JPH0948623A - Quartz glass manufacturing method - Google Patents

Abstract

(57) Abstract: An object of the present invention is to produce a high-purity transparent quartz glass effective for a jig for semiconductor production, a liquid crystal substrate, etc., by using an amorphous silica powder suitable for press molding. I will provide a. SOLUTION: In the method for producing quartz glass by firing a press-molded body of silica powder, as silica powder,
The average particle size is in the range of 0.5 to 10 μm, and Na, K,
0.1 to 10% by weight of a water-soluble acrylic resin having a glass transition point of −50 ° C. to 0 ° C. is added to amorphous silica powder having Fe, Ti, and Al impurities of 1 ppm or less. Granulated powder is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for semiconductor manufacturing, and a method for manufacturing high-purity transparent quartz glass that can be used for liquid crystal substrates and the like.

[0002]

2. Description of the Related Art Conventionally, quartz glass is manufactured by a method in which natural quartz is used as a raw material by electric melting in a vacuum furnace or by Bernoulli melting with an oxyhydrogen flame.
Further, in recent years, a method of flame-hydrolyzing a synthetic raw material such as SiCl ₄ and depositing it as glass, and a method of once depositing it as a porous body and then vitrifying it by sintering have been industrialized.

Further, at the development stage, silica powder is molded by various wet molding methods or dry molding methods such as pressing, and is sintered to be vitrified.

[0004]

All of the manufacturing methods currently industrialized are methods for manufacturing a column or slab-shaped quartz glass ingot, and in order to give a desired shape, a machine such as cutting or grinding is used. Requires processing and melt processing.

On the other hand, in order to shorten the processing labor, a method of manufacturing silica glass by forming silica powder into a desired shape by various molding methods in advance and then firing the silica glass has been studied. In particular, dry press molding is performed. When used, there is a possibility that a plate-like shape can be manufactured with high surface accuracy. However, at present, it has not been industrialized due to various problems such as lamination and chipping of the press-molded body, cracks during firing, and large bubbles remaining in the manufactured quartz glass.

The present invention has been made for the purpose of solving these problems, and most of the conventional problems in the method of firing and vitrifying a press-molded article which is industrially advantageous are mostly the steps of the press-molding. The present invention has been made paying attention to the fact that the above problems can be solved by using a silica powder suitable for molding.

[0007]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, one of the features of the method for producing quartz glass of the present invention is a method for producing quartz glass by firing a press-molded body of silica powder, wherein the average particle size is in the range of 0.5 to 10 μm, and Na Of water-soluble acrylic resin having a glass transition point of −50 ° C. to 0 ° C. to an amorphous silica powder having impurities of K, Fe, Ti, and Al of 1 ppm or less.
The above-mentioned press-molded body is formed by using the granulated powder obtained by adding 10 wt.

In the above method, the glass transition point is -5.
Water-soluble acrylic resin having a temperature of 0 ° C to 0 ° C is added in an amount of 0.1 to 10
A water-soluble acryl which is obtained by heating the press-molded product at a temperature of 500 to 1300 ° C. when manufacturing the quartz glass by using the press-molded product formed by using the granulated powder which is added by weight% and granulated. After decomposing and removing the system resin, densification treatment is performed by heating and sintering at a temperature of 1300 to 1600 ° C in a vacuum atmosphere, and then heating and melting at a temperature of 1700 to 1850 ° C in an inert gas atmosphere of nitrogen gas or argon gas. It is preferable that the amorphous silica powder is allowed to cool and vitrify, and the amorphous silica powder used is preferably an amorphous silica powder obtained by reacting an aqueous alkali metal silicate solution with an acid.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The silica powder used in the present invention has an average particle size in the range of 0.5 to 10 μm and contains Na, K and F.
It is necessary to be a fine high-purity powder in which each impurity of e, Ti, and Al is 1 ppm or less. The reason that the average particle size is in the above range is to enable powder molding,
Press molding is impossible or difficult with silica powder having an average particle diameter outside this range. "Average particle size" here
Means an average value of particle diameters of primary particles measured by light scattering, for example, by sufficiently dispersing powder in a liquid, and does not target secondary particles obtained by a granulation operation.

