KR20040016161A - Process for preparing polymer compound for resist - Google Patents

Abstract

PURPOSE: A method for preparing a polymer compound for resist is provided, to improve heat resistance, sensitivity and resolution without the shrinkage of a resist layer, the decrease of a resist line width and the deterioration of dry etching resistance of a polymer. CONSTITUTION: The method comprises the steps of dissolving a styrene-based monomer containing at least 4-acetoxystyrene monomer and a dimethyl-2,2-azobiscarboxylic acid ester in a solvent to obtain a polymer solution; hydrolyzing the polymer with an alkali catalyst; and washing the obtained product with water. Preferably the dimethyl-2,2-azobiscarboxylic acid ester is dimethyl-2,2-azobis(2-methylpropionate); and the styrene-based monomer is represented by the formula 1, wherein R1 is H, OH, an alkyl or alkoxy group of C1-C6 or an acyloxy group of C2-C7; and R2 is H or CH3. Preferably the solvent does not contain methanol; and the alkali catalyst is a quaternary amine hydroxide.

Description

Manufacturing method of polymer compound for resists {PROCESS FOR PREPARING POLYMER COMPOUND FOR RESIST}

The present invention relates to a method for producing a polymer compound for resist, and more particularly, to a method for producing a polymer compound for resist useful as a precursor for obtaining a photosensitive resin such as a resist or a photosensitive resin.

Homopolymers, copolymers and the like of 4-hydroxystyrene are known as photosensitive resins such as resists or precursors for obtaining such photosensitive resins.

As a method for producing such a polymer, for example, "4-acetoxystyrene polymer dissolved in methanol is quaternary ammonium for a time sufficient to produce a phenol group by hydrolyzing the acetoxy group at a temperature of about 40 to 80 ℃. React with base; Subsequently, the method for producing a vinyl phenol polymer, wherein the decomposition product of methyl acetate and quaternary ammonium hydroxide produced during the reaction is removed by heating from about 50 ° C to 150 ° C '' (Japanese Patent Application Laid-Open No. 7-96569) This is known.

However, in order to improve resist performance, such as heat resistance, sensitivity, and resolution, conventionally, the composition ratio of the polymer or the molecular weight of the polymer is adjusted, or the residues dissolved in the alkaline solution are reduced, or in particular, the resolution of the polymer by a specific compound is used to improve the resolution. It has been modified.

However, when the polymer composition ratio is adjusted or the polymer is made hydrophilic by deformation, there is a problem that the film of the resist is reduced or the resist line width is reduced. In addition, when the molecular weight of the polymer is reduced, the solubility in the alkali solution is improved, but there is a problem that the dry etching resistance of the polymer is lowered.

In addition, in the technique disclosed in Japanese Unexamined Patent Publication No. 7-96569, it is possible to remove the remaining alkali metal, which is a problem in the use or use of the 4-hydroxy styrene polymer, but the film of the resist is reduced, It was difficult to improve resist performances such as heat resistance, sensitivity, resolution, and the like without reducing the line width and reducing the dry etching resistance of the polymer.

Accordingly, the present invention provides a preparation of a polymer compound for resists that makes it possible to improve resist performance such as heat resistance, sensitivity and resolution without reducing the resist film, decreasing the resist line width, or lowering the dry etching resistance of the polymer. It is an object to provide a method.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, in the polymer solution which makes at least 4-acetoxy styrene-type monomer obtained by using dimethyl-2, 2- azobiscarboxylic acid ester as a polymerization initiator as one of a constituent monomer, After adding an alkali catalyst to hydrolyze and washing with water, the above-mentioned problem was solved, and the present invention was completed.

That is, in the present invention, an alkali catalyst is added to a polymer solution obtained by dissolving a styrene-based monomer containing at least 4-acetoxy styrene monomer and dimethyl-2,2-azobiscarboxylic acid ester in a solvent to polymerize a styrene-based monomer. After decomposing, the present invention provides a method for producing a polymer compound for resist, which is washed with water.

By applying such a structure, a high-molecular compound for resist that can improve resist performance such as heat resistance, sensitivity, resolution, and the like without reducing the resist film, decreasing the resist line width, or lowering the dry etching resistance of the polymer can be obtained. .

