JPH07300341A - Opaque silica glass and its production - Google Patents

Abstract

PURPOSE:To obtain an opaque silica glass high in heat resistance and excellent in both heat-screening ability and infrared ray scattering ability. CONSTITUTION:This highly-pure opaque silica glass having the following opaque characteristics: cell diameter: 10-160mum; cell density: 100000-600000 counts/cm<3>; total cell volume: 3-10vol.% (closed cells); nitrogen element level in the silica glass base: 50-500ppm; and specific gravity: 2.08-2.18. This silica glass is obtained by ammoniating in an ammonia atmosphere at 600-1300 deg.C crystalline silica powder 0.01-100m<2>/g in specific surface area followed by heating in a molten state the resultant ammoniated silica powder in an inert gas atmosphere at 1600-2000 deg.C.

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. Regarding opaque quartz glass.

[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. However, in this vertical heat treatment furnace, the lower end portion of the furnace is placed on a metal pedestal. Irregular scattering of heat rays occurs at the joint, or the cooling unit provided to protect the seal member that seals the joint between the lower end and the metal frame disturbs the furnace temperature. Then
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 low viscosity at a high temperature and undergoes a thermal deformation during a high temperature treatment, particularly a large thermal deformation during a heat treatment of a silicon wafer which is heated to about 1000 ° C. or more. However, the life of the heat treatment furnace was short.

In addition, highly active gases such as oxygen, hydrogen, and ammonia remain in the bubbles of conventional opaque quartz glass, which are released during high-temperature processing and adversely affect semiconductor products to be processed. was there.

[0005]

Therefore, as a result of intensive studies by the present inventors to solve the above-mentioned drawbacks of the opaque quartz glass, the closed cells in the opaque quartz glass fall within a specific range. By adding nitrogen to the opaque quartz glass and substituting the active gas with the nitrogen gas, it is possible to improve the heat-shielding property and the high temperature viscosity, and it is possible to suppress the adverse effect of the active gas on the semiconductor product, The present invention has been completed. Ie

An object of the present invention is to provide a high-purity opaque quartz glass which has a high temperature viscosity and a small amount of residual active gas.

Another object of the present invention is to provide a high-purity opaque quartz glass having a high heat resistance and an excellent heat shielding property.

A further object of the present invention is to provide a method for producing the above high-purity opaque quartz glass.

[0009]

The present invention which achieves the above object has a specific gravity of 2.08 to 2.18, a bubble diameter of 10 to 160 μm, and a bubble density of 100,000 to 60.
The number of closed cells is 10,000 cells / cm ³ , the total volume of bubbles is 3 to 10%, and the nitrogen element concentration in the quartz glass substrate is 5
The present invention relates to a high-purity opaque quartz glass having 0 to 500 ppm, and 90% or more of gas in bubbles is nitrogen gas, and a manufacturing method thereof.

The opaque quartz glass is an opaque quartz glass containing fine bubbles. In the opaque quartz glass of the present invention, the fine bubbles have a bubble diameter of 10 to 1.
60 μm, total bubble volume 3 to 10%, bubble density 100,0
Comprised of 00 to 600,000 closed cells / cm ³ ,
Opaque quartz glass in which the closed cells are uniformly dispersed. And its specific gravity is 2.08, which is not deformed by its own weight.
The range is from ˜2.18. In the opaque quartz glass of the present invention, the closed cells are uniformly dispersed and the cell density is high as described above,
The total bubble cross-sectional area is 100 cm opaque quartz glass
^It is as large as 800 to 1,500 cm ² per ³ and has excellent heat insulation and heat shielding properties. Further, the opaque quartz glass of the present invention has a nitrogen element concentration in the range of 50 ppm to 600 ppm, and the contained nitrogen has a stronger Si than Si--O bond.
-N bond is generated and high temperature viscosity is high. For example, the viscosity at 1,260 ° C. is 10 ^12.8 poise, and the viscosity of opaque quartz glass produced from natural crystalline quartz powder is 10 ^12.2 poise or more. Further, the presence of NH group based on the contained nitrogen causes absorption of 3,400 cm ⁻¹ wavelength, improves absorption of infrared rays, and reduces heat ray transmittance. When the nitrogen content is less than 50 ppm, the viscosity at high temperature is not improved, and when the content exceeds 500 ppm, nitrogen is released during use, which is not preferable.

