JPS5848487B2 - Method for producing high purity silicon carbide powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity silicon carbide powder suitable as a raw material for semiconductor manufacturing jigs or soaking tubes.

Conventionally, in order to produce silicon carbide in large quantities, silica powder and carbon powder were added with sawdust salt, etc., filled into an electric furnace, and then the silica powder and carbon powder were reacted by resistance heat generation in the core in the furnace. ing.

However, in this method, the temperature is highest around the core and gradually decreases toward the outer furnace wall, resulting in an unreacted layer remaining on the outer periphery and a temperature range in which impurities in the raw materials tend to condense. There is a risk that the amount of impurities in the formed silicon carbide may be unevenly distributed, or that the silicon carbide may form a polycrystalline aggregate called an incott.

Therefore, by pulverizing it or stirring and mixing it, C.
Since it is necessary to ensure uniform distribution of impurities such as .

The present invention was made in view of the above circumstances, and aims to obtain highly pure silicon carbide powder that is in powder form and can be used as a variety of raw materials without any grinding or stirring processes that cause secondary contamination. It is.

The present invention will be explained in detail below.

First, high-purity silica powder with a particle size of 5 CIfL or less and high-purity carbon powder with a particle size of 5 wIl or less are filled into, for example, a cylindrical graphite container and sealed.

Next, this container is continuously moved to a graphite tube furnace, and while flowing a non-oxidizing gas such as nitrogen gas into the furnace, the temperature inside the furnace is adjusted to a temperature range that can convert silicon carbide without causing significant grain growth. The temperature is maintained at 1800 to 2200°C to react silica stone and carbon to produce silicon carbide powder.

As the high-purity silica powder used in the present invention, for example, silica stone for quartz glass is crushed and sieved, then boiled in hydrochloric acid and dehydrated.
These include those that have been dried and purified.

In addition, as the high-purity carbon powder used in the present invention, for example, after crushing and sieving petroleum coke,
It is purified by spraying salt gas at a temperature of ℃.

Furthermore, the reason why the particle diameters of the high-purity silica stone powder and high-purity carbon powder in the present invention are limited to 571 gI1 or less is that if these particle diameters exceed 51 ml, powdered silicon carbide cannot be obtained in good yield. be.

The mixing ratio of the silica powder and carbon powder is usually such that the molar ratio of silica powder to carbon powder is 1:3.

Further, the moving speed of the graphite container filled with silica powder and carbon powder in the furnace may be appropriately selected depending on the amount of filling, the temperature inside the furnace, etc.

According to the present invention, high-purity silica powder and high-purity carbon powder are sealed in a graphite container and moved into a tubular furnace, thereby uniformly heating the silica powder and carbon powder. High-purity silicon carbide powder that can be used as a raw material for various raw materials without any grinding or stirring processes that can cause secondary contamination due to processing at a temperature that allows reaction and does not cause significant grain growth. can be obtained as

Beak Bone Next, embodiments of the present invention will be described.

Example 1 After crushing and sieving silica stone for quartz glass, it was immersed in a hydrochloric acid solution for 1 hour, boiled, washed with water, dehydrated, and dried to produce silica powder having a particle size distribution and impurity content shown in Table 1 below.

On the other hand, after crushing and sieving the petroleum coke, it was
While heating to 0'C, chlorine gas was sprayed for 2 hours.
Carbon powder with the hardness distribution and impurity content shown in the table was produced.

Next, the silica powder and carbon powder were mixed at a molar ratio of 1:3, and this mixed powder was filled into a cylindrical graphite container (outer diameter 160 m, inner diameter 1357EJ length 1000 m) and sealed.
This container has an inner diameter of 17071lIIl and a length of the heating part of 20
The container was placed in a graphite tubular furnace of 0.0071gIl, and the container was moved by a plunger at a speed of 500.11m/Hr, and the temperature inside the furnace was raised to 1900°C while supplying nitrogen gas into the furnace.
The silica stone and carbon in the container were reacted at ±20°C to obtain silicon carbide powder.

The yield of the obtained silicon carbide powder was 91%, and when its particle size distribution and impurity content were examined, the results shown in Table 2 below were obtained.

As is clear from the above table, the silicon carbide obtained by the method of the present invention is in powder form and has high purity, and can be used as it is as various raw materials.

Example 2 Same as Example 1 above, except that the moving speed of the circle*water cylindrical graphite container filled with the silica powder and carbon powder shown in Table 1 above was set at 400 m/Hr, and the temperature inside the furnace was set at 2100°C. Silicon carbide powder was obtained using this method.

The hardness distribution and impurity content of the obtained silicon carbide powder were investigated.

The results are shown in Table 3 below. As described in detail above, according to the present invention, it is possible to easily obtain high-purity silicon carbide in powder form and with a uniform distribution of impurities, and there is no need for a grinding process or stirring/mixing process that causes secondary contamination. It has remarkable effects such as being able to be suitably used as a raw material for components such as jigs for semiconductor manufacturing and soaking tubes for semiconductor manufacturing, which require extremely low volatilization of impurities.

Claims (1)

[Claims] 1. Mix high-purity silica powder with a particle size of 5 m or less and high-purity carbon powder with the same particle size, and fill it into a sealed graphite container.The container is then continuously moved to a tube furnace. Temperature 1
A method for producing high-purity silicon carbide powder, which comprises maintaining the temperature at 800 to 2200°C to react the silica stone and carbon in the container.