JPH07243761A - Method of refining resist constituent materials - Google Patents

Abstract

(57) [Summary] [Purpose] With regard to a method for purifying a resist constituent material, an object thereof is to put an efficient purification method into practical use. [Structure] Each material constituting the resist is made into a powder state by using a freeze-drying method, and the powder is washed with a poor solvent of the material to remove impurities contained in the material, and then dried. As a feature, a method for purifying a resist constituent material is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a resist constituent material. Because it is necessary to process a large amount of information at high speed,
The semiconductor device which constitutes the main body of the information processing device has been integrated and the LSI and VLSI have been put into practical use, but the integrated device has been further advanced and the ULSI has been put into practical use.

Here, a thin film forming technique, a photolithography technique (photolithography or electron beam lithography), an impurity ion implantation technique and the like are used for forming a semiconductor integrated circuit. The minimum line width of the fine pattern to be formed has been reduced to about 1/4 μm (Quarter-micron).

[0003]

2. Description of the Related Art In a resist used for forming a pattern by selectively etching a metal thin film or a dielectric thin film formed on a semiconductor substrate (wafer), an exposure position by ionizing radiation becomes soluble in a developing solution. There are a positive type and a negative type in which the exposure position becomes insoluble, and they are used properly depending on the application and resolution, but as the minimum line width formed by photo-etching technology becomes smaller, corrosion caused by the resist It has become more necessary than ever to eliminate this.

That is, when alkali ions (Na ⁺ ), (K ⁺ ), chlorine ions (Cl ⁻ ), calcium ions (Ca ⁺⁺ ) and the like exist in the resist, these ions are adsorbed on the metal thin film. Corrosion occurs, and when various metal ions are present, they infiltrate into the dielectric thin film and reduce its dielectric strength.

Therefore, it is necessary that such impurity ions do not exist in the resist, and for that purpose it is essential to use a highly pure material. Here, the resist has different composition between positive type and negative type, base resin, photosensitizer,
It is formed by selectively combining various materials such as a sensitizer, a crosslinking agent, a dissolution inhibitor, and a surfactant.

Therefore, although high-purity materials are obtained and used, the allowable impurity content is ppb (parts pe
Since it is less than (r billion), users often purify and use it.When the target is a high molecular substance, the reprecipitation method is used, and when it is a low molecular weight substance, the recrystallization method or the reprecipitation method is used. Further, the solvent is refined using a distillation method.

In the reprecipitation method, the target substance to be purified is once completely dissolved in a good solvent (solvent having a high solubility of the substance to be purified), and then filtered to remove insoluble impurities. next,
When this solution is dropped little by little into a poor solvent (a solvent in which the substance to be purified has low solubility), the good solvent diffuses into the poor solvent, and as a result, the substance to be purified precipitates as a powder, while the poor solvent Since the impurities dissolved in the solvent are still present in the poor solvent, the powdery substance to be purified is taken out by filtration.

[0008]

Most of the substances that form resists are polymeric substances such as base resins, and a reprecipitation method is used for this purification. It was uneconomical because a large amount of solvent was required to purify the product.

Particularly, in order to disperse the good solvent, it is necessary to use a large amount of the poor solvent. For example, reprecipitation of a few g of the polymer substance requires the use of 1 liter or more of the poor solvent, which is too small. And the good solvent does not disperse, so the polymer does not solidify.

Further, the good solvent also requires a certain amount or more, and even if a solution of a polymer substance is made with a small amount of the good solvent and dropped into a poor solvent, the viscosity of the solution is high, so that the good solvent is There is a tendency that it does not completely disperse in a poor solvent and becomes a paste or a microcapsule, and a good solvent and impurities are accumulated inside the capsule.

This problem can be solved by increasing the amount of the good solvent, but if the amount of the good solvent is increased, a large amount of the poor solvent is also required in proportion thereto. Here, the required amount of good solvent depends on the type of polymer material and cannot be generally stated. ”Polymers with strong polarities are strongly bound to the solvent and difficult to disperse in large amounts. A trend is seen to require a solvent.

[0012] As described above, the reprecipitation method of a polymer substance requires the use of a large amount of solvent, is uneconomical, and needs improvement.

[0013]

[Means for Solving the Problems] The above-mentioned problems are solved by subjecting each material constituting a resist to a powder state by using a freeze-drying method, and then washing this powder with a poor solvent for the polymer substance to form a substance. This can be solved by removing the impurities contained and then drying.

[0014]

According to the present invention, the polymer substance constituting the resist is powdered by the freeze-drying method, and the powder is washed with a poor solvent to remove impurities soluble in the poor solvent.

That is, since the powder obtained by the freeze-drying method is in a completely powder state, the poor solvent can spread to every corner of the polymer substance, so that the cleaning effect is high and the purification efficiency is excellent. .

