JP3213384B2 - Manufacturing method of quartz glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing quartz glass used in, for example, a semiconductor process.

[0002]

2. Description of the Related Art A quartz glass tool used in a semiconductor process, for example, is generally manufactured as follows.

(1) A material having a simple shape such as a tube or a plate is made.

(2) A material is welded or machined to obtain a target shape.

However, in the case of a tool having a relatively simple shape,
Direct molding methods have also been put to practical use. For example, a single crystal pulling crucible is directly processed into a crucible by arc melting a raw material powder.

In recent years, a sol-gel method has attracted attention as a method for producing quartz glass by direct molding, and has been developed. In the sol-gel method, the drying step and the baking step are very difficult. These processes have the drawback that it takes time and the yield is poor. Various improvements have been proposed to eliminate such disadvantages.

[0007]

In the above-mentioned general manufacturing method, processing is time-consuming, requires skill, and is wasteful in material.

[0008] Further, in the production by the above-mentioned direct molding method, there is a problem that a large amount of impurities are likely to be mixed.

Further, in the above-mentioned sol-gel method, a simple shape is mainly used, and it is difficult to apply to a tool having a large and complicated shape.

The present invention provides a method for producing quartz glass, which can produce, for example, a tool for a large-scale semiconductor process, which is becoming increasingly pure and complicated in recent years, with high material yield and high purity in a short time. The purpose is to:

[0011]

SUMMARY OF THE INVENTION The present invention provides a silicate ester
Water, water adjusted to pH 3 or less, and a water-soluble boiling point 1
Making a first mixture of an organic solvent at 20 ° C. or higher,
The first mixture is mixed with an average particle size of 10 μm or more and 100 μm or less.
Mixed with amorphous or amorphous silica to form a slurry
Make a mixture, and place the slurry-like second mixture in a mold.
Gel in a mold to form a desired shape
After the molded product is released from the mold, it is heated.
And a method for producing quartz glass .

EXAMPLE In the method for producing quartz glass of the present invention, first, crystalline or amorphous silica having an average particle size of 1 μm to 500 μm, preferably 10 μm to 100 μm is used as a starting material.

If the average particle size is smaller than 1 μm, the pore diameter of the molded product becomes small, so that bubbles are difficult to be removed during calcination, which is not suitable. On the other hand, when the average particle diameter is larger than 500 μm, the average pore diameter becomes large, and it becomes difficult to pour the slurry into the mold.

As a binder, silicate ester, pH 3
A first mixture comprising water adjusted as described below and an organic solvent soluble in water and having a boiling point of 120 ° C. or higher was prepared to prepare a silica powder 100
A total of 30 to 100 parts by weight of the first mixture is mixed with parts by weight of the first mixture to form a second mixture, which is used as a slurry. This second mixture is also called a mixed dispersion medium or a dispersion medium.

Since the silicate ester and water are not directly mixed (they become a homogeneous solution after hydrolysis), a solvent for mixing them, for example, an alcohol, may be added as appropriate.

The amount of the second mixture (mixed dispersion medium) added to 100 parts by weight of the silica powder is preferably 30 to 100 parts by weight. If the second mixture (mixed dispersion medium) is less than 30 parts by weight, mixing becomes difficult, and if it is more than 100 parts by weight, the density of the molded article tends to be low.

The silicate ester is not particularly limited, but is preferably an easily available one such as ethyl silicate or methyl silicate. The addition amount of the silicate ester varies depending on the particle size of the silica particles. When fine particles are used, it is better to increase the addition amount.

Water is added to adjust the pH to 3 or less with an acid to hydrolyze the silicate ester. The acid at this time is not particularly limited, either. For example, an acid which volatilizes during heating and hardly remains such as hydrochloric acid, nitric acid and acetic acid is preferable.

The amount of water to be added is preferably not less than the hydrolysis equivalent of the silicate ester and not more than 30 times the hydrolysis equivalent. If the water is less than the hydrolysis equivalent of the silicate ester, the hydrolysis will not proceed sufficiently, and if it is more than 30 times, the gelation will be slow,
In addition, handling becomes difficult because the strength of the gel is reduced.