Further, the contained Na, K, Fe, Ti,
It is necessary that each impurity of Al is 1 ppm or less, and if silica powder in which each of these impurities exceeds 1 ppm is used, the light transmittance in the ultraviolet region tends to decrease, and this high purity is used for semiconductor manufacturing. The use of transparent glass is not preferable because it causes a problem that the production cannot be appropriately performed. Such high-purity powder is usually
Obtained by a synthetic method. As a synthetic method, a method of obtaining silica by removing an alkali metal by reacting an alkali metal silicic acid aqueous solution (water glass) with an acid, SiCl ₄
There are a method of hydrolyzing silica to silica and a method of hydrolyzing silicon alkoxide to silica. For industrial scale production, alkali metal such as sodium, potassium and lithium and an alkali metal composed of silicon dioxide are used. Those obtained by a method of reacting an aqueous silicate solution (water glass) with an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid are suitable.

In the present invention, in order to improve press moldability, the amorphous silica powder contains 0.1 to 1 of a water-soluble acrylic resin having a glass transition point of -50 ° C to 0 ° C.
It is added so as to have a ratio of 0% by weight (in each case, a weight ratio in a dry state). A water-soluble acrylic resin is selected as an additive because it is necessary to disperse silica powder in water to form a slurry for granulation of the powder, and when the slurry is formed, the water-soluble acrylic resin is silica. This is because uniform mixing with the slurry is easy. Examples of such water-soluble acrylic resins include polyacrylic acid esters, polymethacrylic acid esters, polymers of methoxymethyl methacrylate and acrylic acid, and the like.

The glass transition point of the water-soluble acrylic resin added is set within the above range because the density of the press-formed product has a great influence on the properties of the finally obtained glass. To do. That is, when the compact density is low, a large number of large bubbles having a diameter of 100 μm or more are generated or the entire glass is greatly distorted, but such a phenomenon can be avoided by increasing the compact density. On the other hand, when a water-soluble acrylic resin having a glass transition point at room temperature or higher is added to silica powder, the occurrence of defects such as cracks can be suppressed as compared with the case of no addition,
Although it is possible to obtain a press-molded body with a high density,
It is not sufficient to suppress the occurrence of bubbles and deformation in the obtained glass. In the present invention, since a water-soluble acrylic resin having a glass transition point of -50 ° C to 0 ° C, which is sufficiently lower than room temperature, is used, the resin itself is largely plastically deformed, so that the density of the molded body is significantly improved. Good quality glass can be obtained by firing such a molded body. For these reasons, a water-soluble acrylic resin having a glass transition point in the above range is preferably used in the present invention.

If the amount added is more than 10% by weight, cracks may be generated in the molded product during heating for resin removal after press molding, or innumerable large bubbles may be generated in the obtained glass. On the other hand, the addition amount is 0.1% by weight
If it is less than the above range, the effect is insufficient, so the above range is set.

The slurry prepared by mixing the silica powder and the water-soluble acrylic resin is granulated into secondary particles by using a granulating device such as, but not limited to, a spray dryer. . The secondary particles are granulated in order to enhance the fluidity of the powder, for example, to facilitate the filling into a press molding die and to obtain a molded body having a higher density. In many cases, it is preferable that the particle diameter (secondary particle diameter) is generally 30 to 200 μm.

Granulated secondary particle powder (granulated powder)
Is filled in a molding die such as an appropriate die and molded into a press-molded body having a predetermined shape. Molding pressure is limited by what is though not generally 200~2000kg / cm ^2, preferably from being a 500~1000kg / cm ² approximately.