In addition to the above, 9
Since 0% or more is replaced with nitrogen gas, no active gas is generated which adversely affects the yield and performance of semiconductors even at high temperature heat treatment.

When the opaque quartz glass of the present invention is used as a semiconductor heat treatment jig, the concentration of alkali metal elements such as Na and K is 0.2 ppm or less, the concentration of Fe element is 0.1 ppm or less, and the concentration of Mg element is Mg. It is preferable that the Zr element concentration is 0.05 ppm or less and the Zr element concentration is 0.1 ppm or less.
The lower the concentration of each element is, the better, but excessive purification raises the cost rapidly, so it should be kept within a commercially viable range.

The method for producing the opaque quartz glass of the present invention is as follows. That is, according to the purification method described in, for example, U.S. Pat. No. 4,983,370, natural crystalline quartz powder is used in which the concentration of each alkali metal element of Na and K is 0.2 ppm or less and the concentration of Fe element is 0. 1 ppm or less, Mg element concentration is 0.05 ppm or less, Zr element concentration is 0.1 ppm or less, OH group concentration is 50 to 100 pp
m, a specific surface area of 0.01 m / g or more, and then the purified quartz powder was treated at 600 ° C. to 1,30 under an ammonia atmosphere as described in JP-A-5-345636.
It is heated to 0 ° C. to be ammoniated, and then it is charged into a carbon mold, and the temperature is 1,600 to 2,0 in an inert gas atmosphere.
The production method comprises heating and melting at a temperature of 00 ° C, preferably 1,600 to 1,800 ° C.

In the above-mentioned production method, when the specific surface area of the quartz powder is in the range of 0.01 to 100 m ² / g, the ammonia is favorably carried out. At this time, the OH group concentration is preferably 50 to 100 ppm. As a result, the nitrogen element concentration in the opaque quartz glass is 50 to 500 ppm, O
The H group concentration can be 10 ppm or less.

When the treatment temperature is set to 600 ° C. or lower in the above-mentioned ammoniating treatment, the reaction rate becomes too low and OH groups remain. Further, when the treatment temperature exceeds 1,300 ° C., the ammonia- or nitrogen-containing gas bound by the substitution reaction is released again, the final contained nitrogen is reduced, and heat resistance is not improved. The preferred reaction temperature is 800 ° C to 1.0
The temperature is 00 ° C, and the treatment is performed at this temperature for 1 to 5 hours.

The heating and melting of the quartz powder in the present invention is carried out in an inert gas atmosphere at a temperature range of 1,600 to 2,000 ° C., preferably 1,700 to 1,800 ° C.
By performing in this temperature range, ammonia or nitrogen gas is liberated from the ammonified quartz powder, and the quartz glass is foamed, and a part of it reacts with the opaque quartz glass to generate Si—N bond or NH group, and Oxygen, hydrogen, ammonia gas, etc., which are the active gases in the bubbles, are replaced with nitrogen gas, and 90% or more of the gas in the bubbles becomes nitrogen gas. When the heating and melting are performed in an atmosphere other than an inert gas atmosphere, the generation of fine closed cells is not observed, and when the melting temperature is less than 1,600 ° C., the melting of the quartz powder cannot be sufficiently obtained, The body cracks. On the other hand, when the melting temperature exceeds 2,000 ° C., the melting proceeds excessively and is softened, and the bubbles in the glass body are communicated with each other, so that the bubbles are less independent. As the heating and melting furnace, an electric melting furnace in which OH group is less mixed, for example, a resistance heating type decompression electric furnace having a heat-resistant type or heat-resistant case made of high-purity carbon, silicon carbide, silicon nitride or the like is preferable.

