JP3050353B2 - Method for producing opaque 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 opaque quartz glass having high purity, high heat resistance, and excellent heat shielding properties, and particularly to a solid opaque quartz glass block useful as a heat shielding material for a heat treatment furnace. .

[0002]

2. Description of the Related Art Conventionally, quartz glass has been used as a heat treatment furnace or a heat treatment jig for the semiconductor industry because of its high purity and excellent heat resistance. In this heat treatment furnace for the semiconductor industry, it is important to make the temperature distribution in the furnace uniform, and for that purpose, as shown in Japanese Patent Application Laid-Open No. 5-900, 100,000 bubbles / cm ³ or less. A core tube is made of opaque quartz glass containing 6000 or 6000 pieces / cm at both ends of a boat for mounting semiconductor wafers as described in Japanese Utility Model Application Laid-Open No. 1-162234.
A heat-scattering plate of opaque quartz glass containing less than ³ bubbles was provided.

Opaque quartz glass has been suitably used as the heat-scattering plate material because of its excellent heat resistance and heat-shielding properties. This was a general manufacturing method. And the opaque quartz glass block,
After filling glass raw material powder, especially quartz powder into the heat resistant mold,
It was manufactured by heating and melting in an electric furnace (hereinafter referred to as a filling-type melting method).

However, in the above-mentioned conventional filling type melting method, glass raw material powder having a particle size range of 350 to 50 μm is generally used, and this is melted to produce opaque quartz glass. Bubbles in the glass have a maximum diameter of 22 as shown in Japanese Utility Model Laid-Open No. 1-162234.
It was as large as 0 μm, and the bubble density was less than 100,000 cells / cm ³ . Even if this heat ray scattering plate made of opaque quartz glass is used as a heat ray scattering and heat shield plate of a vertical heat treatment furnace, which has recently become the mainstream of heat treatment furnaces for the semiconductor industry, the lower end of the vertical heat treatment furnace and the metal It was not possible to sufficiently prevent irregular scattering of heat rays at the joint of the gantry and disturbance in the furnace temperature due to the cooling unit provided for protecting the seal member. In addition, in the above-mentioned conventional filling-type melting method, large cavities and the like are easily generated in the center of the opaque quartz glass block, and it is difficult to manufacture a block in which uniform bubbles are distributed throughout. It was not satisfactory as a quartz glass block for use.

[0005]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have set the maximum particle size of the glass raw material powder to be 250 μm or less, By controlling the temperature rise rate, the diameter of bubbles can be reduced and the number of bubbles can be increased, and the bubbles can be evenly dispersed throughout the block. Have been obtained, and the present invention has been completed.

An object of the present invention is to provide a method for producing a high-purity opaque quartz glass in which bubbles have a small diameter but a high density and are uniformly dispersed.

An object of the present invention is to provide a method for producing a high-purity opaque quartz glass heat insulating material having high heat resistance and excellent heat insulating properties.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for producing an opaque quartz glass containing fine bubbles by heating and melting a glass raw material powder layer filled in a heat resistant mold. A glass raw material powder having a maximum particle size of 250 μm or less is filled in a mold, and the glass raw material powder layer is heated from room temperature to a melting temperature of the glass raw material powder while controlling a temperature rising rate in an inert gas atmosphere. Then 1
Hold in a temperature range of 740 to 1800 ° C. for 10 minutes or more,
The present invention relates to a method for producing opaque quartz glass, which is characterized by being melted and vitrified.

The opaque quartz glass is opaque quartz glass containing fine bubbles obtained by heating and melting glass raw material powder in a non-oxidizing atmosphere. High-purity crystalline quartz powder is used as a raw material for producing this opaque quartz glass. In particular, the concentration of sodium and potassium among the alkali metal elements is preferably 0.2 ppm or less from the viewpoint of the heat resistance of the opaque quartz glass, that is, the reduction of thermal deformation at high temperatures. The quartz powder having a concentration of sodium and potassium is, for example, U.S. Pat.
No. 983,370, which is obtained by subjecting a high-purity quartz powder to a purification treatment at a temperature of 1100 to 1300 ° C. in a mixed gas atmosphere of chlorine and / or hydrogen chloride and nitrogen gas.

[0010] In addition, for the vitrification of glass raw material powder,
An electromelting method, which is a method for producing quartz glass having a small OH group content, is employed. By employing this method, the OH group concentration in the opaque quartz glass can be reduced to 10 ppm or less, and the heat resistance at high temperatures can be improved.