The organic solvent is soluble in water and is present in the molded product even after the evaporation of water or alcohol, which is a hydrolysis product of ethyl silicate, to prevent liquid evaporation during temperature rise. It has the role of preventing associated cracks. Since the boiling point of the alcohol produced from the silicate ester which is generally available is lower than the boiling point of water, the boiling point of the organic solvent to be used may be higher than 100 ° C. (1 atm). Organic solvents having a boiling point of 120 ° C. or higher are preferred. Two or more organic solvents may be used.

Although an example in which all are mixed at the time of hydrolysis has been described, all may be mixed before the hydrolyzed silicate ester gels, and the mixing procedure is not particularly limited.

The gelation time can be shortened by adjusting the pH of the slurry after the hydrolysis to 3.5 to 5.5. If the pH of the slurry is less than 3.5, the gelation time is too slow to be practical. Slurry pH
When is high, the gel time is faster. At pH = 3.5 (20 ° C.), it is about 30 hours (h), which is a practical range, though it depends on the composition. On the other hand, if the pH is higher than 5.5, the gelation time becomes very short,
Work becomes difficult.

The aqueous base solution used for adjusting the pH is preferably a base which volatilizes during heating and hardly remains, and an organic base such as ammonia is preferred. NaOH, KOH and the like are unsuitable.

The slurry thus prepared is poured into a mold, left standing in a closed state, and gels in the mold. The gel time varies depending on the pH of the slurry.

Since the gel shrinks with time, it is preferable to release the gel after gelation. It is preferable that at least only the mold part in the contraction direction be released.

Further, since the gel immediately after gelation has a low strength, at least 3
It is preferable to leave or keep it over time. However,
There is no problem with the degree of exposure to the release atmosphere in a short time at the time of mold release, but it is better that this time is as short as possible. Further, by increasing the temperature at this time, the strength developing time can be shortened. At this time, it is preferable to prevent volatilization from the molded product, and it is preferable to place the molded product in a pressure-resistant container that can withstand the vapor pressure at that temperature.

In the state of the molded body, processing such as hole processing and diameter adjustment can be easily performed using a cutting tool made of quartz glass.
More preferably, two or more parts can be combined into one molded body.

The molded body obtained by combining a plurality of parts in this way is heated and sintered to form a quartz glass product. At this time, a drying step of the molded body is not particularly required, and the molding is sent to a heating step. This is a point greatly different from the usual sol-gel method that requires a long time for drying.

Although the heating temperature varies depending on the particle size of the silica powder, the transparent body is obtained at 1400 ° C. to 1850 ° C.
Further, although different depending on the particle size, a porous body can be obtained by keeping the heating temperature lower than the temperature at which a transparent body is obtained.

The heating rate is relatively low up to the boiling point of the organic solvent mixed at the time of preparing the slurry, that is, 200 ° C. /
h or less, preferably 100 ° C./h, and thereafter, 1000 ° C./h or less, preferably 600 ° C./h or less. If the temperature is raised at a rate higher than 1000 ° C./h, cracks occur in the molded body due to rapid volatilization of the solvent, and swelling occurs in the fired body due to rapid closed pore formation.

Further, the above-mentioned transparency temperature of 1400 ° C.
Although it may be heated up to 1850 ° C, depending on the particle size, it is calcined at 1200 ° C to 1600 ° C,
A method of heating to a clarifying temperature of 1400 ° C. to 1850 ° C. can also be used.

In calcination, deformation can be prevented and high purity can be maintained by using coarse crystalline silica powder as a filling powder.

Further, even in this calcined state, processing such as hole drilling and diameter adjustment can be easily performed using a quartz glass cutting tool. Furthermore, two or more components can be combined into one calcined body. Further, after calcination, two or more molded bodies can be combined into one molded body and then fired.

In the final firing after the calcination, a low OH quartz glass product can be obtained by reducing the atmosphere. When the sintering treatment is performed in a Cl ₂ -containing atmosphere, a quartz glass product having very few metal impurities can be obtained.

Hereinafter, preferred examples and comparative examples of the present invention will be described.

