JPH04130060A - Production of silicon carbide-based material - Google Patents

Abstract

PURPOSE:To easily obtain a high purity and high strength silicon carbide-based material suitable for a jig for producing a semiconductor by depositing carbon in a porous body of synthetic quartz glass by a vapor phase thermal decomposition method, calcining the porous body and filling metallic silicon into the open pores in the resulting porous preformed body. CONSTITUTION:A porous body of synthetic quartz glass is produced by a vapor phase synthesis method and worked into the shape of an end product. Carbon formed by thermally decomposing gas contg. gaseous hydrocarbon such as methane or gaseous halogenated hydrocarbon such as CH3Cl is deposited in the porous body by such an amt. as to regulate the molar ratio of carbon to silicon dioxide to >=3. The porous body is then calcined, and fused silicon is infiltrated into the resulting porous preformed body to fill metallic silicon into the open pores in the preformed body, and this silicon is allowed to react with excess carbon remaining in the body to obtain a silicon carbide-based material.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a silicon carbide material, and more particularly to a semiconductor manufacturing jig, such as a process tube used for thermal diffusion treatment of silicon wafers. , relates to a method for manufacturing a high-purity silicon carbide material useful as a material for heat-resistant jigs such as wafer ports.

Conventionally, heat-resistant jigs for semiconductor manufacturing, which require high purity, have mainly been made of quartz glass.

Quartz glass oil tools have the advantage that they can be easily manufactured with extremely high purity and are transparent, making it easy to observe the inside.

However, this quartz glass one begins to deform due to viscous flow at concentrations exceeding 1000'C, so
It could hardly be used for heat treatment at temperatures above 150°C, and it had the disadvantage of a short lifespan because it changed to α-cristobalite, devitrified, and broke.

On the other hand, as a material capable of solving these drawbacks, a composite material in which a porous silicon carbide molded body formed from silicon carbide powder is filled with metallic silicon has been developed and used. However, high-purity silicon carbide raw material powder is difficult to obtain, and the manufacturing process is complicated, including raw material blending, molding, purification treatment, firing, etc., and it also requires binders such as phenol resin, which can lead to contamination during the manufacturing process. It has been difficult to obtain a highly pure silicon carbide material due to impurities contained in the silicon carbide material.

In addition, as a method for impregnating a porous silicon carbide molded body with metal silicon, heating is performed above the melting point of metal silicon,
Method of penetrating molten silicon (Japanese Patent Application Laid-Open No. 51-85
374, Japanese Patent Application Laid-Open No. 64-14914, Japanese Patent Application Laid-open No. 1-115888, etc.) are generally used. In addition, a silicon impregnation method (see Japanese Unexamined Patent Application Publication No. 57-43553) has been proposed, in which a graphite heating element is induction heated to evaporate silicon, and a silicon carbide body is impregnated with the silicon.

Furthermore, a method has been proposed in which silicon carbide is vapor-deposited on the surface of a silicon carbide material to form a dense silicon carbide film to suppress the diffusion of impurities.

Problems to be Solved by the Invention Conventionally, silicon carbide materials used for semiconductor manufacturing have been produced by performing appropriate purification treatment after molding and firing. However, such purification treatment is contaminated during the complicated manufacturing process and is performed after firing into a dense sintered body, so impurity removal is limited to the surface layer of the sintered body. As a result, when a silicon carbide material jig manufactured by the above-mentioned conventional method is used to heat treat a silicon wafer, metal impurities such as Fe inside the silicon carbide material are diffused and released, contaminating the silicon wafer. was there.

In addition, the method of melting and vaporizing metallic silicon and impregnating it into a silicon carbide body requires a large amount of energy as it requires a high temperature of 2000'C or more, and there are also problems such as thermal distortion and cracking due to thermal shock etc. was there.

Furthermore, even in a method in which silicon carbide is vapor-deposited on the surface of a silicon carbide material to form a dense silicon carbide film to suppress the diffusion of impurities, this silicon carbide material has pinholes in the silicon carbide film on its surface. There were problems such as the occurrence of cracks due to mechanical and thermal shock due to the low adhesion strength of the silicon carbide film to the silicon carbide material.

