JPH08151268A - Production of silicon carbide sintered compact - Google Patents

Abstract

PURPOSE: To obtain a silicon carbide sintered compact reduced in free silicon left on the surface of the sintered compact after a silicification treatment, excellent in processability, capable of reducing heat generation and rapid volume expansion due to the reaction of carbon with silicon, and free from cracks. CONSTITUTION: The method for producing the silicon carbide sintered compact by impregnating a molded product comprising silicon carbide and carbon with metallic silicon at >= the melting point of the silicon to silicify the carbon is provided with a gradually temperature-raising process performed at a temperature-raising rate of <=5 deg.C/min in a temperature region ranging from the 1200 deg.C to a silicification temperature in the temperature-raising process in the silicification treatment in an atmosphere containing carbon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silicon carbide based sintered body suitable for a structural component or a semiconductor manufacturing jig.

[0002]

2. Description of the Related Art Sintered silicon carbide has attracted attention as a material for jigs such as process tubes, liner tubes, and wafer boats used for manufacturing structural parts such as gas turbine parts and semiconductor elements. Its practical application is in progress.

Generally, as a method for producing a silicon carbide-based sintered body, boron, which is known as a sintering aid for silicon carbide,
Carbon, oxide of Group 3a of the Periodic Table or Al ₂ O ₃
Auxiliary agent addition system that has been densified by adding etc.
Alternatively, a reaction sintering method is known in which a molded body made of silicon carbide and carbon is melt-impregnated with silicon and carbon is reacted with silicon to newly generate silicon carbide.

Further, the sintering method with addition of an auxiliary agent is 1900-23.
In contrast to sintering at a high temperature of 00 ° C, the reactive sintering method is
It can be sintered at a low temperature of 1450 to 1700 ° C. In addition, the auxiliary additive sintering method has a dimensional shrinkage of 15 to 20% during sintering, whereas the reactive sintering method has a dimensional shrinkage of 1 to 2% or less during sintering. Therefore, the reaction sintering method has been attracting attention as a method for obtaining a large-sized sintered body having a complicated shape. In addition, according to the reaction sintering method, it is often used as a sintered body for semiconductor manufacturing which requires high purity.

[0005]

However, according to the above-mentioned two manufacturing methods, since a post-sintering process is required to obtain a product, a large processing cost is required. In particular, since the sintered body obtained by the reaction sintering method has free silicon remaining after sintering, it takes time to process it for removing the free silicon.

Further, when this silicon carbide sintered body is used as a jig for semiconductor manufacturing, there is a problem that it cannot be used as a product if impurities are mixed in during processing because it requires high purity. There was also a problem that the method was limited to a special method.

Further, the reaction sintering method has a problem that cracks are generated in the sintered body due to heat generation and volume expansion due to the reaction between carbon and silicon. Particularly, when the sintered body has a large size, the generation of cracks becomes remarkable. .

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, in a step of melting and impregnating a molded body of silicon carbide and carbon with silicon to silicify carbon, By providing a gradual temperature raising step performed in a temperature range from 1200 ° C. or higher to the silicidation temperature at a temperature rising rate of 5 ° C./min or less and in an atmosphere containing carbon,
It has been found that a crack-free sintered body can be obtained because free silicon does not remain and heat generation and abrupt volume expansion due to the reaction of carbon and silicon can be suppressed.

The present invention will be described in detail below. In order to manufacture the silicon carbide-based sintered body of the present invention, first, silicon carbide powder is prepared as a raw material powder. As the silicon carbide powder, either α type or β type or a mixture thereof can be used. The average particle size of the silicon carbide powder may be any one of submicron to several hundreds of μm, but it is preferably 5 μm or less in consideration of the mechanical properties of the sintered body.

Then, the above-mentioned powder is molded into a desired shape by a known molding method such as press molding, extrusion molding, cast molding, cold isostatic molding and the like. Further, the obtained molded body can be heat-treated in a non-oxidizing atmosphere at 800 to 2000 ° C. to give shape retention.

