JPH0665628B2 - Method for producing porous silicon carbide material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a porous silicon carbide material having conductivity used as an electrode for a plasma etching apparatus.

[Conventional technology]

As a method for producing a porous silicon carbide material having conductivity, a method has been proposed in which the surface of a silicon carbide particle is coated with a carbonizing resin to be molded, the carbonizing resin is carbonized, and then molten metal silicon is infiltrated. There is.

In this method, the amount of molten metallic silicon to be infiltrated is defined as an amount of about 2.5 times the amount of organic carbide and the amount of unreacted silicon that is 2% by weight or more of the entire material.

[Problems to be Solved by the Invention]

The amount of unreacted silicon has a great influence on the electrical and mechanical properties of the finished material, and the optimum amount varies depending on the size of the aggregate particles used and the density of the compact. Known to be.

Therefore, in the production of a new product, there is no choice but to adopt a method in which samples with different molten metal infiltration amounts are prepared, the characteristics of each sample are measured, and the optimum value of the molten metal silicon infiltration amount is determined. No, it requires extra materials and man-hours.

An object of the present invention is to solve the above-mentioned problems, to coat the surface of a silicon carbide particle with a carbonizing resin, to mold the carbonized resin, and then to electrically and mechanically infiltrate molten metal silicon. It is an object of the present invention to provide a method capable of extremely easily setting the infiltration amount of molten metal silicon for obtaining a porous silicon carbide material having excellent dynamic characteristics.

[Means for Solving the Problems]

As a result of earnest research to solve the above problems, the gas permeability, material strength, and electric resistance, which are important characteristics of the material, change in the characteristic values with a certain amount of molten metal silicon infiltration amount as a boundary. Was found to be smaller.

The change in these properties is due to the amount of unreacted silicon in the material.

Then, it was found that the amount of unreacted silicon in the material at the inflection point where the change in each characteristic becomes small and the amount of micropores of the compact of the aggregate measured by the mercury porosimeter match.

The present invention has been achieved based on the above findings, and a method for producing a porous silicon carbide material in which silicon carbide particles are used as an aggregate and molten metal silicon is infiltrated into a molded body of the aggregate as a binder of the aggregate. In the above, the amount of molten metal silicon to be infiltrated as the binder is obtained by the cumulative pore volume of micropores having a predetermined pore diameter or less in the aggregate formed body, that is, the aggregate formed body (molten metal The amount of micropores (before infiltration of silicon) was measured by a mercury porosimeter, and the amount of silicon added to convert the organic carbide in the raw material mixture into silicon carbide was added to the molten metal silicon. The infiltration amount of

[Action]

The present invention measures the micropores of a molded body of an aggregate by means of a mercury porosimeter or the like, and the amount of the micropores obtained by this measurement and the amount of the organic carbide in the raw material mixture necessary for silicon carbide conversion The amount can be calculated.

Therefore, in order to obtain the optimum infiltration amount of molten metal silicon, it is possible to obtain the infiltration amount of the molten metal without producing a large number of samples with different silicon infiltration amounts and measuring the characteristics,
This makes it possible to easily and reliably manufacture a porous silicon carbide material having excellent electrical and mechanical properties.

〔Example〕

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

Example 1 A carbonization rate of 5 was obtained on the surface of silicon carbide particles having an average particle size of 100 μm.
90 parts by weight of 0% by weight phenolic resin is coated on 10 parts by weight of silicon carbide particles and molded, and the resin is carbonized in a vacuum at 1500 ° C. for 2 hours to obtain a molded body of aggregate having a bulk density of 1.9 g / cm ^3. It was created.

FIG. 1 shows the results of pore measurement of this molded product using a mercury porosimeter.

There are two types of pores, macropores and micropores, and the cumulative pore volume when the micropores have a pore diameter of 10 μm or less as shown in FIG. 1 is about 0.032 cc / g, The amount of micropores per 1cc of molded product of micropores is 0.0
32 cc / g × 1.9 g / cm ³ (bulk density) = 0.06 cc / cc.

Next, a sample in which different amounts of molten metallic silicon were infiltrated into this molded body having a bulk density of 1.9 g / cm ³ was prepared, and the air permeability, bending strength, and electric resistance were measured. The relationship with the amount of unreacted silicon was determined.

The molten metal silicon was infiltrated by dispersing the metal silicon powder in water to form a paste, applying a required amount on the surface of the molded body, drying it, and then heat-treating it in a vacuum furnace at 1500 ° C. for 2 hours in a vacuum atmosphere.

