JPH04139033A - Production of sio2-c composite material and sio2-sic composite material - Google Patents

Abstract

PURPOSE:To produce a dense, high-purity SiO2-C composite material and SiO2-SiC composite material at low cost by precipitating a specified amt. of carbon in a synthetic quartz glass porous body by thermal decomposition of hydrocarbon gas and then subjecting the glass to heat treatment at specified temp. CONSTITUTION:SiCl4 or the like is thermally decomposed or oxidized in flame, etc., to produce SiO2 fine particles, which are deposited to obtain a synthetic quartz glass having about 0.3g/cm<3> bulk density, about 12m<2>/g specified surface area and about 0.2mum average particle diameter. In this porous body of synthetic quartz glass, carbon is produced and precipitated by <=1.0 molar ratio by thermal decomposition of hydrocarbon gas or halogenated hydrocarbon gas at about 1000 deg.C in order to produce a porous SiO2-C composite material. This SiO2-C composite material is heat-treated at 1200 to <1600 deg.C to obtain a dense SiO2-C composite material, or heat-treated at 1600-2000 deg.C to produce SiC and to obtain a SiO2-SiC composite material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing a dense SiO□-C composite material and a SiO□-SiC composite material that can be used as a high-purity heat-resistant material in semiconductor manufacturing processes, etc. Regarding.

In the past, many furnace tubes and jigs and tools used during heat treatment of silicon wafers in the manufacturing process of semiconductors such as LSIs were made of high-purity quartz glass.

In the case of quartz glass, it has the advantage that it can be manufactured with high purity relatively easily, and that it does not change in quality or deform at a heat treatment temperature of about 1000°C.

However, in the process of heat-treating silicon wafers at a temperature of about 1200°C, viscous deformation of quartz glass becomes a problem, making it unusable, and high-purity silicon carbide heat-resistant materials cannot be used in such high-temperature areas. is being attempted.

Silicon carbide is said to have been discovered by E. G. Acheson in 1981, and the Acheson method, in which it is synthesized from silica stone and coke by the following solid phase reaction (1), is the first industrial production method.

5in2+3CSiC+2CO (1) However, with the recent improvement in the degree of integration of LSIs, the negative effect on silicon wafers of trace impurities contained in core tubes and silicon wafer support members using silicon carbide heat-resistant materials has become a problem.

Therefore, as well as increasing the purity of silicon carbide heat-resistant materials, there is also an increasing demand for increasing the heat resistance of quartz glass.

S1 was invented as a method for producing high-purity silicon carbide materials
Even with the impregnation method (Japanese Patent Application Laid-Open No. 57-43553),
If the silicon carbide-based raw material powder is poorly stored or if there is contamination in the manufacturing process including the S1 impregnation step, there is a problem that the material becomes unsuitable as a heat-resistant material for semiconductor heat treatment.

In addition, synthetic quartz glass, which has no other purity, has insufficient heat resistance, so it is mainly used at temperatures up to 1100℃.
The problem was that it could only be used in a lower temperature range. Technologies to improve the heat resistance of quartz glass include:
As shown in Japanese Patent Application Laid-Open No. 1-126238,
There is a method in which crystal nuclei are generated on the surface layer of quartz glass and crystallized into a highly heat-resistant cristobalite phase at high temperatures.

Although this method is effective in improving heat resistance, there is a large difference in thermal expansion coefficient between the quartz glass base material and the cristobalite phase, so cracks are generated by cooling after the cristobalite phase has been precipitated. There were problems in that it caused dust generation and caused destruction of heat-resistant members.

The present invention was invented in view of the above-mentioned problems, and
Dense 5iOz that can be used as a relatively low-cost, high-purity, heat-resistant material in semiconductor manufacturing processes, etc.
The present invention aims to provide a method for manufacturing C composite and 5102 SIC composite.

In order to achieve the above-mentioned purpose, S10□- according to the present invention
The manufacturing method of the C composite material is to precipitate carbon produced by thermal decomposition of gas containing hydrocarbon gas or halogenated hydrocarbon gas in a porous body of synthetic quartz glass at a molar ratio of 1.0 or less to form porous SiO2. □-C composite material is produced, and then this porous SiO□-C composite material is heated to 160°C above 1200°C.
It is characterized by being densified by heat treatment at a temperature below 0°C.

Further, in the method for manufacturing the 5102-3IG composite material according to the present invention, carbon generated by thermal decomposition of a gas containing hydrocarbon gas or halogenated hydrocarbon gas is added to a porous body of synthetic quartz glass at a molar ratio of 1.0. In the following analysis, porous S
produce an iO□-C composite, and then this porous SiO□
It is characterized in that SiC is generated by heat-treating the -C composite material at a temperature of 1600° C. or higher and 2000° C. or lower.

Hereinafter, the manufacturing method according to the present invention will be explained in more detail.

The manufacturing method of ultra-high purity synthetic quartz glass using the vapor phase method is
M CV D (Modified Chemical
Vapor Deposition I method, OV D
(Outside Vapor Desposi-
tion) method, V A D (Vapor-phase
Techniques collectively referred to as soot methods, such as the axial deposition method, have been developed and put into practical use for purposes such as manufacturing optical fibers.