[0017]

EXAMPLES The present invention will be described in detail below with reference to specific examples. The raw material powders used in each example have particle size distributions shown in Table 1 (when the used quartz powder is sieved, mesh openings are shown in the table). (Refers to the weight ratio remaining on the sieve shown in the particle size column of 1.) and has the purity shown in Table 2.

[0018]

[Table 1] Note) Crystal powder A is crystal powder from which particles with a particle size of more than 180 μm have been removed.

[0019]

[Table 2]

The numerical values in the following examples are values measured by the following measuring method. (I) Specific heat; value measured by adiabatic continuous method. (Ii) Thermal diffusivity; value measured by laser flash method. (Iii) Thermal conductivity; value measured by the hot wire method. (Iv) Total cross-sectional area of air bubbles: According to DIN 58927, a thin piece of opaque quartz glass with a fixed volume is photographed with transmitted light,
A value obtained by totalizing the cross-sectional areas of the bubbles contained and converting it into the total cross-sectional area per 100 cm ^{3 of} volume. (V) Bubble density: The number of bubbles is counted by the same method as the method for measuring the total cross-sectional area of bubbles, and the number is counted as 1 cm ³ of opaque quartz glass.
The value converted to. (Vi) Specific gravity; value measured by Archimedes method. (Vii) Apparent viscosity: A value calculated from the amount of deformation when a sample was cut into a strip shape of 3 × 1 × 50 mm and held at 1,260 ° C. for 10 hours by a beam bending method (two-point support, no load). . (Viii) Nitrogen element concentration; value measured by inert gas melting conductivity method. (Ix) OH group concentration; value measured by diffuse reflection spectrum method by FT-IR. (X) Amount of gas in bubbles: A value obtained by destroying the obtained opaque quartz glass piece and measuring gas emitted from the bubbles by gas chromatograph mass spectrometry.

Example 1 Natural quartz crystal powder A having a specific surface area of 0.1 m ² / g was placed in an electric furnace using a quartz glass tube as a furnace core tube, and hydrogen chloride / nitrogen was 50:50 to 1,200. Heat treatment was carried out at 1 ° C. for 1 hour to purify the alkali metal and each element of iron, magnesium and zirconium. This purified crystal powder A was put into the furnace core tube again, and treated at 900 ° C. for 3 hours in an atmosphere having an ammonia / nitrogen ratio of 50:50 to perform ammonialation. This ammoniated crystal powder is placed in a high-purity graphite container having an inner diameter of 200 mmφ and a height of 200 mm and a depth of 200 mm.
Up to 10 ^-2 Torr
The air was evacuated below to remove the air remaining between the particles, and then the furnace was evacuated to vacuum with nitrogen and the temperature was raised from room temperature to 1200 ° C. at 20 ° C. while flowing at a flow rate of 5 l / min.
C / min, from 1200 to 1630 ° C 6.14
° C / min, from 1,630 to 1,750 ° C 0.34 ° C
The temperature was raised at a rate of / min and the temperature was maintained at 1,750 ° C. for 50 minutes for vitrification. When vitrified, the furnace was de-energized and naturally cooled. A sample was cut out from the obtained opaque quartz glass block, and for this sample, the thermal diffusivity,
Specific heat, thermal conductivity, bubble density, bubble volume, bubble cross-sectional area, specific gravity, apparent viscosity, nitrogen concentration, OH group concentration, bubble distribution, gas component analysis in bubbles and transmittance in the infrared region were measured.
Thermal diffusivity, specific heat, and thermal conductivity are shown in Table 3, bubble density,
Bubble volume, bubble cross-sectional area, specific gravity, apparent viscosity The nitrogen element concentration and the OH group concentration are shown in Table 4, the bubble distribution is shown in Table 5, and the gas component analysis in the bubble is shown in Table 6. Further, the transmittance in the infrared region is shown in FIG. As is clear from the figure, the infrared transmittance of the opaque quartz glass of the present invention is low,
Excellent heat shield.