The amount of unreacted silicon was calculated by measuring the apparent density and bulk density of the material after the heat treatment and using the values from the following equation (1).

Unreacted Silicon Amount ST ( ^cc / _cc ) = BD × [(3,647 / AD) -1,136] ...
(1) BD: High Density After Silicon Infiltration AD: Apparent Density After Silicon Infiltration First, FIG. 2 shows the relationship between the air permeability and the amount of unreacted silicon.

As is clear from FIG. 2, when the amount of unreacted silicon exceeds the amount of micropores of 0.06 ^cc / _cc shown in FIG. 1, the air permeability sharply decreases.

Next, the relationship between the bending strength and the amount of unreacted silicon is shown in FIG.
The relationship between the electrical resistance and the amount of unreacted silicon is shown in FIG.

As is clear from FIGS. 3 and 4, the inflection point is 0.06 ^cc / _{cc of} unreacted silicon in all cases, and all the characteristics are in agreement with the micropore amount obtained by the mercury porosimeter. ing.

Example 2 A carbonization rate of 5 was obtained on the surface of silicon carbide particles having an average particle diameter of 100 μm.
90 parts by weight of 0% by weight phenolic resin is coated on 90 parts by weight of silicon carbide particles and molded, and the resin is carbonized in a vacuum at 1500 ° C. for 2 hours to mold an aggregate having a bulk density of 2.0 g / cm ^3. Created the body.

The micropore amount of this molded product was measured by a mercury porosimeter.

As shown in FIG. 5, when the pore size of the micropores is 10 μm or less, the cumulative pore volume is about 0.042 cc / g. Therefore, the micropore amount per 1 cc of the micropores is
0.042cc / g × 2.0g / cm ³ (bulk density) = 0.0
It becomes 84cc / cc.

In addition, the amount of silicon required to convert 1 g of carbon into silicon carbide is 28
/ 12 g (equimolar reaction), and the amount of silicon necessary for converting the organic carbide in 1 g of the molded body into silicon carbide is determined by the following formula.

[(10 × 0.5) / (90 + 10 × 0.5)] × 28/12 = 0.0123 g where 10 is the amount of phenol resin, 0.5 is the carbonization rate, and 90 is the amount of silicon carbide particles. .

Further, the weight of silicon of 0.042 cc was 0.042 × 2.33 = 0.098 g, and a sample was prepared so that the total amount of silicon infiltration was 0.123 + 0.098 = 0.22 g. .

For comparison, samples having a silicon infiltration amount of 0.20 g and 0.24 g were also prepared and the characteristics of the three were compared. The results are shown in Table 1.

As is clear from Table 1, a silicon infiltration amount of 0.22 g (Example) shows the most suitable characteristics as a conductive porous silicon carbide material used as an electrode for a plasma etching apparatus. There is.

In addition, in the above-mentioned examples, an example in which the pore distribution of the aggregate formed body is measured by a mercury porosimeter has been shown, but in addition to this, methods such as microscopic observation and measurement of the pore distribution by the BET multipoint method are also performed. It is also possible to measure the pore size distribution of the molded body of aggregate.

〔The invention's effect〕

As described above, it becomes possible to easily set the optimum infiltration amount of metallic silicon, which was determined experimentally by making a sample, by measuring the amount of micropores in the molded body in advance, and Raw materials and manufacturing time in the production of silicon carbide can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a graph showing the results of pore measurement by a mercury porosimeter of the molded body in Example 1, FIG. 2 is a graph showing the relationship between the air permeability and the amount of unreacted silicon, and FIG. 3 is the bending strength and unreacted silicon. FIG. 4 is a graph showing the relationship between the electric resistance and the amount of unreacted silicon, and FIG. 5 is a graph showing the results of pore measurement by the mercury porosimeter of the molded body of Example 2.

Claims (2)

[Claims] 1. A method for producing a porous silicon carbide material in which silicon carbide particles are used as an aggregate and molten metal silicon is infiltrated as a binder of the aggregate into a molded body of the aggregate, in which a melt is infiltrated as the binder. A method for producing a porous silicon carbide-based material, characterized in that the amount of metallic silicon is determined by a cumulative pore volume of micropores having a predetermined pore diameter or less in a molded body of aggregate. 2. The amount of micropores of 10 .mu.m or less in the molded body of the aggregate is measured by a mercury porosimeter, and the amount of this micropore is the metallic silicon necessary for converting the organic carbide in the raw material into silicon carbide. The method for producing a porous silicon carbide-based material according to claim 1, wherein an amount obtained by adding the amounts is set as an infiltration amount of the molten metal silicon.