Example 1 25 parts by weight of ethyl silicate, 20 parts by weight of 0.01 N hydrochloric acid and 5 parts by weight of ethylene glycol were added to 100 parts by weight of quartz powder having an average particle diameter of 30 μm, and the mixture was stirred for 1 hour to form a slurry.

On the other hand, the mold shown in FIG. 1 was used. This type is
An outer mold 1 and inner dies 2 and 3 are provided. The above-mentioned slurry was poured into the gap 4 of the mold having this shape, sealed, and held.

After 5 days, the slurry gelled, and the molded product was released from the mold, sealed and maintained for 10 hours.

Thereafter, it was placed in an electric furnace and heated to 400 ° C. at a heating rate of 100 ° C./h, thereafter heated at a heating rate of 600 ° C./h and heated at 1850 ° C. for 30 minutes. . Then, a transparent quartz glass was obtained.

Example 2 A trial production was performed under the same conditions as in Example 1 except that the particle size of the raw materials was changed. Table 1 shows the results. The yield indicated the ratio of the number of non-defective products in 20 pieces. Table 1 shows the effect of the raw material particle size.

As is clear from Table 1, in the examples of the present invention, the yield was good in both the forming step and the firing step. However, in Comparative Examples having an average particle size of more than 500 μm, the moldability was poor, and the yield in the molding step was 0%, which was inappropriate. In Comparative Examples smaller than 1 μm, bubbles or cracks were generated during firing, and the yield in the firing step was low or 0%, which was inappropriate.

[0042]

[Table 1] Example 3 A trial production was performed under the same conditions as in Example 1 except that only the organic solvent to be added was changed. Table 2 shows the results. Yield is 20
The number of non-defective products in each item is shown. Table 2 shows the effect of the added organic solvent.

As shown in Table 2, in all of the examples of the present invention, the calcination yield was good. However, the comparative examples of 1-propanol having a boiling point of an organic solvent of 120 ° C. or less,
In the comparative example of butanol, cracking occurred during firing, and the firing yield was poor, which was unsuitable.

[0044]

[Table 2] Example 4 A prototype was produced under the same conditions as in Example 1 except that the amount of the dispersion medium added to the quartz powder was changed. Table 3 shows the results. The composition ratio of the added dispersion medium is 25: 2 by weight ratio of ethyl silicate: 0.01N hydrochloric acid: ethylene glycol.
0: 5. The yield indicated the ratio of the number of non-defective products in 20 pieces. Table 3 shows the effect of the ratio of the added dispersion medium.

In such a composition ratio, silica 10
When the amount of the dispersion medium is 30 to 100 parts by weight with respect to 0 parts by weight, when the amount is less than 30 parts by weight, molding becomes difficult, and the molding yield is 0%. On the other hand, when the amount is more than 100 parts by weight, the proportion of the powder becomes low, the handling of the molded body becomes difficult, cracks occur at the time of firing, the firing yield is 0%, and good products cannot be obtained.

[0046]

[Table 3] Example 5 A prototype was produced under the same conditions as in Example 1 except that the time during which the molded body was kept in a closed state after release was changed. The results are shown in Table 4. The yield indicated the ratio of the number of non-defective products in 20 pieces. Table 4
Shows the effect of the retention time after gelation (at 25 ° C.).

Under these conditions, the holding time is preferably 3 hours or more. If the holding time is shorter than 3 hours, cracks tend to occur during firing and the firing yield is poor.

[0048]

[Table 4] Here, the holding time is a time obtained by subtracting the gel time from the time when the molded body is put into the open atmosphere. The gel time is a time at which the slurry does not flow even when the slurry is tilted.
The holding time in Example 1 is 5 hours (h).

Example 6 25 parts by weight of ethyl silicate, 20 parts by weight of 0.01 N hydrochloric acid and 5 parts by weight of ethylene glycol were added to 100 parts by weight of quartz glass powder having an average particle diameter of 30 μm, and the mixture was stirred for 1 hour to form a slurry.

On the other hand, the slurry was poured into the gap 4 using a mold having a shape as shown in FIG. 1, sealed, and held.

After 5 days, the molded product was gelled, and the molded product was released from the mold, sealed and kept for 10 hours.