Here, regarding the base resin, the photosensitizer, the sensitizer, the cross-linking agent, the dissolution inhibitor, and the surfactant constituting the resist, the polymer substances to which the present invention can be applied are as follows. Become. Base resin: cresol novolac, phenol novolac, polystyrene, polychloromethylstyrene, polyhydroxystyrene, polytertialbutoxycarbonyloxystyrene, polytetrahydropyranyloxystyrene, polymethacrylate, polytertiarybutylmethacrylate, linear siloxane, Ladder-type siloxane,
Linear type silphenylene siloxane, ladder type silphenylene siloxane, microgel type silphenylene siloxane, etc. Photosensitizer: diazoresin, cyclized polyisoprene, etc. Sensitizer: polymer containing quinone structure, polyvinyl ferrocene, etc. Crosslinking agent: acetylated Dissolution inhibitors such as polystyrene and epoxidized phenol novolac: Polytertiary butyl methacrylate,
Surfactants such as polytertialbutoxycarbonyloxystyrene, etc .: Sodium polyvinylbenzene sulfonate, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol, etc. The procedure for carrying out the present invention will be described below. The polymer substance to be purified is first dissolved in a solvent for freeze-drying. Here, it is common to use benzene for non-polar resins, 1,4-dioxane for polar resins, and water for water-soluble resins. Impurities insoluble in the solvent for freeze-drying are removed by filtration. Freeze-dry. The poor solvent is poured into a flask containing the powdery polymer substance obtained by freeze-drying, and shaken well to dissolve impurities soluble in the poor solvent. Filter to remove the poor solvent in which the impurities are dissolved, and repeat the steps from to as necessary. The polymeric material obtained by filtration is dried.

Here, the poor solvent is a solvent that does not dissolve the polymer substance to be purified, and although the solubility of the polymer substance is not clearly defined, it is 0 to 0.1 per 1 liter of the solvent. It is desirable that the amount is about g, and further, the range is 0 to 0.01 g. Further, in the resist according to the present invention, since removal of ionic impurities is important, polar solvents that dissolve ionic substances, specifically alcohols such as methanol, ethanol, and isopropyl alcohol, and water are suitable. Acetone, tetrahydrofuran, etc. are not suitable because they dissolve many resins.

[0018]

【Example】

Example 1 1 g of commercially available phenol novolac (weight average molecular weight 2000, manufactured by Sumitomo Bakelite) was added to 1,4-dioxane.
It was dissolved in 200 cc and filtered, and the filtrate was placed in a 500 cc eggplant-shaped flask and freeze-dried.

Next, 300 cc of pure water was poured into the phenol novolac placed in the flask, covered with a lid, vigorously shaken for 5 minutes, suction filtered with a glass filter, and dried overnight with a vacuum desiccator to remove water. .

On the other hand, as a comparison, 1 g of the same phenol novolac was dissolved in 200 cc of methanol and filtered to remove impurities, and then the filtrate was gradually dropped into 1 liter of pure water while stirring to precipitate. The precipitate was suction filtered with a glass filter and dried in a vacuum desiccator overnight to remove water.

Then, the impurity content was measured by performing atomic absorption spectrometry on the sample subjected to the purification method of the present invention and the conventional reprecipitation method and the sample before purification. Table 1 shows these results, and it can be seen that the purification method according to the present invention is very effective. Example 2: Polychloromethylstyrene obtained by radical polymerization of chloromethylstyrene (weight average molecular weight 400
(1) was dissolved in 200 cc of benzene and filtered, and the filtrate was placed in a 500 cc eggplant type flask and freeze-dried.

Next, 300 cc of ethanol was poured into the polychloromethylstyrene contained in the flask, covered with a lid, vigorously shaken for 5 minutes, suction filtered with a glass filter, and dried overnight in a vacuum desiccator.

On the other hand, as a comparison, 1 g of the same polychloromethylstyrene was dissolved in 200 cc of toluene, filtered to remove impurities, and then the filtrate was gradually added dropwise to 1 liter of hexane with stirring to cause precipitation. The precipitate was suction filtered with a glass filter and dried in a vacuum desiccator overnight.

Then, the impurities content was measured by performing atomic absorption spectrometry on the sample subjected to the purification method of the present invention and the conventional reprecipitation method and the sample before purification. Table 2 shows the results, and it can be seen that the purification method according to the present invention is very effective and can be applied to nonpolar polymers. Example 3: 1 g of ladder-type siloxane polymethylsilylsiloxane (abbreviated as PMSS, weight average molecular weight 50000, manufactured by Nippon Zeon) was dissolved in 200 cc of benzene and filtered, and the filtrate was placed in a 500 cc eggplant-shaped flask. It put and lyophilized.

Next, 300 cc was added to PMSS placed in the flask.
Pour in methanol, cover and shake vigorously for 5 minutes,
It was suction filtered with a glass filter and dried in a vacuum desiccator overnight.

On the other hand, as a comparison, 20 g of the same PMSS is used.
After dissolving in 0 cc of toluene and filtering to remove impurities, the filtrate was gradually dropped into 1 liter of hexane while stirring to precipitate, and the precipitate was suction filtered with a glass filter and washed with a vacuum desiccator. Dried overnight.

Then, the impurities content was measured by performing atomic absorption spectrometry on the sample subjected to the purification method of the present invention, the conventional reprecipitation method and the sample before purification. Table 3 shows the results, and it can be seen that the purification method according to the present invention is very effective and can be applied to silicone resins.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

According to the present invention, the material constituting the resist can be purified without using a large amount of solvent, and the use of this resist can improve the quality of the semiconductor integrated circuit. The material refining method can be widely applied not only for resists.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miwa Igarashi 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Ryoko Kuramitsu, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture Fujitsu Limited ( 72) Inventor Koji Nozaki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (4)

[Claims] 1. A resist-constituting material which comprises: powdering each material constituting a resist, washing with a poor solvent for the material to remove impurities contained in the material, and then drying. Purification method. 2. The refining of a resist constituent material according to claim 1, wherein the material is a base resin, a photosensitizer, a sensitizer, a cross-linking agent, a dissolution inhibitor and a surfactant constituting the resist. Method. 3. The method for purifying a resist constituent material according to claim 1, wherein the powder state is obtained by a freeze-drying method. 4. The method for purifying a resist constituent material according to claim 1, wherein the poor solvent is alcohol or water.