By the way, it is said that radiant heat conduction becomes dominant when the temperature reaches 1000 ° C. or higher. When bubbles exist in the quartz glass at the above temperature, the reflection of the heat rays occurs not only on the surface of the glass but also in the bubbles inside, so that the surface area and distribution of the bubbles in the opaque quartz glass greatly affect the reflection and transmission of the heat rays. Exert. Therefore, in order to use opaque quartz glass as a heat shield and infrared scattering material for heat treatment furnaces, it is necessary to increase the total surface area of bubbles contained per unit volume, increase the number of bubbles, and disperse the bubbles uniformly. It is important.

In order to increase the total surface area of the bubbles contained per unit volume and increase the number of bubbles, according to an experiment conducted by the present inventors, glass raw material powder was sieved to have a maximum particle size of 250 μm. It is preferable to remove the above particles or use a glass raw material powder containing no particles of 250 μm or more in advance. By using the glass raw material powder having this particle size, the maximum diameter of bubbles can be reduced to 160 μm or less, the bubble density can be increased to 100,000 / cm ³ or more, and the heat shielding property and the heat ray scattering property are remarkably improved. At this time, the density of the opaque quartz glass is set to 2.08 to 2.1 in order to minimize the deformation due to its own weight.
Had to be 8.

Here, the maximum particle size of the glass raw material powder is 250
The term “μm or less” refers to a state in which no particles remain on the sieve when sieving is performed using a sieve having an opening of 250 μm.

Further, in the opaque quartz glass block obtained by the conventional filling-type melting method, a large cavity or the like in the center is generated, and it is difficult to obtain a quartz glass block having uniform bubbles. According to this, the heat conduction of the glass raw material powder layer is extremely small, and if the heating rate during melting is too high, the unmelted layer remains inside the opaque quartz glass block even if the outside is in a molten state as shown in FIG. 5 remains, which becomes a large void, and conversely, if the heating rate is too slow,
As shown in FIG. 3, it was found that a layer having many air bubbles 4 was formed on the surface layer of the opaque quartz glass block, and a translucent layer 6 having large but few air bubbles was formed at the bottom. Therefore, when heating was performed while controlling the temperature rising rate during melting of the glass raw material powder, the distribution of the bubbles 4 became uniform as shown in FIG. 1B, and high heat shielding properties were obtained over the entire block. In particular, an opaque quartz glass block in which fine bubbles having a maximum diameter of 160 μm or less and a bubble density of 100,000 / cm ³ or more were uniformly dispersed throughout the whole was obtained by controlling the heating rate to the following range. . Room temperature ≦ T ≦ 1200 ° C. 10 to 50 ° C./min 1200 ° C.∠T ≦ 1700 ° C. 1 to 10 ° C./min. 1700 ° C.∠T ≦ 1800 ° C. 5 ° C./min or less

After heating at the above heating rate, 1740 to 1
By holding in a temperature range of 800 ° C. for 10 minutes or more,
Uniform melt vitrification of the glass raw material powder can be ensured.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. The physical properties of the following Examples and Comparative Examples are values based on the following measurement methods.

Measurement of physical property values: Measurement of total cross-sectional area of bubbles: A flake of opaque quartz glass having a fixed volume was photographed with transmitted light in accordance with DIN 58927, and the cross-sectional area of the contained bubbles was totaled to obtain a volume of 100 cm.
Measured by converting to the total cross-sectional area per ³・ Bubble density measurement: Count the number of bubbles by the same method as above and convert the number to 1 cm ³ of opaque quartz glass ・ Measure specific gravity: Measured by Archimedes method

[0018]

Example 1 High-purity raw material quartz powder was sieved to remove particles of 250 μm or more as shown in Table 1.

[0019]

[Table 1]

The above-mentioned sieved quartz powder was placed in an electric furnace using a quartz glass tube as a furnace core tube and heat-treated at 1200 ° C. for 1 hour at 50:50 hydrogen chloride / nitrogen to purify the alkali metal. . This purified sieve fraction quartz powder 1
× 200 mm high-purity graphite mold 1 with a depth of 10
Filled to 0 mm, placed in a vacuum furnace, 10 ^-2 t
Air was evacuated to orr or lower to remove air remaining between the particles. Next, the inside of the furnace is vacuum-ruptured with nitrogen, and while flowing nitrogen at a flow rate of 5 l / min, the temperature is increased from room temperature to 1200 ° C. at 20 ° C./min and from 1200 ° C. to 1630 ° C.
14 ° C / min, 0.34 ° C from 1630 to 1750 ° C
/ Min, and maintained at 1750 ° C. for 50 minutes. At the time of vitrification, the power supply to the furnace was stopped and the furnace was naturally cooled.
A sample was cut out from the obtained opaque quartz glass block 3 and the bubble density, the total cross-sectional area, the specific gravity and the bubble distribution were measured. The results are shown in Tables 2 and 3.

