JPH0733579B2 - Member having SiC coating and method for forming SiC coating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a member having a SiC coating and a method for forming the SiC coating, and more particularly to a SiC coating having improved adhesion between a polysilicon substrate and the SiC coating. The present invention relates to a member and a method for forming a SiC coating.

[Prior Art] In recent years, as high-temperature and high-strength materials, non-oxide ceramics such as silicon nitride, silicon carbide and sialon, or so-called new ceramics such as aluminum oxide and zirconium oxide have been rapidly focused on, and many researches and developments have been made. Has been done.

Among these ceramics, silicon carbide (hereinafter abbreviated as “SiC”) is a light material.

 High mechanical strength and stability from room temperature to high temperature.

Excellent in spalling resistance due to small thermal expansion and good thermal conductivity.

 Extremely high corrosion resistance.

 High hardness and excellent wear resistance.

It has conductivity and can be used as an electric element. It has characteristics such as the following, and is attracting attention as an extremely important industrial material.

Above all, SiC produced by a vapor phase method such as a CVD method is
Since these properties are remarkably high because they are dense and highly pure, a method for improving the properties of various members by coating with a vapor-phase method SiC film has been conventionally proposed.

[Problems to be Solved by the Invention] However, when a high-purity SiC film is formed on the surface of a base material by a vapor phase method, when there is a large difference in thermal expansion coefficient between the base material and the film, film peeling or cracking occurs. There is a problem of occurrence.

Therefore, in the past, isotropic carbon is limited to sintered SiC as a material capable of forming a SiC coating film.
For example, in existing polysilicon wafer boats used in semiconductor diffusion furnaces, SiC and SiC
No film could be formed.

[Means for Solving Problems] The present invention is intended to solve the problems of film peeling and cracking that occur when a SiC film is formed on the surface of a substrate such as a polysilicon wafer boat. A member in which a coating film containing SiC and Si is formed on a silicon base material, and the SiC content in the coating film is increased as the coating material surface is separated from the surface of the polysilicon base material.
A member having a SiC coating characterized by consisting of only a silicon raw material gas and a small amount of a carbon raw material at the initial stage when SiC is deposited by flowing a silicon raw material gas and a carbon raw material gas on a polysilicon substrate. A silicon raw material gas containing gas is flowed to deposit only Si or a Si layer containing a small amount of SiC, and then the proportion of carbon raw material gas is sequentially increased to increase the SiC deposition rate, and only SiC is deposited at the end. The gist is a method for forming a SiC film, which is characterized by the above.

[Operation] Since the SiC coating of the member of the present invention contains SiC and Si, the SiC content in the coating is increased as it is separated from the surface of the polysilicon substrate, and the coating surface is composed of only SiC. Although the surface is high-performance SiC, the polysilicon substrate does not directly contact with SiC but contacts Si or a composite layer consisting of Si and a small amount of SiC. Therefore, the difference in coefficient of thermal expansion between the polysilicon base material and the coating film is small. Then, the thermal expansion coefficient of the coating, from the contact surface side of the polysilicon substrate, gradually approaches the thermal expansion coefficient of SiC in the thickness direction thereof, so that the problem of film peeling or cracking due to the difference in thermal expansion coefficient occurs. Will be resolved.

Thus, in this way the SiC content changes in the thickness direction
A film containing iC and Si is formed by flowing a silicon source gas and a carbon source gas on a polysilicon substrate according to the method of the present invention.
When depositing SiC, in the initial stage, a silicon raw material gas or a silicon raw material gas containing a small amount of carbon raw material gas is flowed.
It is easily formed by depositing a Si layer containing only Si or a small amount of SiC, then sequentially increasing the proportion of the carbon source gas to increase the proportion of depositing SiC, and finally depositing only SiC. According to such a vapor phase method, it is possible to deposit a layer in which Si and SiC are extremely uniformly dispersed, which is advantageous for forming a Si-SiC composite layer inside the coating film.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a partial cross-sectional view of a member having a SiC coating according to an embodiment of the present invention. As shown in the figure, the member having the SiC coating of the present invention is a member in which the coating 2 containing SiC and Si is formed on the polysilicon base material 1, and the SiC coating is separated from the surface of the polysilicon base material in the coating. The SiC content of is increased, and the coating surface is made of only SiC.