After that, carbon is introduced into the above-mentioned compact or calcined body. As a method of introducing carbon, first, a resin that leaves carbon when thermally decomposed, for example,
Phenol resin, epoxy resin, urethane resin, melamine resin, etc. are dissolved in a solvent, and the molded body or calcined body is dipped or applied in this solution. Since the resin component is dissolved in the solvent, it is uniformly introduced into the pores of the molded body or the calcined body. Then, the molded body or calcined body after this treatment is
Carbon can be uniformly introduced by heat treatment in a non-oxidizing atmosphere at 00 to 2000 ° C. to thermally decompose and carbonize.

As a method of introducing carbon, in addition to the above, in the starting composition, the silicon carbide powder and the carbon powder, or the above-mentioned resin that causes residual carbon by thermal decomposition is premixed, and this mixed powder is prepared in the same manner as above. It may be molded into a desired shape by a known molding method.

When introducing these carbons, the amount of carbon to be introduced is 2 to 5 for the total amount of silicon carbide and carbon.
It is desirable to control the content to be 0% by weight. This is because unreacted carbon remains if the amount of carbon is larger than this amount, and if the amount of carbon is less than this amount, Si is completely contained inside the sample.
This is because it becomes difficult to impregnate

Next, the introduced carbon is silicified by bringing the molded body or the calcined body into which the carbon has been introduced into contact with the molten silicon. As the method of this silicidation treatment, a silicon paste prepared by mixing silicon powder with an organic solvent and an organic binder is applied to the surface of a molded body or a calcined body, and this is above the melting point of silicon, that is, 1414 ° C. Heat to the above temperature. By this heating, the molten silicon penetrates into the molded body or the calcined body, is brought into contact with the carbon component, and silicon carbide is newly generated by silicidation of carbon.

Since the volume expansion occurs due to the generation of silicon carbide by the silicidation of carbon, the compacted body and the calcined body are densified. Further, even when the pores are not entirely filled with the newly generated silicon carbide, a completely dense body can be obtained because the remaining pores are filled with metallic silicon.

According to the present invention, in this silicidation treatment, the rate of temperature rise is 5 ° C./min or less, particularly 3 ° C./min in the temperature range from 1200 ° C. to the silicidation temperature during the temperature rising process from room temperature to the silicidation temperature. It is important to provide a so-called gradual temperature raising step of treating in a carbon-containing atmosphere at a temperature of min or less. As a carbon-containing atmosphere, silicidation is performed in a carbon pot, a compact or a calcined body is embedded in carbon powder for treatment, or a gas such as carbon monoxide is introduced into the atmosphere in the furnace. May be. The rate of temperature increase in this gradual temperature increase step includes the case of maintaining the temperature increase rate of 0 ° C./min, that is, a certain temperature from 1200 ° C. to the silicidation temperature for a predetermined time. The treatment time in this gradual temperature raising step varies between about 30 minutes and 3000 minutes depending on the temperature and the temperature raising rate.

After reaching the silicidation temperature, the atmosphere is set to a vacuum or a non-oxidizing atmosphere such as argon, treatment is carried out until the silicidation of carbon completely progresses, and then cooled to room temperature.

The holding time at the silicidation temperature is about 0.
5-10 hours is suitable.

[0019]

According to the present invention, there is provided a gradual temperature raising step of performing treatment in a carbon-containing atmosphere having a temperature raising rate of 5 ° C./min or less within a temperature range from 1200 ° C. to a silicifying temperature at the time of temperature raising in the silicidation treatment of carbon. To do. This gradual temperature raising step is to generate silicon carbide by reacting silicon existing on the surface of the compact or the calcined body with carbon or carbon monoxide in the atmosphere in the silicidation treatment. Since this silicon carbide film can be easily removed, it is possible to prevent free silicon from adhering to the surface after the silicidation treatment. As a result, it is not necessary to remove free silicon after the silicidation treatment, and the processing can be easily performed. If the rate of temperature increase at 1200 ° C. or higher is higher than 5 ° C./min, the reaction between the coated silicon and carbon or carbon monoxide does not proceed, and a silicon carbide film cannot be obtained. Free silicon adheres to the surface of the bonded body, which makes it difficult to remove and process the free silicon.

Also, at a temperature of 1200 ° C. or higher, 5 ° C./mi
Since the heat generation amount and the rapid volume expansion due to the reaction of carbon and silicon can be suppressed by setting the ratio to be n or less, a sintered body without cracks can be obtained. This is because the reaction between carbon and silicon starts at around 1200 ° C. and the reaction rate can be gently controlled by raising the temperature at 5 ° C./min.

