JPS62265172A - Method for manufacturing silicon carbide sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to silicon carbide sintered bodies, particularly silicon carbide, which has excellent electrical insulation and thermal conductivity and is useful as IC substrates, electronic materials, etc. This relates to unglazed sintered bodies.

(Prior art) Silicon carbide sintered bodies are used for various purposes due to their excellent heat resistance, abrasion resistance, strength, and corrosion resistance. What I have is I
Used for C substrates, electronic materials, etc.

However, it is technically difficult to improve the resistivity and thermal conductivity of this silicon carbide sintered body, and there are known methods for this, such as adding beryllium oxide; Because it is highly toxic, there are various problems with its handling, including safety control during the manufacturing process.Beryllium oxide has a small sintering promotion effect, so atmospheric pressure sintering is required to obtain a good sintered body. It cannot be used and must be hot press sintered.Furthermore, in order to make IC boards from now on, it is necessary to slice and polish this sintered body, which poses a cost problem.Beryllium oxide However, there are concerns about supply due to low production worldwide.
It also has the disadvantage of being expensive.

On the other hand, aluminum oxide is widely used for ceramic IC substrates because it is inexpensive, but it has a thermal conductivity of 20 W/m and a thermal expansion coefficient of 8 x 10"6/℃. The coefficient of thermal expansion of silicon single crystal is 3
．． 5 x 10-'/''C, there is a need to provide a high heat dissipation material to replace it. In addition to silicon carbide, aluminum nitride is also known as this high heat dissipation material, but nitride Aluminum has the inherent disadvantage of poor thermal conductivity and poor chemical resistance, which greatly limits its range of applications.

(Structure of the Invention) The present invention relates to a method for producing a silicon carbide sintered body having excellent electrical insulation and thermal conductivity without using beryllium oxide, which has the disadvantages described above. 0.1 to 5% by weight of boron or a boron compound as a sintering aid is added to the fine powder, and the molded body is molded under pressure. It is characterized by being sintered in an incinerator under coexisting conditions.

That is, the present inventors have conducted various studies on obtaining a silicon carbide sintered body that has excellent electrical insulation and thermal conductivity and is therefore useful for IC substrates, electronic materials, etc., and has found that, for example, silane The sintered body obtained by sintering silicon carbide powder obtained by a gas phase pyrolysis reaction in the coexistence of boron nitride and/or boron oxide has excellent electrical insulation and thermal conductivity. For example, this has an electrical resistivity of 1011~13Ω0 and an electric resistivity of 150~22Ω.
It exhibits a thermal conductivity of 0 W/m, and this sintering can be done under normal pressure, and no toxic substances are added to the manufacturing process.
According to this, it was discovered that the target product could be easily mass-produced at low cost, and the boron nitride used in
The present invention was completed by conducting research on the type of boron oxide, the amount added, the sintering method, etc.

In the method of the present invention, if the particle size of the silicon carbide powder used as the starting material is too large, sintering will be difficult, so the average particle size should be 0.
．． It is best to use a fine powder of about 01 to 3 μs.
In addition, since it is better to have the purity as high as possible, methylhydrodiene silane having the formula %2b+2), such as tetramethyldisilane, which has been purified by distillation in advance, is mixed in a carrier gas with a concentration of 750 to 1,600. A method of vapor phase pyrolysis at
0-46912)). The silicon carbide obtained by this vapor-phase thermal decomposition method of methylhydrogensilane has a high surface activity, and is an aggregate of fine particles with crystallites of 50 Å or less, and has a spherical shape with an average particle size of 0.01 to 1 μm. Ultrafine particle β
Since it is silicon carbide, there is no need for a pulverization process to further refine it, and since the starting material, methylhydrogensilane, has been highly purified through rectification, it is extremely pure. It is obtained as a high value.

In the method of the present invention, first, boron or a boron compound as a sintering aid is added to this fine silicon carbide powder.
Sintering is carried out in the presence of boron nitride and/or boron oxide, and the boron or boron compound added to the silicon carbide fine powder is known as a sintering aid for silicon carbide. Therefore, examples of this boron compound include boron carbide, titanium boride, boron oxide, etc., but the amount of boron or boron compound added is 0.1% by weight or less calculated as boron content. If it is 5% by weight or more, a high-density sintered body can be obtained, but this sintered body will have low resistivity, so 0.1 to 5% by weight. It needs to be within the range of In addition,
This mixture of silicon carbide and boron or a boron compound is molded under pressure and used as a molded body in the next sintering step.

On the other hand, boron nitride and boron oxide, which are present during the sintering of the silicon carbide aggregate to which boron or boron compounds are added, are used to impart electrical insulation to the silicon carbide sintered viscous body. All of these are commercially available,
For example, boron nitride may be either hexagonal or cubic, and there is no significant difference between them.However, both boron nitride and boron oxide are used to increase the resistance of silicon carbide sintered viscous materials. Since it is a boron nitride and/or boron oxide, it is preferably of high purity, and therefore, it is preferable to have a purity of 99% or more. Note that this boron nitride and/or boron oxide may be used as a powder. However, when sintering silicon carbide aggregates, the powder may scatter when replacing the air in the furnace, introducing inert gas, or performing vacuum treatment, which may cause equipment failure. Therefore, it is preferable to use this product as a molded body or a sintered body.