The molded product is 500 to 1300 after press molding.
The resin is removed by heating at 0 ° C. to remove the contained acrylic resin. The atmosphere during this resin removal treatment is preferably atmospheric air. When the acrylic resin remains in the molded product after firing, carbon content remains in the finally obtained glass and appears as black spots, which causes bubbles to be generated, so that the resin removal treatment is necessary and sufficient. Desirably, in the above temperature range, usually 2 to 20 hours, preferably 5 to 1
Hold for 0 hours.

The heat treatment for vitrifying the resin-removed molded product is carried out by placing the molded product on a carbon flat plate having a high degree of flatness. From room temperature to 1300 to 1600 ℃
To densify by heating in a vacuum atmosphere until the temperature is increased to 1700 to 1850 ° C. in an inert gas atmosphere of nitrogen gas or argon gas to melt and densify the compacted body and hold for a certain period of time. After that, the target transparent quartz glass can be obtained by allowing to cool. The heat treatment for densification is preferably performed at 1300 to 1600 ° C. for 1 to 5 hours. Further, the heat treatment for melting is preferably held at 1700 to 1850 ° C. for preferably 30 minutes or less, more preferably 5 to 20 minutes.
This melting temperature range is defined by the fact that below 1700 ° C., cracks due to crystallization often occur, while
This is because at a temperature higher than 850 ° C., the viscosity in the molten state is greatly reduced, and it becomes difficult to obtain glass having a desired shape.

[0019]

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Amorphous silica powder (trade name Silica Ace A, manufactured by Nitto Kagaku Kogyo Co., Ltd.) was prepared by reacting sodium silicate with an acid and then heat-treating and pulverizing the mixture to prepare an average particle size of 1.6 μm. Impurity analysis results are shown in Table 1 below) was dispersed in water to prepare a 50 wt% slurry.

[0021]

[Table 1]

To this slurry, an aqueous solution of an acrylic copolymer resin having a glass transition point of -8 ° C. (manufactured by Chuo Rika Kogyo, trade name Ricabond SA-200) was added, and the acrylic copolymer resin was contained in silica powder in an amount of 2% by weight (dry). (Weight ratio: same below) Added so that it was included, and stirred sufficiently.

After stirring, granulation was performed using a spray dryer (average granulated particle size: 70 μm) to obtain a secondary powder (granulated powder) for press molding. This powder was filled in a mold, and a pressure of 500 kg / cm ² was applied by a uniaxial press machine to
A compact having a size of 00 × 200 × 1.5 mm (thickness) was obtained. When the molded product was visually observed, no cracks were found in the peripheral portion.

This molded body was kept at 1050 ° C. for 10 hours in the atmosphere to remove the acrylic copolymer resin in the molded body. The density of the molded product after resin removal is 1.35 g / cm.
^{Was 3} . This is a carbon flat plate (225 x 225 x 5
mm (thickness: manufactured by Toyo Tanso Co., Ltd., manufactured by E252), placed in an electric furnace, and heated to 1450 ° C. in vacuum at 100 ° C./h.
After the temperature was raised at r and held for 5 hours, the inside of the furnace was made into a nitrogen gas atmosphere, the temperature was raised to 1800 ° C. at 300 ° C./hr, and the temperature was held for 5 minutes to obtain quartz glass.

The obtained glass (size: 180 × 180
Table 2 shows the results of measuring the flatness and the thickness unevenness for x1.25 mm (thickness).

[0026]

[Table 2]

The flatness referred to here is the surface roughness,
It is expressed by three amounts: warpage and undulation. Warpage is a large periodic deformation that appears once or twice in a glass plate, undulation is irregularity with a period shorter than warpage, and surface roughness is a period shorter than undulation. Surface irregularities, whose values are defined by the difference between the maximum and minimum heights within one period. The thickness unevenness is defined as the difference between the maximum value and the minimum value when the thickness is measured at five or more designated points on the glass plate. In addition, the impurities in the glass were analyzed and the results shown in Table 3 were obtained. In addition, when the bubbles were visually inspected, only one bubble having a diameter of 100 μm was observed.

