JP2000273632A - Production of flat ceramic bulk material free from warpage by chemical vapor deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for producing a ceramic bulk material free from warpage by a chemical vapor deposition method. SOLUTION: The surface of a base material 3 in which ceramic is formed and deposited by a chemical vapor deposition method is subjected to spherical working, and in the case the thermal expansion coefficient of the material to be vapor-deposited is smaller than that of the base material 3, the shape by the shperical working is formed into the recessed one, and in the case the thermal expansion coefficient of the material to be vapor-deposited is higher than that of the base material, the shape by the spherical working is formed into the projecting one. The ceramic stock to be produced is desirably composed of silicon carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a warped ceramic bulk material by a chemical vapor deposition method.

[0002]

2. Description of the Related Art Conventionally, after forming a ceramic film such as silicon carbide on a surface of a base material by a chemical vapor deposition method (CVD method), the base material portion is removed by burning or mechanical processing. It was known to make ceramic materials such as silicon carbide. The ceramics thus obtained, particularly silicon carbide, have properties such as good thermal conductivity and have been used in semiconductor processes and the like. However, in such a method, when a substrate having a flat surface is used, when the material constituting the substrate and the formed ceramic material have different coefficients of thermal expansion, the ceramic after removing the substrate is removed. The material is
The phenomenon of warping outward or inward occurs. Therefore, in order to make the ceramic material flat, the coefficient of thermal expansion of the base material should be substantially the same as the coefficient of thermal expansion of the ceramic material, or a ceramic material thicker than the thickness of the final product should be made, and the material should be flat. Processing has to be performed, and there has been a problem that the utilization rate of the ceramic material is reduced and the production cost is increased.

As one method for eliminating the problem of the warpage of the product, when a silicon carbide material, for example, of the same material as the ceramic material formed on the surface of the base material is formed, the silicon carbide is formed on the surface of the base material. A coating layer of which the coefficient of thermal expansion of the base material and the coefficient of thermal expansion of the ceramic bulk material to be formed are made to match each other, specifically, the graphite base material is turned into silicon carbide by a chemical vapor reaction. Thus, a technique has been proposed in which the coefficient of thermal expansion of the base material is made to match the coefficient of thermal expansion of the ceramic to be formed (see JP-A-10-53464). As another method, a substrate made of a glassy carbon material is used as a substrate, and a ceramic coating layer such as silicon carbide is formed by a CVD method so as to cover both surfaces of the substrate. There has been proposed a method of manufacturing the ceramic bulk material by cutting the material in the horizontal direction at the center in the thickness direction including the material, that is, halving the material, and removing the base material portion from each of the halved products (particularly). See JP-A-10-167830). In the other method,
By using a glassy carbon material as the material of the substrate of the CVD method, the CVD method is used because of the denseness of the glassy carbon material
During the deposition of the ceramic by the method, the ceramic hardly penetrates into the base material, so that the base material and the formed ceramic layer only weakly adhere to each other. The substrate can be removed from the ceramic material simply by performing a cutting process such as cutting. This method is advantageous because it is not necessary to consider the thermal expansion coefficient of the material of the base material in relation to the thermal expansion coefficient of the ceramic material.

[0004]

However, in the prior art, the first method requires a chemical vapor reaction treatment of the base material, and the other method does not allow the deposited ceramic to penetrate, and the weak adhesion. Using a substrate made of a glassy carbon material that holds the deposited ceramic by force, it is intended to eliminate warpage due to stress in the ceramic due to the difference in thermal expansion coefficient between the substrate and the deposited ceramic. However, it has been found that during the formation and deposition reaction of ceramics by the CVD method, the strength of holding the deposited and formed ceramics is low, which is disadvantageous in terms of the stability of the deposited ceramics. An object of the present invention is to provide a method for producing a ceramic bulk material without instability during the formation and deposition reaction of ceramics by the CVD method and without warpage.

[0005]