The production of a sintered silicon carbide viscous body by the method of this invention involves adding a molded body of silicon carbide fine powder to which boron or a boron compound as a sintering aid is added, in the coexistence of boron nitride and/or boron oxide. Although the reaction mechanism is unknown, a silicon carbide aggregate containing boron or a boron compound is sintered in the vicinity of boron nitride,
The presence of a high-resistivity agent such as boron oxide increases the resistance and obtains a sintered body with improved thermal conductivity. This sintering is preferably carried out under vacuum or under an inert gas atmosphere such as nitrogen, helium, or argon to obtain a sintered body with excellent physical properties. Since it contains a boron compound, there is no need to use a hot press, and it can be sintered under atmospheric pressure.The sintering temperature is 1,800 ℃.
``If the temperature is below C, the sintered body obtained will not have a high density,
2. If the temperature is higher than 200°C, abnormal grain growth of silicon carbide will occur, resulting in a sintered body with low electrical resistance and low strength. It is better to

Since the silicon carbide sintered viscous body obtained by the method of the present invention is sintered in the presence of boron nitride and/or boron oxide, the sintered body without such treatment has a resistivity of 104~@ Ωl, while the resistivity is 1012~1
It has a high resistance of 3Ω, and its thermal conductivity is 150 to 220W/K, so it is suitable for IC.
It is said to be particularly useful as substrates and other electronic materials.

Next, examples of the present invention will be given, and the thermal conductivity in one example is the result of measurement using the xenon flash method.

Example 1 Inner diameter 50IIIm, length 1. OOOwm (7) A vertical tubular electric furnace equipped with a quartz core tube is heated to 1.200°C,
Next, hydrogen gas containing 5% by volume of tetramethyldisilane ((CH3)4Si2H2) was introduced into diN at a rate of 1.0OOcc/min for gas phase thermal decomposition, resulting in ultrafine particles of silicon carbide. It was confirmed from the X-ray photograph that this was an aggregate with 25 crystallites, an average particle size of 0.2p, and a specific surface area of 37.3m/H.

Next, add 0.0 g to 14.955 g of this silicon carbide fine powder.
45 boron (0.3%) was added, and this mixture was put into a mold and formed into a disc shape of 10 IIaφ x 1 cabinet, and pressurized to 1.5 tons/d with a rubber press to form 5 pieces of boron. A molded body A was made.

Separately, hexagonal boron nitride (manufactured by Shin-Etsu Chemical Co., Ltd.) Ig was molded and pressurized in the same manner as above to form 1oanφ.
Five disc-shaped molded bodies B with a diameter of 1 mm were made.

Next, the molded bodies A and B were placed alternately in an electric sintering furnace, and after replacing the inside of the furnace with an argon gas atmosphere, they were sintered at 2,050°C under atmospheric pressure for 30 minutes. However, compact B did not sinter, but compact A became a sintered compact, so after polishing the surface of this sintered compact, its density,
Electrical resistivity.

When the thermal conductivity was measured, the results shown in Table 1 were obtained.

Table 1 Examples 2 to 7 The amount of boron added as a sintering aid in Example 1 was as shown in Table 2, or the boron was replaced with the boron compound shown in Table 2. The rest was treated in the same manner as in Example 1, and the physical properties of the obtained sintered body were as shown in Table 2.

Example 8 Boron oxide powder (manufactured by Hyozan Yakuhin Co., Ltd.) Ig was placed in a mold and molded and pressurized in the same manner as in Example 1 to form a 10mm diameter x 1mm piece.
05 disc-shaped molded bodies were made.

Next, this compact C and the compact A made in Example 1 were placed alternately in an electric sintering furnace, sintered under the same conditions as in Example 1, and then cooled. A sintered body was obtained, and after polishing the surface, its physical properties were measured, and the results shown in Table 3 were obtained.

Table 3 Examples 9 and 10 As silicon carbide collector powder, β-type silicon carbide manufactured by IBIDEN Co., Ltd. with a specific surface area of 16 m/g and a specific surface area of 11 rrr/g were used.
g of α-type silicon carbide manufactured by Showa Denko K.K. was used, boron and carbon were added as sintering aids to 14.7 g of these in the amounts shown in Table 4, and the same procedure as in Example 1 was carried out. A molded body E was prepared by processing the molded body E, and when these were sintered in the presence of the molded body B in the same manner as in Example 1, the physical properties of the obtained sintered body were as shown in Table 4. The results were obtained.

Comparative Example 1 In Example 1, molded body A was sintered in the same manner as in Example 1 without the presence of molded body B, and the physical properties of the obtained sintered body were measured, as shown in Table 5. The results were as expected, and although an increase in density was observed, the electrical resistivity was low.

Table 5

Claims (1)

[Claims] 1. A molded body obtained by adding 0.1 to 5% by weight of boron or a boron compound as a sintering aid to silicon carbide fine powder and molding it under pressure. A method for producing a silicon carbide sintered body, comprising sintering it in a sintering furnace in the coexistence of boron nitride and/or boron oxide. 2. The method for producing a sintered silicon carbide body according to claim 1, wherein the silicon carbide fine powder is obtained by a gas phase pyrolysis method of a methylhydrogensilane compound. 3. The method for producing a silicon carbide sintered body according to claim 1, wherein the boron compound is boron carbide, titanium boride, or boron oxide. 4. The method for producing a silicon carbide sintered body according to claim 1, wherein the sintering is carried out at a temperature of 1,800 to 2,200° C. in a vacuum or under atmospheric pressure in an inert gas atmosphere.