[0021]

【Example】

Comparative Examples 1 and 2, Examples 1 to 10 were added to silicon carbide powder having an average particle diameter of 1.5 μm so that the residual carbon content when the phenol resin was thermally decomposed was 2% by weight,
After kneading and drying this, it was passed through a sieve to obtain molding granules. These granules are molded by a die press, 50 × 60 × 7mm
A molded body of was produced. The porosity of the obtained molded body is 40%
Met. Then, the molded body was impregnated with a solution in which a phenol resin was dissolved to introduce the phenol resin. The total amount of introduced carbon was 4%.

Thereafter, a silicon paste was applied to the surface of the molded body, the sample was placed in a carbon furnace and heated at a temperature of 1450 ° C. for 0.5 hour to perform a silicidation treatment. At this time, Table 1
The temperature range shown in was carried out at a temperature rising rate of 0.1 to 10 ° C./min. In addition, until reaching the temperature range of Table 1, 10 ℃
The temperature was raised at a heating rate of / min. Then, after observing the surface properties of the silicidated sample, it was polished and cracks were observed.

Example 11 In the silicidation treatment in Examples 1 to 10, the temperature rising rate from 1200 ° C. to the silicidation temperature (1450 ° C.) was 0.5 ° C./min, and the compact was embedded in carbon powder to silicify. Processed. After observing the surface properties of the silicidated sample,
Polished and observed cracks.

Comparative Example 3 In the silicidation treatment in Examples 1 to 10, the temperature was changed from 1200 ° C. to the silicidation temperature at 0.5 ° C./min, the treatment was performed in a vacuum using a tungsten furnace, and the surface properties of the samples were similarly observed. After that, polishing was performed and cracks were observed.

Comparative Example 4, Examples 12 to 15 In the silicidation treatment in Examples 1 to 10, the sample was placed in a carbon furnace and temporarily held at the temperature shown in Table 1 (heating rate 0 ° C./min). Was processed as. The temperature raising process before and after maintaining the primary temperature was set at a temperature raising rate of 10 ° C./min. Then, similarly, after observing the surface properties of the sample, polishing was performed and cracks were observed.

[0026]

[Table 1]

According to Table 1, the temperature rising rate of 1200 ° C. or more and the temperature rising rate of 0 to 5 ° C./min or less and the silicidation treatment in the carbon-containing atmosphere have no free silicon, and even if it is present, it is very small. In addition, the silicon carbide film was formed on the surface, and the silicon carbide film could be easily peeled off. Moreover, no cracks were found in the sintered body.

On the other hand, in Comparative Examples 1 and 2 in which the temperature rising rate exceeds 5 ° C./min and Comparative Example 4 in which the holding temperature is lower than 1200 ° C., a large amount of free silicon is attached to the surface,
Silicon could only be removed by grinding. Moreover, cracks were generated in the sintered body. Further, in Comparative Example 3 performed in the tungsten furnace containing no carbon even if the temperature rising rate was 5 ° C./min or less, cracks were not generated, but a large amount of free silicon was attached to the silicon carbide film. Was not observed.

From these results, it was found that according to the method of the present invention, since the adhesion of free silicon to the surface can be suppressed, the workability is remarkably improved, and the occurrence of cracks due to silicidation can be prevented.

[0030]

As described in detail above, according to the present invention, it is possible to suppress the residual of free silicon on the surface of the sintered body after the silicidation treatment, and obtain a silicon carbide based sintered body excellent in workability. it can. At the same time, heat generation and rapid volume expansion due to the reaction between carbon and silicon can be suppressed, and a sintered body without cracks can be obtained.

Claims (1)

[Claims] 1. A molded body made of silicon carbide and carbon,
A method for manufacturing a silicon carbide-based sintered body in which metallic silicon is impregnated at a temperature equal to or higher than the melting point of silicon to silicify the carbon, the method comprising: A method for producing a silicon carbide based sintered body, comprising a step of performing the heating step in a temperature range at a temperature rising rate of 5 ° C./min or less and in an atmosphere containing carbon.