JPH0761827A - Opaque quartz glass - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an opaque quartz glass having high heat resistance and excellent heat shielding and infrared scattering properties. [Structure] An opaque quartz glass having a specific gravity of 2.08 to 2.18 and containing bubbles having the following physical properties. (1) Bubble diameter is 10 to 160 μm (2) Bubble density is 100,000 to 600,000 /
cm ³ (3) Total volume of bubbles in opaque quartz glass is 3 to 1
0% (4) Total bubble cross-sectional area per 100 cm ^{3 of} opaque quartz glass is 800 to 1,500 cm ² .

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can efficiently produce an opaque quartz glass having a high purity, a high heat resistance and an excellent heat shielding property, particularly an opaque quartz glass plate as an infrared scattering and heat shielding material for a heat treatment furnace. It relates to a solid opaque quartz glass block.

[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 it has 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 JP-A-5-900, 100,000 bubbles / cm ³ or less of bubbles Or 6000 pieces / cm at both ends of the boat for forming a furnace core tube with opaque quartz glass containing slag, or for mounting a semiconductor wafer as described in Japanese Utility Model Laid-Open No. 1-262234.
An opaque quartz glass heat ray scattering plate containing bubbles of less than ³ was provided.

However, in recent years, vertical heat treatment furnaces have become the mainstream of heat treatment furnaces for the semiconductor industry. In this vertical heat treatment furnace, the lower end portion of the furnace is placed on a metal frame and the joining portion thereof is used. Irregular scattering of heat rays occurs, or because the cooling unit provided to protect the seal member that seals the joint between the lower end and the metal frame disturbs the temperature inside the furnace, The temperature distribution in the furnace was not uniform, and it was usual to install heat ray scattering and heat shield plates. Opaque quartz glass has been preferably used as the heat ray scattering and heat shielding material because of its good heat resistance and heat shielding properties. However, the conventional opaque quartz glass plate has a large amount of deformation at a high temperature, and in particular, undergoes a large thermal deformation during the heat treatment of a silicon wafer heated to about 1000 ° C. or more, and has a sufficient function as a heat shield and an infrared scattering material. However, the life of the heat treatment furnace was short.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, the thermal deformation of the opaque quartz glass plate at a high temperature is caused by the volume of bubbles occupying the quartz glass substrate. Although it is related to the size and the heat resistance of the quartz glass, the diameter of the bubbles is reduced, but the density is increased to increase the total bubble cross-sectional area per unit volume of the opaque quartz glass and the total amount of the bubbles occupies in the opaque quartz glass. The present invention has been completed by finding that the heat deformation is reduced when the volume is reduced and the heat resistance is also improved when the concentration of sodium, potassium and OH groups in the opaque quartz glass is within a specific range.

It is an object of the present invention to provide a high-purity opaque quartz glass having a small bubble diameter but a high density and uniformly dispersed.

Another object of the present invention is to provide a high-purity opaque quartz glass heat shield material having high heat resistance and excellent heat shield properties.

[0007]

The present invention for achieving the above object relates to an opaque quartz glass characterized by containing bubbles having a specific gravity of 2.08 to 2.18 and the following physical properties. (1) Bubble diameter is 10 to 160 μm (2) Bubble density is 100,000 to 600,000 /
cm ³ (3) Total volume of bubbles in opaque quartz glass is 3 to 1
0% (4) Total bubble cross-sectional area per 100 cm ^{3 of} opaque quartz glass is 800-1,500 cm ^2.

The total bubble cross-sectional area per 100 cm ^{3 of the} opaque quartz glass is in accordance with DIN 58927. A thin piece of opaque quartz glass of a certain volume is photographed by transmitted light, and the total cross-sectional area of the bubbles contained is 100 cm ³ It is converted to the total cross-sectional area per hit.

The bubble density is the same as that described above, in which the number of bubbles is counted, and the number is counted as 1 cm ³ of opaque quartz glass.
It is the number converted to.

The opaque quartz glass in the present invention means an 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 and high-purity amorphous quartz powder are used as raw materials for producing the opaque quartz glass. Particularly, high-purity crystal powder having a concentration of sodium and potassium of 0.2 ppm or less among alkali metal elements or high-purity crystal powder is chemically purified as described in US Pat. No. 4,983,370, and sodium and potassium. The concentration of 0.
The crystal powder is preferably 2 ppm or less, and the synthetic quartz glass obtained by the soot method is preferably amorphous silica powder having a sodium and potassium concentration of 0.2 ppm or less and a particle size adjusted to 110 to 350 μm. In addition to the content of the alkali metal element, it is preferable that the lithium concentration is 1.0 ppm or less in order to improve heat resistance.

Further, for the vitrification of the above glass raw material powder, an electric melting method, which is a method for producing quartz glass having a low OH group content, is adopted. In particular, by setting the OH group concentration to 10 ppm or less, it is possible to prevent the viscosity of the silica glass from decreasing at high temperatures due to the OH groups.