A porous body of vapor-phase synthetic quartz glass is produced by vaporizing silicon chloride such as silicon tetrachloride and performing the following hydrolysis reaction (2) or oxidation reaction (3) in an oxidizing atmosphere such as a fire. Manufactured by depositing silicon fine particles.

5xC14+2H20510□+41(C1(2)SI
C14+0□ -5iOz+2CI□ (3) The porous body of vapor-phase synthetic quartz glass produced in this way is separated from halogen gases such as HCI and c1□ at the stage of depositing fine particles, so halogen gases are synthesized. It is known that it is possible to prevent the contamination of impurity metal compounds produced by corrosion of the container, resulting in extremely high purity silicon dioxide, and that the content of impurity metal elements is 1 ppm or less.

The present inventors have considered that by heat-treating the synthetic quartz glass porous body in an atmosphere containing high-purity hydrocarbon gas or halogenated hydrocarbon gas, carbon is uniformly precipitated even inside the porous body. However, if the 5iOz-C porous body obtained in this way with a carbon molar ratio of 1.0 or less is fired at a temperature of 1200°C or higher and lower than 1600°C, it can be densified due to the viscosity of synthetic silica glass. Due to the high purity of the starting raw materials and the fact that there is no mixing or molding process involved, extremely pure and dense 5i
It was discovered that an O7-C composite material can be produced, and the present invention was completed.

In addition, if a similarly obtained 5iOz-C porous body with a carbon molar ratio of 1.0 or less is fired at a temperature of 16 (10°C or higher), silicon carbide will be generated from the precipitated carbon and synthetic silica glass. Both (2) densification is possible due to the viscosity of the surplus synthetic quartz glass, and the starting material is of high purity,
It has also been discovered that a dense SiO□-3iC composite material with extremely high purity can be produced due to the fact that mixing of raw materials and molding steps are not included, and the present invention has been completed.

By using a porous body of ultra-high purity synthetic quartz glass as 5102 (silicon dioxide) in formula (1) above, heat treatment is performed in an atmosphere containing hydrocarbon gas or halogenated hydrocarbon gas. Carbon is uniformly deposited even inside the body, resulting in a 5xCh-C porous body similar to that obtained by microscopically mixing silicon dioxide and carbon.

At this time, the molar ratio of precipitated carbon is 1.0 or less.
If the iOz-C porous body is fired at a temperature of 1200°C or higher, the densification of the SiO□-C porous body will proceed due to viscous sintering of the synthetic silica glass, and if it is lower than 1600°C, a reaction between carbon and silica glass will occur. Therefore, a dense 5zOz C composite material can be obtained.

At this time, if the molar ratio of carbon to silicon dioxide in the SiO□-C porous body exceeds 1.0, the carbon covering the quartz glass will prevent sintering due to the viscous flow of the quartz glass, so the dense SiO □-C composite material cannot be obtained.

In addition, 5i0 in which the molar ratio of precipitated carbon is 1.0 or less
When firing the 2-C porous material, from the thermodynamic calculation results shown in Figure 1, the standard free energy (△G°) in equation (1) above starts to become negative at a temperature of 1600°C or higher, and the synthesis It can be seen that part of the quartz glass becomes silicon carbide. At this time, in a 5iO2-C porous body in which the molar ratio of carbon exceeds 1.0, most of the synthetic quartz glass becomes silicon carbide, and since silicon carbide is a difficult-to-sinter substance, the dense 5i02
-5iC composite material cannot be obtained. Therefore, 160(1
At a firing temperature of C or higher, the molar ratio of carbon in the porous body of synthetic quartz glass in which carbon is precipitated must be 1.0 or less.Furthermore, even in this composition range,
At temperatures exceeding 000°C, the volatilization of silicon monoxide shown by the following formula (4) becomes remarkable, resulting in a dense SiO□-3iC
Composite materials cannot be obtained in good yield.

SiO2+ CSiO+ GO(4)! The following describes the SiO□-C composite material and SiO□ according to the present invention.
Examples and comparative examples of the method for manufacturing -5iC composite materials will be described.

High-density 0.3 g/cm" synthesized by VAD method,
A porous body of synthetic quartz glass with a specific surface area of about 22 rn2/g and an average particle size of about 0.2 μm was heated at 1000 °C in various atmospheres with different CH and gas concentrations (diluted with Ar gas).
Heat treatment was performed at .degree. C. for 30 minutes to deposit carbon even into the interior of the synthetic silica glass porous body, thereby obtaining a SiO□-C porous body in which silica glass fine particles were coated with carbon.

The molar ratios of silicon dioxide and carbon at this time were as shown in Table 1.

The S10□-C porous body obtained here was
When fired at a temperature of 0°C for 3 hours, as shown in Table 1, Si with a molar ratio of precipitated carbon of 10 or less was formed.
When the O□-C porous body was fired, densification of the 5iO7-C porous body progressed due to viscous sintering of the synthetic silica glass, and a dense SiO□-C composite material was obtained. At this time, SiO□-C
If the molar ratio of carbon to silicon dioxide in the porous body exceeds 1.0, the carbon covering the silica glass will prevent sintering due to the viscous flow of the silica glass, resulting in a dense SiO
□-C composite material was not obtained.

