JPH11147766A - Silicon carbide sintered product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a problem that it is necessary to form a silicon carbide film on the surface of a sintered product, when an extremely smooth surface is required. SOLUTION: This silicon carbide sintered product which comprises a polycrystal and whose polished surface has a surface roughness of <= 3 nm as an average roughness on a central line by a contact type measuring method. The method for producing a silicon carbide sintered product comprises adding 0.1-0.8 wt.% of boron or its compound and 1-5 wt.% of carbon as sintering auxiliaries to silicon carbide powder having an average particle of <=0. 7 μm, molding the mixture, sintering the molded product in an inert gas atmosphere of 1900-2050 deg.C at the atmospheric pressure, subjecting the sintered product to a hot hydrostatic pressure press (HIP) treatment at a lower temperature than the sintering temperature under a pressure of >=1000 kg/cm<2> , and subsequently polishing the surface of the obtained HIP treatment product with diamond abrasive particles having an average particle diameter of <=2 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silicon carbide sintered body and a method for producing the same, and more particularly, to a silicon carbide sintered body having an extremely smooth polished surface and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, metal members such as stainless steel have been used to transport and hold a silicon wafer in a semiconductor manufacturing process.
With the increase in the density of circuit patterns, suppression of deformation of members,
Suppression of metal contamination, maintenance of accuracy over a long period of time, and the like have been demanded, and ceramic members have been increasingly used to cope with this. In addition, mirrors used in precision optical instruments such as laser devices are often made of ceramic members in order to avoid a decrease in accuracy due to thermal expansion. In many cases, alumina or silicon carbide is used for the ceramic member.

[0003] Of these ceramic members, those such as ceramic mirrors used for precision optical equipment or vacuum tweezers and hands used for handling Si wafers in the semiconductor industry leave dust and dirt on the surfaces thereof. Usually, required portions are ground and polished to make the surface smooth so as not to cause any adverse effects.

[0004] However, the pores of the ceramic material itself remain on the polished surface on the surfaces of these members, and the surface smoothness and the optical characteristics are not sufficiently satisfactory. This is mainly due to the fact that pores remain at grain boundaries between crystal grains in the sintered body in the course of sintering, for example, in the case of polycrystalline ceramics. For this reason, as a ceramic member requiring an extremely smooth surface, a member obtained by forming a silicon carbide film on the surface by a CVD (chemical vapor deposition) method and polishing the film is used.

[0005]

However, this method can produce a ceramic member having excellent surface smoothness, but requires an expensive apparatus in order to form a silicon carbide film on the surface of the member. This has contributed to the high cost of the ceramic member. In addition, when the silicon carbide film on the surface is polished,
Coupled with the brittleness of the silicon carbide film, the film was cracked, and the growth of the cracks could even break the film.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of ceramics requiring an extremely smooth surface, and has as its object to achieve extremely smooth polishing without forming a silicon carbide film on the surface. It is another object of the present invention to provide a silicon carbide sintered body having a surface and a method for manufacturing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, boron or a compound thereof and carbon as a sintering aid have been added to fine silicon carbide powder and molded. The present invention was completed by obtaining the knowledge that a sintered body having an extremely smooth surface can be obtained by sintering the formed body at a lower temperature than before and further subjecting the formed body to HIP treatment by polishing this surface. .

That is, the present invention provides: (1) In a silicon carbide sintered body made of polycrystal, the surface roughness of the polished surface of the sintered body is not more than 3 nm as a center line average roughness (Ra) by a contact method. (2) A silicon carbide powder having an average particle diameter of 0.7 μm or less, containing boron or a compound thereof as a sintering aid. 1 to
0.8% by weight and 1 to 5% by weight of carbon are added, molded, sintered at normal pressure in an inert gas atmosphere of 1900 to 2050 ° C., and then further sintered under a pressure of 1000 kg / cm ² or more. Hot isostatic pressing at a temperature lower than the sintering temperature (H
IP) treatment, and polishing the surface of the obtained HIP-treated body with diamond abrasive grains having an average particle size of 2 μm or less (claim 2). Make a summary. This will be described in more detail below.