Thereafter, the compact was placed in an electric furnace and heated at 400 ° C.
The temperature was increased at a rate of 100 ° C./h until the temperature was increased at a rate of 600 ° C./h and heated at 1850 ° C. for 30 minutes to obtain a transparent quartz glass.

[0053]Example 7  A molded product was produced in the same manner as in Example 6. This molded body
A 25 mm diameter through-hole was drilled from the side of. This
An outer diameter of 25 mm and an inner diameter of 20 m produced by the same method
m, a 200 mm long tubular molded body was fitted.

Thereafter, the compact was placed in an electric furnace,
The temperature was raised to 0 ° C. at a rate of 100 ° C./h, and thereafter, the temperature was raised at a rate of 600 ° C./h and heated at 1850 ° C. for 30 minutes. Then, a transparent quartz glass was obtained.

Example 8 A calcined body was produced in the same manner as in Example 6. A side surface of the calcined body was penetrated by a drill, and a through hole having a diameter of 25 mm was formed. Here, an outer diameter of 25 mm and an inner diameter of 2
A tubular calcined body of 0 mm and length of 200 mm was fitted.

Thereafter, the compact was placed in an electric furnace, and
Heated at 50 ° C. for 30 minutes. Then, a transparent quartz glass was obtained.

Example 9 25 parts by weight of ethyl silicate, 20 parts by weight of 0.01 N hydrochloric acid and 5 parts by weight of ethylene glycol were added to 100 parts by weight of quartz powder having an average particle diameter of 30 μm, and the mixture was stirred for 1 hour. Then 1
% Ammonia water was added to adjust the pH to 4.2 to obtain a slurry.

On the other hand, the slurry was poured into the gap 4 using a mold having the shape shown in FIG. 1, sealed, and held.

After 5 hours, the gel was gelled. The molded product was released from the mold, sealed and kept for 10 hours.

Thereafter, the molded body was placed in an electric furnace and heated at 400 ° C.
Temperature at a heating rate of 100 ° C./h until
The temperature was raised at a rate of 1 ° C./h, followed by heating at 1850 ° C. for 30 minutes. Then, a transparent quartz glass was obtained.

Example 10 A molded product was produced in the same manner as in Example 7.

The molded body was placed in an electric furnace, and
Calcination was performed at 4 ° C. for 4 hours (heating time: 4 hours). The calcined body was placed in a vacuum firing furnace, and was heated in an atmosphere of N ₂ 0.5 torr for 18 hours.
Heated at 50 ° C. for 30 minutes. Then, a transparent quartz glass was obtained.

Example 11 A molded product was produced in the same manner as in Example 7.

The compact was placed in an electric furnace, and
Calcination was performed at 4 ° C. for 4 hours (heating time: 4 hours). Place the calcined body in a vacuum furnace at 1400 ° C. for 1 hour, 5% Cl ₂ /95% He
After performing the treatment described above, in an atmosphere of N ₂ 0.5 torr,
Heated at 1850 ° C. for 30 minutes. Then, a transparent quartz glass was obtained.

The present invention is not limited to the embodiment described above.

[0066]

According to the method of the present invention, quartz glass, such as a tool material for a large semiconductor process, can be manufactured with a high purity in a very short time. Therefore, manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a mold for forming a slurry used when producing the quartz glass of the present invention.

[Explanation of symbols]

 1 outer mold 2 inner mold 3 inner mold 4 gap ◆

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Takahashi 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. (56) References JP-A-2-141432 (JP, A) JP-A-2- 38321 (JP, A) JP-A-3-109220 (JP, A) JP-A-61-183129 (JP, A) JP-A-61-256928 (JP, A) JP-A-1-179730 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 8/02

Claims (1)

(57) [Claims] 1. A silicate ester adjusted to pH 3 or less.
From water and water-soluble organic solvents with a boiling point of 120 ° C or higher
A first mixture having a mean particle size of 10
Crystalline or amorphous silica with a size of μm to 100 μm
To form a second mixture in the form of a slurry,
Put the second mixture in a mold into a mold and allow it to gel in the mold.
The molded body was formed by molding the shape of
And then heating the quartz glass
Law.