 1 to 25 parts by weight, more preferably about 2 to 20 parts by weight.

The resin composition for a photoresist includes an alkali-soluble component such as an alkali-soluble resin (eg, a novolak resin, a phenol resin, an imide resin, and a carboxyl group-containing resin), a coloring agent (eg, a dye), and an organic solvent. (Eg, hydrocarbons, halogenated hydrocarbons, alcohols, esters, amides, ketones, ethers, cellosolves, carbitols, glycol ether esters, mixed solvents thereof, and the like). May be.

After coating the photoresist resin composition on a substrate or substrate and drying, the coating film (resist film) is exposed to a light beam through a predetermined mask (or further baked after exposure). The fine pattern can be formed with high precision by forming a latent image pattern and then developing.

As the substrate or substrate, a silicon wafer,
Examples include metal, plastic, glass, and ceramic. The application of the resin composition for a photoresist can be performed using a conventional application means such as a spin coater, a dip coater, and a roller coater. The thickness of the coating film is, for example, about 0.1 to 20 μm, and preferably about 0.3 to 2 μm.

Light of various wavelengths, such as ultraviolet rays and X-rays, can be used for exposure. For semiconductor resists, g-rays, i-rays, excimer lasers (eg, XeC
1, KrF, KrCl, ArF, ArCl, etc.) are used. Exposure energy is, for example, 1 to 1000 m
J / cm ² , preferably about 10 to 500 mJ / cm ² .

An acid is generated from the photoacid generator by light irradiation,
By this acid, for example, a protective group (leaving group) such as a carboxyl group of the alkali-soluble unit of the polymer compound is rapidly eliminated, and a carboxyl group or the like contributing to solubilization is generated. Therefore, a predetermined pattern can be accurately formed by development with water or an alkali developing solution.

[0043]

According to the present invention, since three types of monomer units having a specific structure having an alicyclic skeleton are contained in a specific ratio, only high dry etching resistance, substrate adhesion and alkali solubility can be obtained. And high solubility in propylene glycol monomethyl ether acetate (PGMEA), which is suitable as a resist solvent. Therefore, it is suitable as a photoresist resin. Also,
A fine pattern can be formed with high accuracy.

The polymer compound for a photoresist of the present invention can be used in propylene glycol monomethyl ether acetate (PGMEA) even if all or most of the monomer units constituting the polymer are monomer units having an alicyclic skeleton. On the other hand, it shows high solubility.

[0045]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. The number at the lower right of the parenthesis in the structural formula indicates the mol% of the monomer unit.

Example 1 Synthesis of a resin having the following structure

Embedded image 1.38 g (6.22 mmol) of 5-methacryloyloxy-2,6-norbornanecarboractone and 1- (2-methacryloyloxy-2-) were placed in a 100 ml round bottom flask equipped with a reflux tube, a stirrer, and a three-way cock. Propyl) adamantane 2.16 g (8.24 mmol), 1
1.46 g (6.19 mmol) of methacryloyloxy-3-hydroxyadamantane and 0.50 g of an initiator (V-65 manufactured by Wako Pure Chemical Industries) were added, and dissolved in 16.00 g of THF (tetrahydrofuran). Subsequently, after the inside of the flask was replaced with dry nitrogen, the temperature of the reaction system was raised to 60 ° C.
And stirred for 6 hours under a nitrogen atmosphere. The reaction solution was a 9: 1 (volume ratio; 25 ° C.) mixture of hexane and ethyl acetate [SP value: 7.65 (cal / cm ³ ) ^1/2 (= 15.6).
4 MPa ^1/2 )] and purified by filtering off the resulting precipitate. The collected precipitate was dried under reduced pressure, dissolved again in 16.00 g of THF, and the above-mentioned precipitation purification operation was repeated to obtain 3.55 g of a desired resin. GPC analysis of the recovered polymer revealed a Mw
(Weight average molecular weight) is 7800, molecular weight distribution (Mw / M
n) was 2.15. ¹ H-NMR (DMSO-d ₆
In the (middle) analysis, in addition to 1.5-2.5 ppm (broad), strong signals were observed at 3.1 ppm, 4.6 ppm, and 4.7 ppm.

Comparative Example 1 Synthesis of resin having the following structure

Embedded image 2.06 g (9.28 mmol) of 5-methacryloyloxy-2,6-norbornanecarboractone and 1- (2-methacryloyloxy-2-) were placed in a 100 ml round bottom flask equipped with a reflux tube, a stirrer, and a three-way cock. Propyl) adamantane 1.54 g (5.88 mmol), 1
-0.40 g (1.69 mmol) of methacryloyloxy-3-hydroxyadamantane and 0.40 g of an initiator (V-65 manufactured by Wako Pure Chemical Industries) were added, and dissolved in 16.00 g of THF (tetrahydrofuran). Subsequently, after the inside of the flask was replaced with dry nitrogen, the temperature of the reaction system was raised to 60 ° C.
And stirred for 6 hours under a nitrogen atmosphere. A 9: 1 (volume ratio; 25 ° C.) mixed solution of hexane and ethyl acetate 5
The solution was dropped to 00 ml and the resulting precipitate was separated by filtration for purification. After drying the collected precipitate under reduced pressure, the THF1
The resin was dissolved in 6.00 g, and 3.22 g of a desired resin was obtained by repeating the above-mentioned precipitation purification operation. GPC analysis of the recovered polymer showed a Mw (weight average molecular weight) of 7,600 and a molecular weight distribution (Mw / Mn) of 2.00.
Met. ^{In 1} H-NMR (in DMSO-d ₆ ) analysis,
In addition to 1.5-2.5 ppm (broad), 3.1 pp
m, 4.6 ppm, and a strong signal were observed at 4.7 ppm.