[0021]

Comparative Example 1 The raw material quartz powder was not subjected to particle size adjustment, and the alkali metal element was removed under the same conditions as in Example 1 and then filled in a graphite mold. Glass block 3 was manufactured. A sample was cut out from the obtained opaque quartz glass block, and physical properties were measured in the same manner as in Example 1. Tables 2 and 3 show the results.
Shown in

[0022]

[Table 2]

[0023]

[Table 3]

As shown in Table 2 above, the opaque quartz glass obtained by the method of the present invention has no significant difference in the bubble volume as compared with Comparative Example 1 in which the particle size is not adjusted, but the bubble density and the total cross-sectional area It is a transparent quartz glass having a large heat dissipation effect as shown in Table 3, in which fine bubbles are uniformly distributed.

[0025]

[Comparative Example 2] A sieved crystal powder 1 was filled in a high-purity graphite mold 2 similar to that in Example 1, and it was placed in a vacuum furnace.
The atmosphere in the furnace was replaced with nitrogen in the same atmosphere,
The temperature was raised at 20 ° C./min to 20 ° C. and from 830 ° C. to 1750 ° C. at 8 ° C./min, and maintained at 1750 ° C. for 50 minutes. When the obtained opaque quartz glass block was vertically divided and examined, an unmelted layer 5 was found inside the block, and bubbles were unevenly present.

[0026]

Comparative Example 3 A sieved crystal powder filled in a graphite mold under the same conditions as in Comparative Example 2 was heated from room temperature to 1200 ° C. at 20 ° C.
The temperature was raised from 1200 to 1750 ° C at a rate of 0.34 ° C / min and maintained at 1750 ° C for 50 minutes. As shown in FIG. 3, in the obtained opaque quartz glass block, a large number of fine bubbles were present at the top, while a small number of large bubbles were present at the bottom, and a bubble distribution was observed. Is.

[0027]

According to the present invention, as described above, it is possible to produce an opaque quartz glass block in which uniform and fine bubbles are dispersed at a high density, and the heat insulating material cut out of the block makes the temperature distribution in the furnace uniform. It was effective to do.

[Brief description of the drawings]

FIG. 1 shows the manufacturing method of the present invention. FIG. 2 is a sectional view of an opaque quartz glass block obtained by a conventional filling-type melting method. FIG. 3 shows a cross-sectional view of an opaque quartz glass block obtained by overheating by a conventional filling type melting method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass raw material powder 2 Heat resistant type 3 Opaque quartz glass 4 Bubbles 5 Unmelted layer 6 Translucent layer

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Kimura 2-13-60 Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsu Quartz Co., Ltd. Inside the Takefu Plant (56) References JP-A-5-345636 (JP, A) JP-A-6-24771 (JP, A) JP-A-7-61838 (JP, A) JP-A-7-61839 (JP, A) JP-A-7-69674 (JP, A) (58) Int.Cl. ⁷ , DB name) C03C 1/00-14/00 C03B 20/00

Claims (3)

(57) [Claims] 1. A method for producing an opaque quartz glass containing fine bubbles by heating and melting a glass raw material powder layer filled in a heat-resistant mold, wherein the maximum diameter is 250 μm in the heat-resistant mold.
m, and then heating the glass material powder layer from room temperature to the melting temperature of the glass material powder while controlling the rate of temperature rise in an inert gas atmosphere. A method for producing opaque quartz glass, wherein the glass is melted while being kept in a temperature range of 10 ° C. for 10 minutes or more. 2. The method for producing opaque quartz glass according to claim 1, wherein the rate of temperature rise (T) is in the following range. Room temperature ≦ T ≦ 1200 ° C. 10 to 50 ° C./min 1200 ° C.∠T ≦ 1700 ° C. 1 to 10 ° C./min. 1700 ° C.∠T ≦ 1800 ° C. 5 ° C./min or less 3. The glass raw material powder has a sodium and potassium concentration of 0.2 ppm or less and an OH group concentration of 10 pp.
2. The method for producing opaque quartz glass according to claim 1, wherein m is equal to or less than m.