The present invention was invented in view of the above-mentioned problems, and
Provides a method for producing a silicon carbide material that does not deform even under high temperatures, has high purity (and does not contaminate wafers during thermal diffusion treatment of silicon wafers, and is useful as a material for semiconductor manufacturing jigs. It is intended to.

In order to achieve the above object, the method for producing a silicon carbide material according to the present invention involves thermal decomposition of a gas containing hydrocarbon gas or halogenated hydrocarbon gas in a porous body of synthetic quartz glass. The method for producing a silicon carbide material described above is characterized by precipitating the carbon produced by the process and then filling the open pores of the porous molded body obtained by firing. The carbon deposited in the body is characterized by a carbon/silicon dioxide molar ratio of 3 or more.

Further, each of the above-mentioned methods for producing charcoal (arsenic material) is characterized in that surplus carbon remaining in the porous molded body is reacted and sintered with the filled metal silicon.

Furthermore, each of the above-described methods for manufacturing a silicon carbide material is characterized in that the metal silicon is filled into the open pores of the porous molded body by penetration of molten silicon.

Furthermore, in each of the first three methods for manufacturing silicon carbide materials described above, the filling of metallic silicon into the open pores of the porous molded body is characterized by thermal decomposition of a silicon-containing gas. .

The method for producing a silicon carbide material according to the present invention will be explained in more detail.

In the method according to the present invention, it is necessary to use the porous body of synthetic quartz glass as a starting material. This synthetic quartz glass porous body is composed of silicon dioxide fine particles with an average particle size of 0.01 to 10 μm, has a porosity of 40 to 80%, and has a high purity with a total impurity content of L ppm or less. Furthermore, since molding processes such as binder mixing and pressing are not required, there is no contamination during these processes. This porous body of synthetic quartz glass is processed into the shape of a final product and used as a starting material.

In the method according to the invention, a hydrocarbon gas or a halogenated hydrocarbon gas, for example CH4, C2H6CaHa,
C4H,. C2H4, C2H2, C2H4Cj2, CJ
aCQ3, C2H, Ci! .

At least one selected from C2H2Cg2, etc.
By heat-treating the porous body of synthetic quartz glass at a temperature above the decomposition temperature of the gas species used and below 1400°C in a gas atmosphere consisting of various kinds of gases, the inner surface of the porous body made of silicon dioxide fine particles is heated. Pyrolytic carbon having a particle diameter of about several nanometers is precipitated. At this time, carbon precipitation due to thermal decomposition does not occur below the decomposition temperature of the gas species used, and 14
At a temperature of 0.00°C or higher, the porous body of synthetic quartz glass becomes dense, making it impossible for carbon to be deposited inside.

The amount of carbon precipitated needs to be 3 or more in molar ratio to silicon dioxide in the porous body of synthetic quartz glass that is the base material. The reason is that the reaction between silicon dioxide and carbon is represented by SiO□13C-5iC+2CO(1),
When the amount of carbon precipitated is less than 3 in molar ratio, excess silicon dioxide remains, and this silicon dioxide becomes SiO during heat treatment.
It evaporates as a gas, and as a result, the shape of the porous body collapses,
This is because strength may be reduced or powdering may occur.

On the other hand, excess carbon remaining in the porous silicon carbide material reacts when impregnated with metal silicon and easily turns into silicon carbide.

Next, the synthetic silica glass-carbon composite is heated at 1600 to 2500°C under a non-oxidizing atmosphere, for example, under a gas atmosphere consisting of at least one selected from helium, neon, argon, hydrogen, etc., or in vacuum. Baking at temperature. As a result, the pyrolytic carbon ultrafine particles reduce the silicon dioxide fine particles extremely quickly, and the silicon dioxide fine particles are completely converted into silicon carbide. At this time, the firing temperature is 160°C because the reaction between silicon dioxide and carbon does not occur below 1600°C, and heating equipment that exceeds 2500°C is not practical.
A range of 0 to 2500°C is desirable.

Then, this porous molded body is impregnated with molten metal silicon to form a dense sintered body. At this time, the inside of the heating furnace is preferably kept under reduced pressure in order to quickly impregnate the molten silicon. Further, the heating furnace temperature needs to be higher than the melting point of metal silicon and at a temperature at which metal silicon does not evaporate.