In addition, 5iOz in which the molar ratio of precipitated carbon is 10 or less
If the -C porous body was fired at a temperature of 20[10°C, as shown in Table 1, part of the synthetic quartz glass became silicon carbide, and a dense SiO□-5iC composite material was obtained. . At this time, in a 5in2-C porous body in which the molar ratio of carbon exceeds 1.0, most of the synthetic quartz glass becomes silicon carbide, and since silicon carbide is a difficult-to-sinter substance, it is difficult to sinter, so the dense 5xOa
No SiC composite material was obtained. Therefore, 2.
At a firing temperature of 000° C., the molar ratio of carbon in the porous body of synthetic quartz glass in which carbon has been precipitated must be 1.0 or less.

(Margins below) Table 1 Table 2 Also synthesized by VAD method, the bulk density is about 0.3 g/
cm”, specific surface area is approximately 12 m27 g, average particle size is approximately 0.2 cm
A synthetic quartz glass porous body with a diameter of 40% CH4 gas (
Heat treatment was performed at 1000°C for 30 minutes in an atmosphere (diluted with Ar gas), and carbon precipitated even inside the synthetic silica glass porous body. Obtained. The molar ratio of silicon dioxide to carbon at this time was 1:0.5.

The 5iD2-C porous material obtained here was heated to 1100°C under reduced pressure.
When the 5102-C composite material was fired for 3 hours in a temperature range of 1,600°C to 1,600°C, densification of the 5102-C composite material progressed in a temperature range of 1,200°C to 1,600°C, as shown in Table 2.

When fired at 1500°C, the SiOg-C composite becomes completely densified, and its strain point temperature (viscosity coefficient is 1014
The temperature at which it becomes 'poise' was approximately 1100°C, and it had higher heat resistance than conventional quartz glass.

The impurity metal element concentration of this SiO□-C composite material is 1pp.
□ or less, and it was a very high purity 5iOz-C composite material.

When the SiO□-C porous body obtained in the same manner as in the above-mentioned example was fired at a temperature range of 1500°C to 2100°C for 3 hours under reduced pressure, the
β-type silicon carbide was generated in a temperature range of 0° C. or higher and 2000° C. or lower, resulting in a dense SiO□-5iC composite material. When fired at 1800℃, SiO□-5
Strain point temperature of iC composite material (viscosity coefficient is 10'4'pois
The temperature at which quartz glass becomes e is about 1200°C, and it has higher heat resistance than conventional quartz glass.

The impurity metal element concentration of this SiO□-3iC composite is 1
．． 1 or less, resulting in an extremely pure 5LOa-SiC composite material.

As is clear from the above explanation, SiO□ according to the present invention
According to the manufacturing method of the -C composite material and the Sing-5iC composite material, the molar ratio of carbon produced by thermal decomposition of a gas containing hydrocarbon gas or halogenated hydrocarbon gas in a porous body of synthetic quartz glass is 1. .0 or less to produce a porous 5i02-C composite, and after sono porous 5
The iCh-C composite material is densified by heat-treating it at a temperature of 1200 °C or more and less than 1600 °C, and contains hydrocarbon gas or halogenated hydrocarbon gas in the porous body of synthetic quartz glass. Carbon produced by thermal decomposition of gas is precipitated at a molar ratio of 1.0 or less to produce a porous 5102-C composite, and then this porous 5i0
It is characterized by generating SiC by heat-treating the 2-C composite material at a temperature of 1,600°C or higher and 2,000°C or lower. SiO□ can be mixed and then densified using the viscous flow of glass, resulting in extremely high purity and even higher heat resistance than quartz glass.
-C composite and 5102 SiC composite can be obtained.

Therefore, dense Si can be used as a relatively low-cost, high-purity, heat-resistant material in semiconductor manufacturing processes.
O□-C composites and SiO□-SiC composites can be provided.

[Brief explanation of drawings]

FIG. 1 is a graph showing the standard free energy calculation results for the reaction of formula (1).

Claims (2)

[Claims] (1) A porous SiO_2-C composite is created by precipitating carbon produced by thermal decomposition of gas containing hydrocarbon gas or halogenated hydrocarbon gas at a molar ratio of 1.0 or less into a porous body of synthetic quartz glass. and then this porous S
A method for producing a SiO_2-C composite material, characterized in that the iO_2-C composite material is densified by heat-treating the iO_2-C composite material at a temperature of 1200°C or more and less than 1600°C. (2) A porous SiO2-C composite is created by precipitating carbon produced by thermal decomposition of gas containing hydrocarbon gas or halogenated hydrocarbon gas at a molar ratio of 1.0 or less into a porous body of synthetic quartz glass. and then this porous Si
A method for producing a SiO_2-SiC composite material, comprising generating SiC by heat-treating the O_2-C composite material at a temperature of 1600°C or higher and 2000°C or lower.