SUMMARY OF THE INVENTION The present invention is based on an idea completely opposite to that of the above-mentioned other method. That is, the present invention relates to a method for obtaining a flat ceramic bulk material after removing a base material by using a stress generated by the difference in thermal expansion coefficient between the base material and a ceramic to be deposited and formed. That is, by using a substrate having a specific curvature, it is discovered that the ceramic bulk material after removing the substrate becomes a flat product, and a flat ceramic bulk material is obtained by using the principle. About the method. In order to obtain a flat ceramic product according to the above principle, after the formation and deposition of the ceramic on the surface of the substrate by the CVD method are completed, when the substrate is removed by ashing or the like, the ceramic is accumulated due to the difference in the thermal expansion coefficient. It has been found that this can be achieved by making the surface of the substrate on which the ceramic is formed and deposited a curvature related to said difference in thermal expansion coefficients, so that the stresses which result in the ceramic material as a flat product. Therefore, the present invention relates to the difference in thermal expansion coefficient between the base material and the formed ceramic material, so that the ceramic bulk material can be obtained as a flat product by simply burning and removing the base material. If the coefficient of thermal expansion of the material to be deposited is smaller than the coefficient of thermal expansion of the substrate, the surface of the substrate is spherically processed into a concave shape, and if the coefficient of thermal expansion of the deposited material is greater than the coefficient of thermal expansion of the substrate, the surface of the substrate is modified. This problem has been solved by forming a convex spherical surface.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The material constituting the substrate of the present invention is not limited to the material as described in the prior art, and the substrate is chemically treated as in the first method. There is no need. Therefore, a substrate having a desired curvature can be formed by using a static pressure forming method (CIP) or the like. Further, in the present invention, a high-purity silicon carbide layer having a constant thickness is formed by a heating reaction on the surface of a substrate having a curvature. However, the supply of a reactive gas when a conventional flat substrate is used is used. And a discharge means, and a carbon source, a compound simultaneously containing a silicon source and a carrier gas may be used as a raw material gas, or a carbon source and two kinds of compounds separately containing a silicon source. A carrier gas may be used. The heating temperature in the reaction vessel can be 1100 ° C. to 1500 ° C., and the pressure is desirably reduced to about 1 to 100 Torr. As the heating means,
For example, resistance heating, induction heating, infrared radiation heating, or the like can be used.

An embodiment of the present invention will be described below with reference to the drawings. As described in the above-mentioned prior art, the measurement of the warpage of the ceramic material is performed by measuring the distance of the obtained ceramic material from the horizontal surface and rising from the horizontal surface, and defining the distance as the amount of warpage (the maximum warpage amount). Only shown).

Example 1 A base material having a diameter of 200 mm × thickness of 5 mm, 50 to 4
A graphite base material having an average thermal expansion coefficient of 3.1 × 10 ⁻⁶ / ° C. at 00 ° C. was used. Since the thermal expansion coefficient of the formed silicon carbide chemical vapor deposition material is 3.5 × 10 ⁻⁶ / ° C., a substrate having an outwardly convex curved surface with a radius of curvature of about 6250 mm was formed. The substrate was loaded into the reaction vessel shown in FIG. 1, and a resistance heater was disposed opposite to the reaction vessel. The pressure in the reaction vessel was reduced to 300 Torr by a vacuum pump. Next, the heater was energized to set the temperature of the heater to 1300 ° C. Next, methyltrichlorosilane and hydrogen gas were supplied from the gas supply pipe for 1 hour.
The mixture was supplied at a rate of 5.5 liters / minute at a ratio of 100 to 100, and a silicon carbide vapor-deposited film (thickness of about 1 m
m) was formed. The substrate was removed by ashing treatment to obtain a silicon carbide material. The amount of warpage was 0.1 mm or less.

Example 2 As a substrate, a graphite substrate having a diameter of 200 mm × a thickness of 5 mm and a thermal expansion coefficient of 3.9 × 10 ⁻⁶ / ° C. was used. The thermal expansion coefficient of the formed silicon carbide chemical vapor deposition material is 3.5 ×
Since the temperature was 10 ⁻⁶ / ° C., a substrate having a concave curved surface with a radius of curvature of about 6250 mm was formed. The heating conditions, decompression conditions, and gas supply conditions were the same as in Example 1, and the thickness of the deposited film to be formed was almost the same as in Example 1. The substrate was removed by ashing treatment to obtain a silicon carbide material. The amount of warpage was 0.1 mm or less. Although only the case of silicon carbide is shown as a specific example, it is clear that the above method can be applied to the case of manufacturing other ceramic bulk materials.

[0010]

According to the method of the present invention, after forming a ceramic vapor-deposited film on a substrate surface by a CVD method, a flat ceramic bulk material without warpage can be obtained by simply removing the substrate by burning or the like. The excellent effect that it can do is brought.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an apparatus for producing a warped flat ceramic bulk material by a chemical vapor deposition method according to the present invention.

[Explanation of symbols]

1 reaction vessel 2 heater 3 substrate
4 Reaction gas 5 Exhaust

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuomi Horio 300 Aoyanagi-cho, Ogaki-shi, Gifu F-term in the Aoyagi Plant of IBIDEN Corporation (reference) 4G001 BA77 BB22 BC22 BC61 BD38 BE31 4G052 DB01 DB12 DC06 4K030 AA03 AA06 AA09 AA17 BA37 CA01 CA11 DA08 FA10

Claims (2)

[Claims] 1. The method according to claim 1, wherein the surface of the substrate on which the ceramic is formed and deposited by chemical vapor deposition is spherically processed, and when the coefficient of thermal expansion of the material to be deposited is smaller than the coefficient of thermal expansion of the substrate, the spherically processed surface is concave. A method for producing a warped ceramic bulk material by a chemical vapor deposition method, wherein the spherical processing is made convex when the coefficient of thermal expansion of the substance to be deposited is larger than the coefficient of thermal expansion of the substrate. 2. The method for producing a warped ceramic bulk material by a chemical vapor deposition method according to claim 1, wherein the produced ceramic material is silicon carbide.