Alternatively, the porous molded body made of silicon carbide may be used as a silicon-containing waste, for example, 5tCi! In a gas atmosphere consisting of at least one selected from 4.5tHC13, 5IHn, etc., at 2000°C above the decomposition temperature of the gas used.
By performing heat treatment at the following temperature, metallic silicon is deposited even into the interior of the porous molded body. Also,
Hydrogen, argon, etc. may be used as a carrier gas.

At this time, precipitation of metallic silicon does not occur below the decomposition temperature of the gas species used, and at temperatures exceeding 2000°C, large amounts of energy are required and uneven precipitation occurs near the surface of the porous molded body. More preferably,
Although it varies depending on the type of gas used, 600 to 1200°
It is preferable to process under mild conditions of C.

In addition, at this time, since the excess carbon present in the silicon carbide porous molded body is very fine particles of several nanometers in size, it is easily converted into silicon carbide by molten silicon, silicon-containing gas, or precipitated metallic silicon. The strength of silicon carbide materials is improved.

Sakuei VAD (~1apor-phase Axial
Deposition) Vapor-phase synthetic quartz glass produced by irradiation, etc. has extremely high purity with a total metal impurity content of less than 1 ppm, and is porous, so it can be heated in a carbon-containing gas atmosphere to form synthetic quartz glass. It is possible to deposit carbon even inside the porous body.

Furthermore, by setting the carbon precipitated in the porous body of synthetic quartz glass to a carbon/silicon dioxide molar ratio of 3 or more, silicon dioxide remains, and this silicon dioxide becomes Si during heat treatment.
It volatilizes as O gas, and as a result, the porous body does not lose its shape, lose strength, or become powder.

Furthermore, by firing the silicon dioxide-carbon composite obtained by the above heat treatment, a porous silicon carbide molded body or a silicon carbide-carbon porous molded body with extremely high purity can be obtained.

Next, this porous molded body is heated to a temperature higher than the melting point of metal silicon, and is immersed in molten silicon under vacuum for reaction sintering, thereby easily obtaining a dense silicon carbide material.

Alternatively, instead of using molten silicon, by heat-treating the porous molded body in a silicon-containing gas atmosphere, it is possible to cause metallic silicon to come out even to the inner surface of the porous molded body. be. When excess carbon exists inside the porous molded body, it quickly reacts with the metal silicon to form silicon carbide, and the strength of the silicon carbide material is improved.

According to the above method, it is possible to omit the steps such as crushing, mixing, and molding of raw materials, which are essential in conventional methods, and it is possible to avoid contamination in these processes, resulting in extremely high purity silicon carbide materials. It will be done.

EXAMPLE 2 Examples of the method for manufacturing a silicon carbide material according to the present invention will be described below.

[Example 1] Synthesized by VAD method, bulk density is about 0.3 g/cm
3.Specific surface area is approximately 12m2/g, average particle diameter is 02μm
A synthetic quartz glass porous body was treated in an atmosphere of 100% methane gas at a temperature of 1000°C for 4 hours to produce a synthetic quartz glass porous body-carbon composite with a molar ratio of silicon dioxide and carbon of about 85. I got it.

Then, this composite was incubated under vacuum at a temperature of 2000°C for 3
After baking for an hour, the bulk density was about 0.8g/cm3. A porous molded body, which is a porous silicon carbide-carbon composite having a porosity of about 46% and a molar ratio of silicon carbide to carbon of about 5.5, was obtained.

This porous molded body was inserted into a graphite crucible coated with silicon carbide, and a lump of metallic silicon with a purity of 1ON was placed around it and heated to 1600°C, and the molten silicon was poured into the open pores of the porous molded body. infiltrated into.

Table 1 shows the density and bending strength of the silicon carbide material obtained, and Table 2 shows the metal impurity concentration.

Summer Shonin Release (Unit: ppm) [Comparative Example 1] When similar synthetic quartz glass was treated at a temperature of 1000°C for 1 hour in an atmosphere of 100% methane gas, silicon dioxide and carbon were removed. A composite of porous synthetic quartz glass and carbon having a molar ratio of about 2.3 was obtained.

This composite was then incubated under vacuum at a temperature of 2000°C for 3
When treated for a period of time, it became powdered silicon carbide, making it impossible to impregnate it with silicon.