[0028]

[Table 3]

Example 2 Amorphous silica powder having an average particle size of 5 μm prepared in the same manner as in Example 1 (trade name: silica ace A, manufactured by Nitto Chemical Industry, analysis results of contained impurities are shown in Table 1 below). The same operation as in Example 1 was performed to obtain a secondary powder (granulated particle size: 150 μm) for press molding containing 2% by weight of the acrylic copolymer resin used in Example 1. This powder was filled in a mold, and a pressure of 500 kg / cm ² was applied with a uniaxial press to obtain a compact having a size of 200 × 200 × 1.5 mm (thickness). When the molded product was visually observed, no cracks were found in the peripheral portion.

The molded body was kept at 1050 ° C. for 10 hours in the atmosphere to remove the acrylic copolymer resin in the molded body. The density of the molded body after the resin removal is 1.32 g / cm ^3.
Met.

Next, this molded body was subjected to the same operations as in Example 1 to obtain quartz glass. Resulting glass (size: 1
Table 2 shows the results of measuring the flatness and the thickness unevenness for 80 × 180 × 1.25 mm (thickness). In addition, the impurities in the glass were analyzed and the results shown in Table 3 were obtained.

Further, when the bubbles were visually inspected, it was found to be 150
Only one bubble having a diameter of μm was observed.

Example 3 The secondary powder for press molding prepared in Example 1 was filled in a mold and a pressure of 500 kg / cm ² was applied by a uniaxial press machine, and the molded body was taken out from the mold. Further, this molded body is loaded into a rubber bag, and 2000
A pressure of kg / cm ² is applied, and 200 × 200 × 10.
A molded body having a size of 0 mm (thickness) was obtained. When the molded product was visually observed, no cracks were found in the peripheral portion.

The molded body was kept at 1050 ° C. for 10 hours in the atmosphere to remove the acrylic copolymer resin in the molded body. The density of the molded body after the resin removal is 1.40 g / cm ³
Met.

The same operation as in Example 1 was carried out to obtain quartz glass. The resulting glass (size 183 x 183 x
Table 2 shows the results of measuring the flatness and the thickness unevenness for 8.30 mm (thickness). In addition, the impurities in the glass were analyzed and the results shown in Table 3 were obtained. Further, when the bubbles were visually inspected, only one bubble having a diameter of 50 μm was observed.

Comparative Example 1 The same amorphous silica powder as in Example 1 was dispersed in water, and 5
A 0 wt% slurry was prepared. To this slurry, an acrylic copolymer resin aqueous solution having a glass transition point of 17 ° C. (Chuo Rika Kogyo, trade name Ricabond SA-203) was added so that the acrylic copolymer resin was contained in the silica powder in an amount of 2% by weight when dried. And stirred well. After stirring,
Granulate using a spray dryer (average granulated particle size:
70 μm) to obtain a secondary powder for press molding. This powder was filled in a mold, and a pressure of 500 kg / cm ² was applied by a uniaxial press machine to obtain 200 × 200 × 1.5 mm (thickness).
A molded body having a size of This molded body was exposed to air at 105
It was kept at 0 ° C. for 10 hours to remove the acrylic copolymer resin in the molded body. The molded product density after resin removal is 1.15.
It was g / cm ³ .

The same operation as in Example 1 was carried out to obtain quartz glass. Obtained glass (size: 180 x 180
Table 2 shows the results of measuring the flatness and the thickness unevenness for x1.25 mm (thickness). In addition, when visually inspecting bubbles, 500 bubbles having a diameter of 100 μm or more were observed.