The styrene-based monomer used in the present invention contains at least 4-acetoxy styrene monomer. As a styrene-type monomer, the compound represented by following formula (1) is preferable.

(In formula, R <^1> represents a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, or a C2-C7 acyloxy group, and R <^2> represents a hydrogen atom or a methyl group. Is displayed.)

The alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the acyloxy group having 2 to 7 carbon atoms may be linear or branched. As R <^1> , a hydroxyl group, a C3-C5 alkoxy group, and a C2-C4 acyloxy group are more preferable, and a hydroxyl group, t-butoxy group, and an acetoxy group are especially suitable.

In this invention, one or more types of 4-acetoxy styrene monomer and the said styrene-type monomer can also be used as needed.

Dimethyl-2,2 azobiscarboxylic acid ester is used as a polymerization initiator for polymerizing the styrene monomer. As the carboxylic acid residue constituting such dimethyl-2,2 azobiscarboxylic acid ester, any linear or branched chain may be used, but one having 2 to 8 carbon atoms is preferable, and one having 2 to 5 carbon atoms is more suitable. Methyl propoxy group is particularly preferred. By using dimethyl-2,2-azobiscarboxylic acid ester as a polymerization initiator, resist performance such as heat resistance, sensitivity, resolution, etc. can be improved without reducing the resist film, reducing the resist line width, or reducing the dry etching resistance of the polymer. A polymer compound for resists can be obtained. In the case of using, for example, 2,2-azobisisobutyronitrile as the polymerization initiator, the above excellent effects cannot be sufficiently obtained.

In the production method of the present invention, first, a styrene-based monomer containing at least 4-acetoxy styrene monomer and dimethyl-2,2-azobiscarboxylic acid ester are dissolved in a solvent to polymerize a styrene-based monomer to form a styrene-based monomer. A polymer is prepared.

The solvent for polymerizing the styrene monomer by dissolving the styrene monomer and the dimethyl-2,2-azobiscarboxylic acid ester is not particularly limited as long as it dissolves them. A general solvent may be used but it does not contain methanol. Do. Specifically, ethylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, etc. are mentioned, for example.

The polymerization can be carried out by a method such as solution polymerization, suspension polymerization, emulsion polymerization or bulk polymerization using a known free radical catalyst such as a peroxide (peroxide) or an azo compound.

As for the compounding ratio (molar ratio) of a styrene-type monomer and a dimethyl-2, 2- azobis carboxylic acid ester, 100: 1-100: 30 are suitable, and 100: 2-100: 20 are especially preferable. 1-150 degreeC is suitable for reaction conditions, Especially room temperature (25 degreeC)-100 degreeC is preferable, A suitable time is 1 to 48 hours, and 3 to 24 hours are the most preferable. It is preferable to carry out nitrogen substitution in the reaction vessel so as not to lose the activity of radicals.

By selecting these reaction conditions suitably, the polymer of the suitable molecular weight suitable for a use can be manufactured.

Next, an alkali catalyst is added to the obtained polymer solution and hydrolyzed to prepare a hydroxy styrene polymer. As an alkali catalyst, quaternary amine hydroxide is suitable. The quaternary amine hydroxide is represented by the following formula.

Herein, each R is an organic group having 1 to 9 carbon atoms. R may be aliphatic or aromatic and may be the same or different. Organic groups may also include hydroxy ethyl. Examples of organic groups are methyl, ethyl, isopropyl, butyl, benzyl, methyl benzyl, dimethyl benzyl. Examples of useful quaternary ammonium hydroxides are tetramethyl ammonium hydroxide, ethyl trimethyl ammonium hydroxide, diethyl dimethyl ammonium hydroxide, triethyl methyl ammonium hydroxide, tetraethyl ammonium hydroxide, benzyl trimethyl ammonium hydroxide and choline. Particularly preferred quaternary ammonium hydroxides are tetramethyl ammonium hydroxides.

The addition amount of an alkali catalyst is 1-20 weight% with respect to the styrene-type monomer compounding quantity.

Is suitable, with 1 to 5% by weight being particularly preferred. As for the conditions of hydrolysis, 20-100 degreeC is suitable, 20-80 degreeC is especially preferable, 1-10 hours suitably, 3-8 hours are the most suitable suitably.