[0022]

[Table 3]

Comparative Example 1 The raw material crystal powder was not subjected to particle size adjustment, the alkali metal element was removed under the same conditions as in Example 1, and then filled in a graphite container, and then opaque in the same manner as in Example 1. A quartz glass block was manufactured. A sample was cut out from the obtained opaque quartz glass block, and its bubble density, bubble volume, bubble cross-sectional area, and apparent viscosity were measured in the same manner as in Example 1.
The nitrogen element concentration, the OH group concentration, the bubble distribution, and the components in the bubbles were measured. The results are shown in Tables 4 and 5. In addition, the transmittance in the infrared region was investigated and shown in FIG. As is clear from the figure, no decrease in infrared transmittance was observed.

Comparative Example 2 Quartz powder A, which had been subjected to the alkali metal element removal treatment, was directly charged into a graphite mold 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, nitrogen element concentration, OH group concentration, bubble distribution, and bubble internal component were measured in the same manner as in Example 1. The results are shown in Tables 4 and 5. In addition, the transmittance in the infrared region was investigated and shown in FIG. As is clear from the figure, no decrease in infrared transmittance was observed.

[0025]

[Table 4]

[0026]

[Table 5]

As is apparent from Table 3 above, the opaque quartz glass of the present invention has low heat conductivity and excellent heat insulating properties, and crystal powder adjusted to have a maximum particle size in the range of 103 μm to 212 μm is alkali-removed. Compared with the opaque quartz glass of Comparative Example 1 in which the grain size was not adjusted, and Comparative Example 2 in which ammonia treatment was not performed even if the grain size was adjusted, the bubble volume was approximately the same, but the bubble density and the opaque quartz glass per 100 cm ³ It can be seen that the total cross-sectional area of the bubbles is large, the heat shielding effect is large, the high temperature viscosity is high, and the heat resistance is excellent.

Furthermore, as shown in Table 5, the opaque quartz glass of the present invention has a more uniform bubble distribution than the opaque quartz glass of the comparative example.

The opaque quartz glass pieces of each of the above-mentioned Example 1 and Comparative Examples 1 and 2 were destroyed, and the gas generated from the bubbles was analyzed by a gas chromatograph mass spectrometer. Most of the gas in the bubbles was replaced with nitrogen.

[0030]

[Table 6]

[0031]

EFFECTS OF THE INVENTION The opaque quartz glass of the present invention has a large cell density, a large total cell cross-sectional area, and evenly dispersed small cells, and its apparent viscosity at 1,260 ° C. is 12.8 poise or more. It is a high opaque quartz glass with excellent heat resistance, infrared scattering and heat shielding. A heat shield made of this opaque quartz glass does not undergo thermal deformation even when it is heat-treated at over 1,000 ° C. like the heat treatment of a silicon wafer, and retains sufficient infrared scattering and heat-shielding properties. .

[Brief description of drawings]

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

Claims (4)

[Claims] 1. Nitrogen element in a quartz glass substrate, having closed cells having a cell diameter of 10 to 160 μm, a cell density of 100,000 to 600,000 cells / cm ³ , and a total cell volume of 3 to 10%. The concentration is 50 to 500 ppm and the specific gravity is 2.
Opaque quartz glass characterized in that it is 08 to 2.18. 2. The concentration of each of sodium and potassium elements contained in the opaque quartz glass is 0.2 ppm or less, the OH group concentration is 10 ppm or less, and the iron element concentration is 0.1.
ppm, magnesium element concentration is 0.05 ppm or less,
Zirconium element concentration is 0.1 ppm or less, and 3,
The high-purity opaque quartz glass according to claim 1, which has an absorption band near 400 cm ^-1 . 3. The high-purity opaque quartz glass according to claim 1, wherein the viscosity at 1,260 ° C. is 10 ^12.8 poise or more, and 90% or more of the gas component in the bubbles is nitrogen gas. 4. Crystalline quartz powder having a specific surface area of 0.01 to 100 m ² / g in an ammonia atmosphere of 600 to 1,
After heating to a temperature range of 300 ° C. to carry out ammonification, the ammonified quartz powder is subjected to 1, 2
A method for producing opaque quartz glass, which comprises heating and melting at 600 to 2,000 ° C.