That is, the coating film 2 according to the present invention shows that the ratio of the distance d from the polysilicon substrate 1 at a certain point in the coating film to its thickness d ₀ , that is, d / d ₀ approaches 1 The SiC content ratio (mol%) approaches 100, and finally provides the SiC coating surface.

The rate of increase of the SiC content ratio with respect to d / d ₀ is not particularly limited, and may be one that increases proportionally as shown in FIG. 2 or one that follows such an increase curve.

Further, the surface of the coating film 2 in contact with the polysilicon substrate 1, that is, the layer at the part of d / d ₀ = 0 is a composite layer of Si and SiC containing a small amount of SiC even if it is a single layer of Si. It may be. Further, the layer of SiC on the surface of the coating film 2 may have a certain thickness. Therefore, it may follow an increasing straight line of the SiC content ratio with respect to d / d ₀ as shown in FIG. 3 or a similar increasing curve.

Such a SiC coating according to the present invention, according to the method of the present invention, when flowing a silicon raw material gas and a carbon raw material gas on a polysilicon substrate to deposit SiC, initially only a silicon raw material gas or a small amount of A silicon raw material gas containing a carbon raw material gas is flowed to deposit Si only or a Si layer containing a small amount of SiC, and then the proportion of the carbon raw material gas is sequentially increased to increase the SiC deposition rate. By precipitating, it can be formed easily and efficiently.

For example, at least the film forming part of the polysilicon substrate is CV
D Reaction temperature region, for example, heated to 1050-1250 ℃, H ₂ / SiCl _{4 is made} to flow initially as a CVD source gas, and a Si layer is formed to a desired thickness by the reaction of SiCl ₄ + 2H ₂ → Si + 4HCl. C ₃ H ₈ is mixed into this raw material gas, and the proportion of C ₃ H ₈ is gradually increased to produce Si.
A mixed layer of Si and SiC in which the C content gradually increases is formed to a desired thickness, and finally a SiC layer having a desired thickness is formed with a gas composition of SiCl ₄ / C ₃ H ₈ .

According to such a gas phase reaction, the composite layer of SiC and Si deposited between the Si layer and the SiC layer is a uniform dispersion of SiC and Si, and excellent film characteristics can be obtained. . In addition,
In the present invention, various materials other than the above may be used as the silicon source gas and the carbon source gas.

INDUSTRIAL APPLICABILITY By applying the present invention to a polysilicon wafer boat or the like, its heat resistance and mechanical strength can be improved and durability can be remarkably increased.

[Effects of the Invention] As described in detail above, the member having the SiC coating of the present invention has a SiC layer on the surface, and therefore has excellent corrosion resistance and wear resistance of SiC.

Si or SiC containing a small amount of Si or SiC on the side of the coating that contacts the substrate
Since it is a composite layer of, the difference in thermal expansion between the base material and the coating film is relaxed.

Since the SiC content in the coating increases as the distance from the substrate surface increases, and the coating surface is made of only SiC, a large thermal expansion difference does not occur in the coating.

Therefore, a member having a high-characteristic SiC coating formed on the surface of a polysilicon substrate without causing problems such as film peeling or cracking is provided.

Thus, such a SiC film is initially used as a silicon raw material containing only a silicon raw material gas or a small amount of carbon raw material gas when flowing a silicon raw material gas and a carbon raw material gas onto a polysilicon substrate to deposit SiC. By flowing a gas to deposit a Si layer containing only Si or a small amount of SiC, and subsequently increasing the proportion of the carbon source gas to increase the deposition rate of SiC, and finally depositing only SiC by the method of the present invention. Formed easily and efficiently.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a member having a SiC coating of the present invention,
2 and 3 are graphs showing examples of changes in the SiC content ratio in the coating thickness direction of the member having the SiC coating of the present invention. 1 ... Polysilicon, 2 ... Coating.

Claims (2)

[Claims] 1. A member in which a coating film containing SiC and Si is formed on a polysilicon substrate, wherein the SiC content in the coating film is increased with increasing distance from the surface of the polysilicon substrate.
A member having a SiC coating, characterized in that the coating surface is composed of only SiC. 2. When depositing SiC by flowing a silicon source gas and a carbon source gas on a polysilicon base material, initially, a silicon source gas containing only a small amount of carbon source gas or a silicon source gas containing a small amount of carbon source gas is supplied. Only or a Si layer containing a small amount of SiC is deposited, and then the ratio of carbon source gas is sequentially increased.
A method for forming a SiC coating, characterized by increasing the rate of SiC deposition and depositing only SiC at the end.