As described above, the surface roughness of the polished surface of the silicon carbide sintered body having a smooth surface is set to 3 nm or less as a center line average roughness (Ra) by a contact method. 1). The surface roughness of the polished surface is equal to the surface roughness of the polished surface of the conventional silicon carbide film, and there is no need to form a silicon carbide film on the surface of the silicon carbide sintered body. If this exceeds 3 nm in Ra, for example, when used as a ceramics mirror, required characteristics such as insufficient optical characteristics cannot be obtained.

[0010] As a method of manufacturing the sintered body, 0.7 μm
m or less, and 0.1 to 0.8% by weight of boron or its compound as a sintering aid,
Carbon is added in an amount of 1 to 5% by weight, molded, and
After normal pressure sintering in an inert gas atmosphere at 2050 ° C., it is further subjected to hot isostatic pressing (HIP) at a temperature lower than the sintering temperature under a pressure of 1000 kg / cm ² or more,
A method of polishing the surface of the obtained HIP-treated body with diamond abrasive grains having an average particle size of 2 μm or less (claim 2).

The fineness of the silicon carbide powder used is set to 0.7 μm or less (more preferably 0.5 μm or less) in average particle size because the fineness enables sintering at a temperature lower than a normal sintering temperature. By sintering at the low temperature, a sufficient sintering density can be attained and grain growth can be suppressed to avoid coarsening of the pores. Is that it can be almost completely absent. If the fineness of the silicon carbide powder is coarser than 0.7 μm in average particle size, the low-temperature sintering property is lost and low-temperature sintering cannot be performed. If this is heated at a higher temperature, grain growth occurs and the pores become coarser.

Although the reason why the pores in the sintered body can be almost completely eliminated has not been theoretically elucidated, in the sintering of a silicon carbide powder having a normal roughness, the grain boundaries are increased with the progress of sintering. While the pores accumulate and grow in the phase and the pores become apparent,
With sufficiently fine silicon carbide powder, coupled with low-temperature sintering, pores having small diameters (called ghost pores) that cannot be observed with a microscope in crystal grains may occur, and pores may grow at crystal grain boundaries. Probably not.

As a sintering aid to be added to the silicon carbide powder, boron or its compound and carbon are preferable. When an oxide is used as a sintering aid, decomposition of the sintering aid occurs,
Gas is generated, causing pores. The added amount is preferably 0.1 to 0.8% by weight and 1 to 5% by weight, respectively. When boron or its compound is less than 0.1% by weight and carbon is less than 1% by weight, sintering is performed. Difficult, boron or its compound is more than 0.8% by weight and carbon is 5%.
When the content is more than the weight percentage, grain growth tends to occur during sintering, and pores become coarse.

As a method of sintering a molded body obtained by molding them, 1900 to 1900 in an inert gas atmosphere such as argon.
It was decided to perform normal pressure sintering at 2050 ° C. The sintering temperature is lower than the normal sintering temperature (2100 to 2200 ° C.), and sintering at this low temperature can suppress pore coarsening as described above. The temperature is 19
If the temperature is lower than 00 ° C., it is difficult to sinter densely. On the other hand, if the temperature is higher than 2050 ° C., the grain growth is remarkable, and the pores move to the grain boundary phase and the pores become coarse with the grain growth. The obtained sintered body is further subjected to 1000 kg in an inert gas atmosphere such as argon.
HIP treatment under a pressure of not less than / cm ² . This HIP
The processing can further reduce the pores and make them almost nonexistent. If the HIP pressure is lower than 1000 kg / cm ² , the effect of reducing pores is small, which is not preferable. The HIP treatment temperature needs to be lower than the sintering temperature from the viewpoint of suppressing pore coarsening due to grain growth.

The surface of the silicon carbide sintered body thus obtained is polished with diamond abrasive grains having an average particle size of 2 μm or less. Since the silicon carbide sintered body is a high-hardness material, polishing with abrasive grains other than diamond is not preferable because the required time is considerably long. If the fineness of the diamond is coarser than 2 μm in average particle size, the surface roughness becomes rough. Become
Smoothness required for ceramic mirrors and hands cannot be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention will be described in more detail. First, a silicon carbide powder having an average particle diameter of 0.7 μm or less is prepared, and boron or its compound is added as a sintering aid to 0.1%. 0.8% by weight and 1-5% by weight of carbon are added and molded. The shaping may be performed by a conventional method. For example, if the thin plate is made of vacuum tweezers or the like, the thin plate is formed by a doctor blade method or an extrusion molding method. It may be formed by isostatic pressing), molding or casting. In any case, an organic binder suitable for each molding method is used as a molding aid.