Next, the obtained hydroxystyrene polymer containing liquid is wash | cleaned with water. By washing with water, a polymer compound for resist can be produced that can improve resist performance such as heat resistance, sensitivity, resolution, and the like without reducing the resist film, decreasing the resist line width, or decreasing the dry etching resistance of the polymer. Can be. Since the quaternary ammonium hydroxide is unstable in heating, since it is decomposed after the hydrolysis reaction to become a low boiling point decomposition product, there is an advantage that the quaternary ammonium hydroxide is easily removed from the reaction solution. However, it is difficult to completely remove the quaternary ammonium hydroxide only by decomposition and removal by heating. Therefore, when using the decomposition removal by heating instead of the method of washing with water, the said excellent effect cannot fully be acquired. Water can be added and washed in any amount and at any number of times. There is no particular limitation on the temperature at the time of addition. You may mix | blend methanol with water at a suitable ratio.

After washing with water, the polymer compound for resist can be obtained by performing purification, drying, etc. according to a conventional method.

4-acetoxy styrene can be homopolymerized easily like homopolymerization of styrene, or can be copolymerized with styrene and another monomer copolymerizable with styrene.

In the present invention, compounds other than the styrene monomer can be copolymerized with the styrene monomer. Examples of such compounds include diene monomers such as vinyl toluene, α-methyl styrene, butadiene, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate and 2-ethyl hexyl acrylate. And polymerizable acids such as acrylate and methacrylate monomers, acrylic acid, methacrylic acid, maleic anhydride, maleic acid, and fumaric acid.

(In formula, R <^3> represents a hydrogen atom or a methyl group, R <^4> is a C1-C6 alkyl group or any of following formula (3)-(7).

Is represented). By polymerizing the compound represented by Formula (2) as a monomer, the effect of a resolution improvement is produced. There is no restriction | limiting in particular in the compounding ratio of a styrene-type monomer and the compound represented by Formula (2).

The high molecular compound for resist manufactured by the method of this invention is useful as resin for resist used for resist pattern formation. The resist pattern is formed by, for example, preparing a resist liquid containing a high molecular compound for photoresist, a photoacid generator and a solvent (for example, ethyl lactate), applying the resist liquid on a substrate to form a resist film, and exposing the resist film. It can form by developing.

Next, the present invention will be described in more detail by showing examples, but the present invention is not limited to the following examples.

(Example 1)

(Preparation of 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer using dimethyl-2,2-azobis (2-methylpropionate) as polymerization initiator)

In a separate flask, 100 g of ethylene glycol monoethyl ether, 78.6 g of 4-acetoxy styrene, 21.4 g of 4-tert-butoxy styrene, and 3.7 g of dimethyl-2,2 azobis (2-methylpropionate) as a polymerization initiator were added. After nitrogen replacement, the mixture was reacted at 80 ° C. for 16 hours. 5g of 25% tetramethylammonium hydroxide is added to this reaction liquid, and it heats at 70 degreeC for 5 hours. To remove the low molecular weight oligomer and residual monomer, the solution was washed several times by adding methanol / pure water at an arbitrary ratio. After washing, solvent substitution was carried out in propylene glycol monomethyl ether acetate to obtain 400 g of a propylene glycol monomethyl ether acetate solution of 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer having a solid content of 20%. The molecular weight of the obtained polymer was 30000.

(Example 2)

(Preparation of Substituted 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer using dimethyl-2,2-azobis (2-methylpropionate) as polymerization initiator)

To 100 g of propylene glycol monomethyl ether acetate solution of 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer obtained in Example 1, 1.1 g of ethyl vinyl ether and 0.17 g of trifluoroacetic acid were added after nitrogen substitution, and room temperature Reaction was carried out for 5 hours. 0.3 g of triethylamine was added to the obtained reaction solution and neutralized. After neutralization, pure water was added to the reaction solution and washed. This washing was repeated several times. After washing, dehydration was carried out in vacuo, solvent substitution was performed with ethyl lactate, and 100 g of an ethyl lactate solution of the substituted 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer was obtained.