[Comparative Example 2] The purity of the silicon carbide material for semiconductors manufactured by the conventional method is also listed in the above Table 2 for comparison.

[Example 2] Synthesized by VAD method, bulk density is about 0.5g7cm
3. Specific surface area is about 10m27g, average particle size is about 02u
A porous body of synthetic quartz glass of m was subjected to carbonization treatment at a temperature of 900°C for 4 hours in an atmosphere of 100% methane gas,
A composite of porous synthetic quartz glass and carbon in which the molar ratio of carbon to silicon dioxide was about 65 was obtained.

Next, this composite was fired under vacuum at a temperature of 1800°C for 3 hours, and the bulk density was about 0.9 g/cm3, the porosity was about 32%, and the molar ratio of carbon to silicon carbide was about 3. A silicon carbide-carbon composite (porous molded body) No. 5 was obtained.

Next, the porous molded body was placed in an electric furnace equipped with a reaction tube made of quartz glass, and 5IHCj3 gas was added at 10voj%.
In a mixed gas atmosphere containing 90 voj% H2 gas, 100
It was treated at a temperature of 0°C and converted into silicon carbide by dinocon, which precipitated excess carbon. Through this treatment, it was possible to obtain a dense silicon carbide material in which silicon penetrated into the interior.

Table 3 shows the density and bending strength of the silicon carbide material obtained, and Table 4 shows the concentration of metal impurities contained therein.

According to the method for manufacturing silicon carbide material 4 according to this example, the bulk density is 2.97 g/cm3. Apparent porosity is 0
．． 82voj%, average bending strength 48.2kgf/mm
2, high strength was obtained, and all impurities were lppm.
An unprecedented high purity silicon carbide material was obtained.

[Comparative Example 3] A similar porous body of synthetic quartz glass was made of 100% methane glass.
When the mixture was treated in an atmosphere of 900° C. for 1 hour, a porous synthetic quartz glass-carbon composite having a molar ratio of silicon dioxide to carbon of about 17 was obtained. Then, when this composite was subjected to a firing treatment under vacuum at a temperature of 1800° C. for 3 hours, it became powdered silicon carbide, and it was impossible to impregnate it with metallic silicon as a subsequent step.

[Comparative Example 4] Silicon carbide powder was molded and fired using an organic binder, and the resulting porous silicon carbide was impregnated with molten dinocon to produce a silicon carbide material.

The density and bending strength of this silicon carbide material are shown in Table 3, and the purity is shown in Table 4. Bulk density is 3.02g/
cm3. The silicon carbide material had an apparent porosity of 0.31 vog%, an average bending strength of 24.8 kgf/mm2, relatively low strength, and a high content of impurities.

(Unit: ppm) As is clear from the above explanations, the method for manufacturing a silicon carbide material according to the present invention uses semiconductor manufacturing jigs, such as thermal diffusion treatment of silicon wafers, etc. It is possible to produce a high-purity, high-strength silicon carbide material suitable for manufacturing heat-resistant jigs such as process tubes and wafer boats used in

Special permission Out wish Man Sumitomo Metal Industries Co., Ltd. teenager Reason People/patent attorneys Ryu Iuchi

Claims (5)

[Claims] (1) Carbon produced by thermal decomposition of a gas containing hydrocarbon gas or halogenated hydrocarbon gas is deposited in a synthetic quartz glass porous body, and then fired into the open pores of the porous molded body obtained. A method for producing a silicon carbide material, characterized by filling it with metallic silicon. (2) The method for producing a silicon carbide-based material according to claim 1, characterized in that the carbon precipitated in the synthetic silica glass porous body has a carbon/silicon dioxide molar ratio of 3 or more. (3) The method for producing a silicon carbide material according to claim 1 or 2, characterized in that surplus carbon remaining in the porous molded body is reacted and sintered with the filled metal silicon. (4) The silicon carbide material according to any one of claims 1 to 3, wherein the metallic silicon is filled into the open pores of the porous molded body by penetration of molten silicon. Method of manufacturing the material. (5) The carbonization according to any one of claims 1 to 3, wherein the metal silicon is filled into the open pores of the porous molded body by thermal decomposition of a silicon-containing gas. A method for producing a silicon material.