The thermal conductivity of quartz glass is 1000 ° C.
It is said that radiant heat conduction becomes dominant in the above cases. When the bubbles are present in the quartz glass, the radiation at the above-mentioned temperature is not limited to the reflection on the glass surface but also occurs inside the bubbles. As described above, the surface area and the distribution of bubbles in opaque quartz glass have a great influence on the reflection and transmission of radiant heat rays. Therefore, opaque quartz glass is used as a heat shield and infrared scattering material for heat treatment furnaces such as silicon wafers. It is necessary to increase the total bubble cross-sectional area of the quartz glass and to uniformly disperse the bubbles.

By the way, in order to increase the total cross-sectional area of the bubbles, it is sufficient to disperse the large bubbles uniformly in the opaque quartz glass. However, according to the study by the present inventors, the shielding made of the opaque quartz glass having the large bubbles is used. It has been found that heat and infrared scattering materials have a large thermal deformation at high temperatures.
Since the thermal deformation at high temperature increases as the total volume occupied by the bubbles contained in the opaque quartz glass increases, the inventors of the present invention reduce the volume of the bubbles and increase the bubble density to reduce the total volume of the bubbles. An experiment was conducted based on the idea that the area would be large.
When the density is 0 μm and the density is 100,000 to 600,000 cells / cm ³ , the total bubble cross-sectional area per 100 cm ^{3 of} opaque quartz glass is 800 to 1500 cm ² , and the total volume of bubbles is 5 to 10%. Regardless, the heat shield property was significantly 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.
I needed to set it to 8.

In the opaque quartz glass of the present invention, for example, high-purity quartz is put in a heat-resistant forming die and melted or vitrified while the temperature rising speed is controlled or raw powder is filled in the heat-resistant die. Is carried out by a specific laminating method, and it is subjected to molten vitrification. The opaque quartz glass block obtained by these manufacturing methods is cut into a plate of about 5 mm to 1 cm to prepare a heat shielding and infrared scattering material.

The present invention will be described in more detail below. The crystal powders used below are raw crystal powder, crystal powder A from which particles with a particle size of 250 μm or more have been removed, and crystal powder from which particles with a particle size of 180 μm or more have been removed. B, and their particle size distribution (meaning the weight ratio of the mesh openings remaining on the sieve shown in the particle size column in the table when the used crystal powder was sieved)
Is shown in Table 1.

[0016]

[Table 1] Note) In the table, the values are% by weight.

[0017]

Example 1 Quartz powder A was placed in an electric furnace using a quartz glass tube as a furnace core tube, and hydrogen chloride / nitrogen was mixed at a ratio of 50:50 to 120.
The heat treatment was performed at 0 ° C. for 1 hour to purify the alkali metal. This purified crystal powder A is 200 mm in diameter x 200 in height
A high-purity graphite container (mm) was filled to a depth of 100 mm, placed in a vacuum furnace, and evacuated to 10 ^-2 torr or less to remove air remaining between particles. Then, the inside of the furnace is vacuum-disrupted with nitrogen, and the temperature is increased from room temperature to 1200 ° C at 20 ° C / while flowing nitrogen at a flow rate of 5 l / min.
Min 1200 ° C to 1630 ° C 6.14 ° C / min,
The temperature was raised from 1630 to 1750 ° C. at a rate of 0.34 ° C./min and kept at 1750 ° C. for 50 minutes. When vitrified, the furnace was de-energized and naturally cooled. A sample was cut out from the obtained opaque quartz glass block, and specific heat, thermal conductivity, bubble density, bubble volume, bubble cross-sectional area, specific gravity, apparent viscosity and bubble distribution were measured for this sample. The former two measurement results are shown in Tables 2 and 3, the cell volume, the cell density, the cell cross-sectional area, the specific gravity and the apparent viscosity are shown in Table 4, and the cell distribution is shown in Table 5.

The specific gravity is measured by the Archimedes method,
The apparent viscosity was calculated from the amount of deformation when a sample was cut into a strip of 3 × 1 × 50 mm and held at 1260 ° C. for 10 hours by the beam bending method (two-point support, no load).

[0019]

[Table 2] Note: In the table, specific heat is measured by the adiabatic continuous method and thermal diffusivity is measured by
The flash method was used.

[0020]

[Table 3] Note) In the table, the thermal conductivity was calculated by the hot wire method.

As is clear from Tables 2 and 3 above, Example 1
It can be seen that the opaque quartz glass of No. 2 has low heat conductivity and excellent heat insulating property.

[0022]

[Example 2] Crystal powder B was subjected to alkali metal element removal treatment under the same conditions as in Example 1, and then vitrified in the same manner as in Example 1 while controlling the melting temperature to give an opaque quartz glass block. Obtained. A sample was cut out from the opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.

[0023]

[Comparative Example 1] The particle size of the raw material crystal powder was not adjusted, and the alkali metal element was removed under the same conditions as in Example 1 and then charged in a graphite container. A glass block was manufactured. A sample was cut out from the obtained opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.