(Comparative Examples 1 and 2)

Comparative Example 1 was similar to Example 1 in Example 1 except that 2,2-azobisisobutyronitrile was used instead of dimethyl-2,2-azobis (2-methylpropionate). 400 g of a propylene glycol monomethyl ether acetate solution of hydroxystyrene / 4-tertiarybutoxystyrene polymer was obtained. The molecular weight of the obtained polymer is 30000.

Comparative Example 2 was similar to Example 2 in Example 2, except that 2,2-azobisisobutyronitrile was used instead of dimethyl-2,2-azobis (2-methylpropionate). 100 g of ethyl lactate solution of the substituted 4-hydroxystyrene / 4-tert-butoxy styrene polymer was obtained.

Experimental Example 1

(Formation of resist pattern)

5 g of a photoacid generator bis (cyclohexylsulfonyl) diazomethane was dissolved in 100 g of an ethyl lactate solution of the substituted 4-hydroxystyrene / 4-tertiarybutoxystyrene polymer obtained in Example 2 and Comparative Example 2, and a resist solution. Were combined. This resist liquid was filtered using a 0.1 micrometer membrane filter to obtain a resist liquid. This resist liquid was applied onto a silicon substrate using a spinner, and dried at 90 ° C. for 90 seconds on a hot plate to prepare a resist film having a thickness of 0.5 μm. After exposing this film | membrane using a reduced-projection exposure apparatus, it heated at 110 degreeC and 90 second, and then developed in 2.38% aqueous tetramethyl ammonium hydroxide solution for 30 second, and rinsed with pure water.

In the post-development resist pattern, pattern shape, resolution, sensitivity, dissolved residue and heat resistance were evaluated by the following method. The results are shown in Table 1.

(Pattern shape)

After leaving the silicon substrate with a resist pattern after development for 30 seconds in a clean oven set at various temperatures, the shape of the resist pattern was observed with a scanning electron microscope.

(resolution)

When the exposure amount which resolves the line-and-space of 0.25 micrometer 1: 1 to the optimal exposure, the minimum line width of the separated line-and-space was made into the resolution of the evaluation resist.

(Sensitivity)

The exposure amount which resolves the line-and-space of 0.25 micrometer 1: 1 to the optimal exposure amount was shown.

(Melting residue)

SEM (scanning electron microscope) photograph was used to determine the presence or absence.

(Heat resistance)

When the resist pattern was heated, it was shown at the temperature at which the resist pattern caused thermal deformation.

TABLE 1

In Table 1, it became clear that the use of the resist polymer compound prepared according to the method of the present invention can improve resist performance such as heat resistance, sensitivity, and resolution.

By using the production method of the present invention, a high-molecular compound for resist that can enhance resist performance such as heat resistance, sensitivity, resolution, and the like without reducing the resist film, decreasing the resist line width, or decreasing the dry etching resistance of the polymer, etc. Can get

Claims (6)

Alkaline catalyst was added to the polymer solution obtained by dissolving a styrene-based monomer containing at least 4-acetoxy styrene monomer and dimethyl-2,2-azobiscarboxylic acid ester in a solvent to polymerize a styrene-based monomer, followed by hydrolysis by washing with water. A method for producing a polymer compound for resist, characterized in that. The method of claim 1, A method for producing a polymer compound for resist, wherein the dimethyl-2,2-azobiscarboxylic acid ester is dimethyl-2,2-azobis (2-methylpropionate). The method of claim 1, The styrene monomer is represented by the following formula (1) (In formula, R <^1> represents a hydrogen atom, a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, or a C2-C7 acyloxy group, and R <^2> represents a hydrogen atom or a methyl group. The manufacturing method of the high molecular compound for resists represented by the following). The method of claim 1, A method for producing a polymer compound for resist, wherein the solvent does not contain methanol. The method according to claim 1, The said alkali catalyst is a manufacturing method of the high molecular compound for resists which are quaternary amine hydroxides. The method of claim 1, (2) (In formula, R <^3> represents a hydrogen atom or a methyl group, R <^4> is a C1-C6 alkyl group or any of following formula (3)-(7). A method for producing a high-molecular compound for a resist, wherein the compound represented by is copolymerized with a styrene monomer.