JPH05124863A - Production of high purity silicon carbide body - Google Patents

Abstract

PURPOSE:To increase production efficiency by forming an SiC film on the surface of an Al2O3 substrate by chemical vapor deposition and then removing the substrate. CONSTITUTION:An Si-contg. compd. such as SiCl4 a C-contg. compd. such as CH4 and H2 are fed at prescribed flow rates to the surface of an Al2O3 substrate formed into a pipe shape, etc., and an SiC film is formed on the surface of the substrate by chemical vapor deposition at a high temp. of <=1,000 deg.c under reduced pressure in 100-2,000Xm thickness. After cooling to ordinary temp., the substrate is easily separated and a high purity SiC body is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of high-purity silicon carbide bodies used for crucibles for melting metals, thermocouple protection tubes, heating elements, semiconductor diffusion furnace members, optical fiber sintering furnace core tubes, etc. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, crucibles for melting metals, thermocouple protection tubes, heating elements, semiconductor diffusion furnace members, optical fiber sintering furnace core tubes, etc. have been made of graphite, sintered silicon carbide or reaction sintered silicon carbide. A high purity silicon carbide layer is formed on the surface of a substrate by coating the substrate with high purity silicon carbide.

Also known is a method of obtaining a high-purity silicon carbide body by forming a high-purity silicon carbide film on a graphite base material and then baking the graphite base material in an oxidizing atmosphere.

[0004]

However, a high-purity silicon carbide body obtained by coating high-purity silicon carbide on a graphite, sintered silicon carbide or reaction-sintered silicon carbide substrate is subjected to thermal cycling by repeated use. When receiving, there are problems that the substrate and the coating surface are separated, and that the substrate surface is exposed due to the generation of cracks. Therefore, in the case of a graphite substrate, the oxidation resistance is significantly reduced, and the sintered silicon carbide,
In the case of the reaction sintered silicon carbide substrate, there is a problem that impurities in the substrate diffuse to the outer surface.

Further, the method of obtaining a high-purity silicon carbide body by quenching a graphite base material requires a long time for the graphite base material to be burned out, and since the base material is burned out, the base material is repeatedly used. There are problems such as not being able to do it.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method for producing a high-purity silicon carbide body consisting only of chemical vapor deposited silicon carbide in a short time, efficiently and economically. To aim.

[0007]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by using an alumina base material as the base material. That is, the method for producing high-purity silicon carbide according to the present invention is carried out by chemical vapor deposition on the surface of an alumina base material, which is previously formed into a crucible shape, a heater shape, a furnace core tube shape, or the like, particularly preferably the outer surface. After forming the film, the alumina base material is removed to produce a high-purity silicon carbide body.

As described above, by chemically vapor-depositing the silicon carbide film on the surface of the alumina substrate, the alumina substrate and the silicon carbide film are easily separated by lowering the temperature after the chemical vapor deposition. That is, the linear expansion coefficient of alumina is about 0.79% at 1000 ° C., while the linear expansion coefficient of silicon carbide is 10%.
Since it is about 0.35% at 00 ° C., shear stress is applied to the joint surface between the alumina base material and the silicon carbide film due to the temperature drop, and this working stress facilitates the formation of the base material alumina and the silicon carbide film. To separate.

Therefore, according to the present invention, it is possible to easily remove the alumina base material by lowering the temperature after forming the silicon carbide film by chemical vapor deposition without the need for an operation such as punching out graphite. In addition, the process time can be shortened, a high-purity silicon carbide body can be efficiently manufactured in a short time, and the base alumina can be repeatedly used, so that the manufacturing cost can be reduced.

Further, since the silicon carbide body produced by the above method is only one formed by the chemical vapor deposition method, it is dense and at the same time extremely high in purity. Therefore, for example, when it is used in a furnace core tube for an optical fiber, there is no concern that impurities will be mixed into the fiber.

The present invention will be described in more detail below. In the method for producing a high-purity silicon carbide body of the present invention, a silicon carbide film is formed on a surface of a base material formed into a desired shape by alumina by a chemical vapor deposition method. After that, the alumina base material is removed by lowering the temperature.

Here, the chemical vapor deposition of silicon carbide can be carried out by a conventional method, and is usually a silicon-containing compound such as SiCl ₄ , Si at a high temperature of 1000 ° C. or higher and under reduced pressure.
HCl ₃ , SiH ₂ Cl ₂ , SiH _4, etc. and carbon-containing compound C
Method of reacting H ₄ , C ₃ H ₈ or the like, or compound CH ₃ SiCl ₃ , (CH ₃ ) ₂ Si containing silicon and carbon at the same time
It is made by thermal decomposition of Cl ₂ , (CH ₃ ) ₃ SiCl, (CH ₃ ) ₄ Si and the like.

In this case, the thickness of the silicon carbide film is appropriately selected, but is generally about 100 to 2000 μm.

Next, after the silicon carbide film is formed by chemical vapor deposition in this way, the temperature is lowered by a usual method to reduce the stress caused by the difference in the thermal expansion coefficient between the silicon carbide film and the alumina base material. By the action, the silicon carbide film and the alumina base material are easily desorbed without adding any other operation.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[Example] A pipe (outer shape 1) made of alumina
50 mm, length 300 mm) was molded, and at the reaction temperature of 1300 ° C., SiCl ₄ was 0.5 liter / min (SLM) and C ₃ H ₈ was 0.5 liter / min (SLM) on the outer surface of the alumina pipe. , H ₂ was supplied at a rate of 4 liters / minute (SLM), and the reaction system was evacuated by a pump to keep the reaction pressure at 10 Torr and deposit a silicon carbide film at 1500 μm.

Next, by returning the temperature to room temperature, the silicon carbide film was easily separated from the alumina pipe, whereby a high purity silicon carbide body without chemical vapor deposition SiC was manufactured.

Further, after the above method, the alumina pipe desorbed from the silicon carbide film was used again, and 30 high-purity silicon carbide bodies were repeatedly manufactured in the same manner as above, but the alumina pipe was damaged. There wasn't.

[0019]

According to the present invention, a silicon carbide body made of only high-purity silicon carbide can be produced efficiently and economically in a short time by a chemical vapor deposition method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyoshi Tamura 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (1)

[Claims] 1. A method for producing a high-purity silicon carbide body, which comprises forming a silicon carbide film on the surface of an alumina base material by a chemical vapor deposition method and then removing the alumina base material.