[0024]

[Comparative Example 2] Quartz powder A, which had been treated to remove alkali metal elements, was directly filled in a graphite mold without adjusting the particle size, and melted and vitrified under the same conditions as in Example 1 to obtain an opaque quartz glass. A sample was prepared from the opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.

[0025]

Comparative Example 3 Crystalline powder A was subjected to alkali removal treatment, then rotationally molded, and heated and melted with an arc flame from the inside in an air atmosphere to produce an opaque quartz glass glock.
A sample was cut out from the opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.

[0026]

Comparative Example 4 The raw material crystal powder was sieved, only the crystal powder having a particle size of 103 μm or less was selected, treated with alkali in the same manner as in Example 1, and then heated and melted to produce an opaque quartz glass. A sample was cut out from the opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.
Shown in.

[0027]

[Table 4]

[0028]

[Table 5]

As shown in Tables 4 and 5 above, the opaque quartz glass obtained by subjecting the crystal powder having the maximum particle size adjusted in the range of 110 μm or more to 250 μm or less to the alkali removal treatment is not adjusted in particle size. The bubble volume is almost the same as that of the opaque quartz glass of Comparative Example 2 which is not subjected to alkali removal treatment, but the bubble density and the quartz glass are 100 cm.
^It can be seen that the total bubble cross-sectional area per ³ is large and the heat shield effect is large.

Further, as shown in Table 5, the bubbles in the opaque quartz glass obtained by using the quartz powder having the particle size distribution within the range of the present invention are finer and more uniform in distribution than the bubbles of the comparative example. As is clear from Comparative Example 4, there is little decrease in viscosity at high temperature.

Table 6 shows the alkali metal element concentration and the OH group concentration in the opaque quartz glass of each of the above Examples and Comparative Examples 1 to 3. As is clear from the table, the opaque quartz glass having an alkali metal element concentration and an OH group concentration within the ranges specified in the present invention has a high viscosity at high temperatures,
Excellent heat resistance. Further, the infrared transmittances of the opaque quartz glass of the present invention and the opaque quartz glasses of Comparative Examples 1 and 3 are shown in FIG. 1. As shown in the figure, the opaque quartz glass of the present invention has a low infrared transmittance and has a heat shielding property. It turns out that it is excellent.

[0032]

[Table 6]

[0033]

EFFECTS OF THE INVENTION The opaque quartz glass of the present invention has a large cell density and a large total cell cross-sectional area per 100 cm ^{3 of} quartz glass, and the cells having a small diameter are uniformly dispersed. The apparent viscosity (log η at 1260 ° C.) ) Is also 12.
It is an opaque quartz glass with a high porosity of 50 poise or more and excellent heat resistance, infrared scattering and heat shielding properties. Therefore, the heat shield made of the opaque quartz glass of the present invention does not undergo thermal deformation even in the heat treatment exceeding 1000 ° C. like the heat treatment of the silicon wafer, and retains sufficient infrared scattering and heat shield properties. it can.

[Brief description of drawings]

FIG. 1 shows the infrared transmittance of the opaque quartz glass of the present invention.

[Procedure amendment]

[Submission date] September 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014] The opaque silica glass of the present invention, for example, putting a high-purity quartz heat resistance of the mold, while controlling the Atsushi Nobori speed, filling of the raw material powder into either the molten vitrified, or a heat resistant type Is carried out by a specific laminating method, and it is subjected to molten vitrification. The opaque quartz glass block obtained by these manufacturing methods is cut into a plate of about 5 mm to 1 cm to prepare a heat shielding and infrared scattering material.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

Comparative Example 4 The raw material crystal powder was sieved, only the crystal powder having a particle size of 103 μm or less was selected, treated with alkali in the same manner as in Example 1, and then heated and melted to produce an opaque quartz glass. A sample was cut out from the opaque quartz glass block, and the bubble density, bubble volume, bubble cross-sectional area, apparent viscosity and bubble distribution were measured. The results are shown in Tables 4 and 5.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[0027]

[Table 4]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

[0028]

[Table 5]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kimura 2-13-13, Kitafu, Takefu City, Fukui Prefecture Shin-Etsu Quartz Co., Ltd. Takefu Factory

Claims (3)

[Claims] 1. An opaque quartz glass having a specific gravity of 2.08 to 2.18 and containing bubbles having the following physical properties. (1) Bubble diameter is 10 to 160 μm (2) Bubble density is 100,000 to 600,000 /
cm ³ (3) Total volume of bubbles in opaque quartz glass is 3 to 1
0% (4) Total bubble cross-sectional area per 100 cm ^{3 of} opaque quartz glass is 800-1,500 cm ^2. 2. The concentration of sodium and potassium contained in the opaque quartz glass is 0.2 ppm or less, respectively.
The opaque quartz glass according to claim 1, wherein the H group concentration is 10 ppm or less. 3. An infrared scattering and heat shielding opaque quartz glass plate obtained by cutting out the opaque quartz glass according to claim 1.