Comparative Example 2 The same amorphous silica powder as in Example 1 was dispersed in water, and
A 0 wt% slurry was prepared. This slurry was granulated using a spray dryer (average granulated particle size: 70μ
m), a secondary powder for press molding was obtained. This powder was filled in a mold, and a pressure of 500 kg / cm ² was applied with a uniaxial press to obtain a compact having a size of 200 × 200 × 1.5 mm (thickness). Many fine cracks were generated in the peripheral portion of the obtained molded body. This molded body was exposed to the air 1
It was kept at 050 ° C for 10 hours. The compact density after firing was 1.12 g / cm ³ .

The same operation as in Example 1 was carried out to obtain quartz glass. Obtained glass (size: 180 x 180
Table 2 shows the results of measuring the flatness and the thickness unevenness for x1.25 mm (thickness). In addition, when visually inspecting bubbles, 600 bubbles having a diameter of 100 μm or more were observed.

Example 4 Ten glass plates each obtained in Examples 1 and 2 were polished to produce a substrate glass having a thickness of 1.1 mm. The obtained substrate glass has a surface roughness of 0.005 μm and a waviness of 13 μ.
m and the thickness unevenness was 50 μm. Comparative Example 1 for comparison
And, when the glass plate according to Comparative Example 2 was polished to the same surface accuracy, about twice as many polishing steps were required.

[0041]

As described above, according to the manufacturing method of the present invention, it is possible to manufacture a transparent quartz glass having an extremely small amount of bubbles and a small amount of deformation by using the press molding method which is advantageous in industrial production. Is obtained.

Therefore, it is possible to inexpensively provide a transparent quartz glass which can be used as a constituent material of various semiconductor manufacturing jigs, a substrate for liquid crystal display such as a polysilicon TFT or a color filter, and a photomask.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukinobu Hara 3-1-1, Koyo, Hachinohe City, Aomori Nitto Chemical Industry Co., Ltd. (72) Inventor Yuya Nagata 1-18-7 Fujisaki, Tsuchiura City, Ibaraki Prefecture (72) ) Inventor Masayuki Kudo 447-22 Tsukisato, Edozaki-cho, Inashiki-gun, Ibaraki Prefecture (72) Inventor Kenji Kamo 2-17 Amakubo, Tsukuba City, Ibaraki Prefecture 4-17 (72) Toshihiko Okamura 2 Amakubo, Tsukuba City, Ibaraki Prefecture 4-17 (72) Inventor Koji Tsukuma 1-18-7-901 Fujisaki, Tsuchiura City, Ibaraki Prefecture (72) Inventor Kazuichi Sudo 2-7 Tokamachi, Yamagata City Yamagata Prefecture Yoshikazu Kikuchi Sagae Yamagata Prefecture 43-7 Tsuruta, Sagae City

Claims (3)

[Claims] 1. A method for producing quartz glass by firing a press-molded body of silica powder, wherein the average particle size is 0.5 to 0.5.
Within the range of 10 μm, and Na, K, Fe, Ti, A
0.1 to 10% by weight of a water-soluble acrylic resin having a glass transition point of −50 ° C. to 0 ° C. was added to 1 part of an amorphous silica powder having impurities of 1 ppm or less, and granulated by granulation. A method for producing quartz glass, characterized in that the press-formed product is formed using granular powder. 2. The water-soluble composition as set forth in claim 1, wherein the press-formed product formed from granulated powder containing 0.1 to 10% by weight of a water-soluble acrylic resin is heated at a temperature of 500 to 1300 ° C. After decomposing and removing the water-soluble acrylic resin, densification treatment is performed by heating and sintering at a temperature of 1300 to 1600 ° C in a vacuum atmosphere, and then heating at a temperature of 1700 to 1850 ° C in an inert gas atmosphere of nitrogen gas or argon gas. A method for producing quartz glass, which comprises melting and then allowing to cool and vitrify. 3. The production of quartz glass according to claim 1, wherein the amorphous silica powder is an amorphous silica powder obtained by reacting an aqueous alkali metal silicate solution with an acid. Method.