The obtained compact is sintered under normal pressure at a temperature of 1900 to 2050 ° C. in an inert gas atmosphere such as argon,
The obtained sintered body is further subjected to HIP treatment at a temperature lower than the sintering temperature under a pressure of 1000 kg / cm ² or more in an inert gas atmosphere such as argon, and the surface of the obtained HIP-treated body is subjected to surface grinding. Polishing is performed with diamond abrasive grains having an average particle size of 2 μm or less.

When a silicon carbide sintered body is manufactured by the method described above, a silicon carbide sintered body having an extremely smooth polished surface can be obtained.

[0019]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

(Examples 1 to 5) (1) Production of silicon carbide sintered body having polished surface Boron and carbon were added to silicon carbide powder (CMF-15H, manufactured by Taiheiyo Random Co., Ltd.) having an average particle size of 0.5 μm. Black was added in the amount shown in Table 1, mixed, dried and then sized. This powder was subjected to CIP molding at a pressure of 200 kg / cm ² , and then sintered under normal pressure at a temperature shown in Table 1 in an argon atmosphere. The obtained sintered body was further subjected to an argon atmosphere for 1 hour.
HI at a temperature of 700 ° C. and a pressure of 1200 kg / cm ²
P processed. The surface of the obtained HIP-treated body was ground with a surface grinder, and the surface was further polished with diamond abrasive grains having an average particle size shown in Table 1.

(2) Evaluation The surface roughness of the polished surface of the obtained sintered body was measured using a nano step (R).
The center line average roughness (Ra) was measured using an ank Taylor Hobson company (contact type, differential transformer type). Table 1 shows the results.

(Comparative Examples 1 to 6) For comparison, Comparative Example 1
In Comparative Example 2, except that the amount of boron added was smaller than that of the present invention, the fineness of the silicon carbide powder was smaller than that of the present invention. Except for roughening, in Comparative Example 4, except that the normal-pressure sintering temperature was higher than that of the present invention, in Comparative Example 5, except that the normal-pressure sintering temperature was lower than that of the present invention, in Comparative Example 6, the diamond grinding was performed. A silicon carbide sintered body having a polished surface was prepared and evaluated in the same manner as in Example 1 except that the fineness of the grains was coarser than that of the present invention. Table 1 shows the results.

[0023]

[Table 1]

As is evident from Table 1, in each of the examples, the polished surface had a surface roughness Ra of 2.1 nm or less and had an extremely smooth polished surface. This indicates that a sinter having satisfactory smoothness can be obtained only by polishing the surface of the sintered body without forming a silicon carbide film on the surface of the silicon carbide sintered body.

On the other hand, in Comparative Example 1, the addition amount of boron was too small, and in Comparative Example 2, the addition amount of carbon black was too large. In Comparative Example 4, the normal pressure sintering temperature is too high, and in Comparative Example 5, the normal pressure sintering temperature is too low. In Comparative Example 6, the fineness of the diamond abrasive grains is too coarse. Therefore, no satisfactory smoothness was obtained.

[0026]

As described above, according to the present invention, a silicon carbide sintered body having a smooth polished surface with extremely few pores having a center line average roughness (Ra) of 3 nm or less by a contact method can be obtained. As a result, silicon carbide sintering that can obtain an extremely smooth surface only by polishing, as a ceramic member used for parts in the semiconductor industry field that particularly dislikes dust and dust, or parts that can be used for industrial mirrors, etc. You can now provide your body.

Claims (2)

[Claims] 1. A polycrystalline silicon carbide sintered body, characterized in that the polished surface of the sintered body has a surface roughness of 3 nm or less as a center line average roughness (Ra) by a contact method. Silicon carbide sintered body. 2. A silicon carbide powder having an average particle diameter of 0.7 μm or less is added with 0.1 to 0.8% by weight of boron or a compound thereof as a sintering aid and 1 to 5% by weight of carbon. After sintering under normal pressure in an inert gas atmosphere at 1900 to 2050 ° C., it was further cooled to 1000 kg / cm.
Hot isostatic pressing (HIP) at a temperature lower than the sintering temperature under a pressure of ² or more, and polishing the surface of the obtained HIP-treated body with diamond abrasive grains having an average particle size of 2 μm or less. Production method of a silicon carbide sintered body.