JP3270798B2 - Method for producing silicon carbide sintered body - Google Patents

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 sintered body suitable for a jig for manufacturing semiconductors.

[0002]

2. Description of the Related Art Due to its excellent heat resistance and high-temperature strength, silicon carbide sintered bodies are used, for example, in process tubes and liner tubes used for manufacturing sintering shelves, heat engine parts, and other semiconductor elements. Attention has been paid to jig materials for wafer boats and the like, and their practical use is being promoted.

Generally, such a silicon carbide sintered body is
High density is achieved by impregnating silicon into silicon carbide or a molded body made of silicon carbide and carbon, silicifying carbon, and filling voids with silicon. The production method of this silicon carbide sintered body by reaction sintering is described in, for example,
-270917 and the like.

[0004]

According to the method for producing a silicon carbide-based sintered body, a high-density silicon carbide-based sintered body can be obtained, but cracks occur in the fired product after silicidation. May have occurred.

When the cause of the cracks was examined, it was found that, unlike other metals, silicon has the property of expanding its volume when it is solidified. It was found that cracks occurred.

[0006]

As a result of repeated studies for suppressing the occurrence of cracks as described above, the present inventors have found that the cooling process after the silicidation gradually cools the silicon when passing through the melting point of silicon. By doing so, it has been found that the occurrence of cracks can be significantly suppressed, and the present invention has been achieved.

More specifically, the method for producing a silicon carbide sintered body of the present invention comprises impregnating silicon carbide or a compact comprising silicon carbide and carbon with silicon at a temperature equal to or higher than the melting point of silicon in a non-oxidizing atmosphere. The method for producing a silicon carbide sintered body containing metallic silicon comprises a step of gradually cooling at least a temperature range of ± 10 ° C. of the melting point of silicon at 12 ° C./hr in a temperature decreasing process after the silicon impregnation step. It is characterized by the following.

Hereinafter, the present invention will be described in detail. In order to manufacture the high-purity silicon carbide sintered body of the present invention, silicon carbide or a molded body made of silicon carbide and carbon is produced. For such a compact, 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 from submicron to several tens of μm, but is 10 μm in consideration of the mechanical properties of the sintered body.
It is desirable to do the following.

Next, the powder is formed into a desired shape by a known molding method, for example, press molding, extrusion molding, casting molding, cold isostatic pressing and the like. In some cases, the molded body may be calcined at 1300 to 2100 ° C. to increase the molded body strength.

[0010] Thereafter, a resin such as a phenol resin, an epoxy resin, a urethane resin, a melamine resin, or the like, which is left behind when thermally decomposed, is dissolved in a solvent and introduced into the pores of the molded or calcined body. . Since the resin is dissolved in the solvent, it is uniformly introduced into the pores. Then, the molded body or the calcined body into which the resin is introduced is thermally decomposed at 800 to 2000 ° C. to generate carbon. At this time, since carbon is uniformly present in the silicon carbide molded body, the mechanical strength of the silicon carbide sintered body after reaction sintering can be improved.

In addition to the above-described method of introducing carbon, a predetermined amount of carbon powder may be mixed with silicon carbide powder as a starting material, followed by molding.

Next, the compact or calcined body is brought into contact with molten metal silicon at a temperature higher than the melting point of silicon, specifically at a temperature of 1414 ° C. or higher, to introduce silicon into the pores of the sample. I do. If the temperature is lower than this, the metal silicon does not melt and the reaction between silicon and carbon takes time. Then, the introduced metallic silicon reacts with carbon in the calcined body to generate silicon carbide. This reaction causes volume expansion and promotes densification. In addition, even when a complete dense body made of silicon carbide cannot be obtained, an apparently complete dense body can be obtained because metal silicon fills the remaining pores.

According to the present invention, in the cooling step after the above-mentioned silicidation, the melting point of silicon, ie, 1414 ° C. ± 10 ° C.
It is important to gradually cool the temperature range of 12 ° C./hr or less, particularly 10 ° C./hr or less. This slow cooling temperature range only needs to include the above-mentioned temperature range, and in a temperature range other than this temperature range, cooling may be performed at a temperature lowering rate exceeding 12 ° C./hr. Incidentally, the cooling rate at the time of cooling is about 600 to 1200 ° C./hr.

In the present invention, the cooling rate is set in the above-mentioned range because if the temperature is higher than 12 ° C./hr, the volume expansion when silicon is solidified occurs rapidly, resulting in cracks in the silicide.

[0015]

In a cooling process after silicon is impregnated with silicon carbide or a compact made of silicon carbide and carbon and subjected to a silicification treatment, volume expansion occurs when the silicon is solidified. This expansion may cause cracks in the molded product.

According to the present invention, in the cooling process after the silicidation, the temperature range of ± 10 ° C. of the melting point of silicon is set to 12 ° C./h.
When gradually cooled at a temperature lowering rate of r, expansion when molten silicon solidifies near the melting point of silicon gradually progresses. As a result, cracks can be suppressed even in the final product because other parts absorb the gradual volume expansion.

Thus, even in mass production, a highly reliable silicon carbide sintered body can be manufactured with a high yield with few defective products.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Example 1 Carbon powder was mixed with silicon carbide powder having an average particle size of 1.5 μm at a ratio of 5% by weight, and the mixture was press-molded to form a 60 × 70 powder.
It was formed into a shape of × 7 mm. After calcining the molded body at 1600 ° C., a paste of silicon powder was applied to the surface of the molded body.

This was subjected to a silicidation treatment at 1500 ° C. for 1 hour under a reduced pressure of 1 torr, and was then cooled in the temperature range shown in Table 1 at the rate shown in Table 1. The temperature region outside this range was cooled by standing cooling (600 ° C./hr or more).

[0020]

[Table 1]

According to the results of Samples Nos. 1 to 6 in Table 1, in Sample No. 6 in which the cooling rate exceeds 12 ° C./hr, the crack generation rate was extremely high. 1
By controlling the temperature to 2 ° C./hr or less, the occurrence of cracks could be remarkably suppressed.
From the results of Samples Nos. 7 to 11, cracks were observed in Sample No. 11 in which the control temperature range was narrower than the melting point of silicon ± 10 ° C. However, by gradually cooling the temperature range including the melting point of silicon ± 10 ° C., it was possible to prevent the occurrence of cracks.

[0022]

As described in detail above, according to the present invention, it is possible to suppress the occurrence of cracks due to volume expansion during the solidification of silicon after silicification, to improve the yield during mass production, and to improve the reliability. A high silicon carbide sintered body can be manufactured.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/573 C04B 41/87

Claims (1)

(57) [Claims] 1. A method for producing a silicon carbide sintered body containing metallic silicon obtained by impregnating silicon carbide or a compact comprising silicon carbide and carbon in a non-oxidizing atmosphere at a temperature not lower than the melting point of silicon. The temperature range of at least ± 10 ° C. of the melting point of silicon in the temperature decreasing process after the silicon impregnation step
A method for producing a silicon carbide based sintered body, comprising a step of gradually cooling at a temperature lowering rate of not more than hr.