Comparative Example 2 Synthesis of resin having the following structure

Embedded image 0.91 g (4.10 mmol) of 5-methacryloyloxy-2,6-norbornanecarboractone and 1- (2-methacryloyloxy-2-) were placed in a 100 ml round bottom flask equipped with a reflux tube, a stirrer, and a three-way cock. Propyl) adamantane 2.15 g (8.21 mmol), 1
1.94 g (8.22 mmol) of methacryloyloxy-3-hydroxyadamantane and 0.50 g of an initiator (V-65 manufactured by Wako Pure Chemical Industries) were added, and dissolved in 16.00 g of THF (tetrahydrofuran). Subsequently, after the inside of the flask was replaced with dry nitrogen, the temperature of the reaction system was raised to 60 ° C.
And stirred for 6 hours under a nitrogen atmosphere. A 9: 1 (volume ratio; 25 ° C.) mixed solution of hexane and ethyl acetate 5
The solution was dropped to 00 ml, and the resulting precipitate was separated by filtration for purification. After drying the collected precipitate under reduced pressure, the THF1
The resultant was dissolved in 6.00 g, and 3.41 g of a desired resin was obtained by repeating the above-mentioned precipitation purification operation. GPC analysis of the recovered polymer showed a Mw (weight average molecular weight) of 8000 and a molecular weight distribution (Mw / Mn) of 2.08.
Met. ^{In 1} H-NMR (in DMSO-d ₆ ) analysis,
In addition to 1.5-2.5 ppm (broad), 3.1 pp
m, 4.6 ppm, and a strong signal were observed at 4.7 ppm.

Evaluation Test For each of the polymers obtained in the above Examples and Comparative Examples, 100 parts by weight of the polymer and 10 parts by weight of triphenylsulfonium hexafluoroantimonate were mixed with propylene glycol monomethyl ether acetate (PG
MEA) to prepare a photoresist resin composition having a polymer concentration of 17% by weight. However, the polymer obtained in Comparative Example did not dissolve in PGMEA and could not be subjected to exposure evaluation. The photoresist resin composition prepared using the polymer obtained in the example was applied to a silicon wafer by a spin coating method to form a photosensitive layer having a thickness of 1.0 μm. After prebaking on a hot plate at a temperature of 100 ° C. for 150 seconds, a wavelength of 247
After exposing at a dose of 30 mJ / cm ² through a mask using a KrF excimer laser of 10 nm, the substrate was post-baked at a temperature of 100 ° C. for 60 seconds. Next, 6 M with an aqueous solution of 0.3 M tetramethylammonium hydroxide.
After developing for 0 seconds and rinsing with pure water, 0.20 μm
The line and space pattern was obtained.

Claims (11)

[Claims] (A) 22 to 40 mol% of a monomer unit represented by the following formula (I), (B) 20 to 38 mol% of a monomer unit represented by the following formula (II), and (C) A) a polymer compound for a photoresist containing 22 to 58 mol% of at least one monomer unit selected from the following formulas (IIIa) and (IIIb): Embedded image (Wherein, R represents a hydrogen atom or a methyl group, and R ¹ , R ² ,
R ³ each independently represents an alkyl group having 1 to 3 carbon atoms) 2. The polymer compound for a photoresist according to claim 1, wherein both R ¹ and R ² in the formula (IIIa) are methyl groups. 3. The polymer compound according to claim 1, wherein R ³ in the formula (IIIb) is a methyl group or an ethyl group. 4. The photoresist composition according to claim 1, wherein the total content of the monomer units (A), (B) and (C) is at least 90 mol% of all the monomer units constituting the polymer. Molecular compound. 5. (a) (meth) represented by the following formula (1)
22 to 40 mol% of acrylic acid ester, and (b) 20 to 40% of (meth) acrylic acid ester represented by the following formula (2)
(C) a photo-polymer obtained by copolymerizing a monomer mixture containing 22 to 58 mol% of at least one (meth) acrylate selected from the following formulas (3a) and (3b): High molecular compound for resist. Embedded image (Wherein, R represents a hydrogen atom or a methyl group, and R ¹ , R ² ,
R ³ each independently represents an alkyl group having 1 to 3 carbon atoms) 6. A monomer mixture containing three types of (meth) acrylates (a), (b) and (c) is copolymerized, and a solution containing the resulting polymer is added to an organic solvent. The polymer compound for a photoresist according to claim 5, which is obtained by precipitation or reprecipitation. 7. The organic solvent used as a precipitation or reprecipitation solvent is a hydrocarbon, a halogenated hydrocarbon, a nitro compound,
The photoresist polymer compound according to claim 6, wherein the polymer compound is a nitrile, an ether, a ketone, an ester, a carbonate, an alcohol, a carboxylic acid, or a mixed solvent containing these solvents. 8. The photoresist polymer compound according to claim 6, wherein the organic solvent used as the precipitation or reprecipitation solvent contains at least a hydrocarbon. 9. An organic solvent used as a precipitation or reprecipitation solvent having a solubility parameter value of 7.0 (cal / cm ³ ) ^{1/2 to} 14.0 (cal / c) according to the Fedors method.
The polymer compound for a photoresist according to claim 6, wherein m ³ ) ^1/2 [14.3 MPa ^{1/2 to} 28.6 MPa ^1/2 ]. 10. A photoresist resin composition comprising at least the photoresist polymer compound according to claim 1 and a photoacid generator. 11. The photoresist resin composition according to claim 10, which comprises propylene glycol monomethyl ether acetate as a solvent.