JPH0697089A - Formation of sic film on face of carbonic base material - Google Patents

Abstract

PURPOSE:To provide a method for forming a uniform SiC film all over the face of a carbonic base material without a pin hole or a crack. CONSTITUTION:A disk-shaped carbonic base material having a through hole at the center thereof is hung by a supporting rod, and the carbonic base material is coated with an SiC film in a CVD method. An expansion graphite sheet 3 is provided at the supporting rod at least in a place where the carbonic base material becomes in contact with the inside face in the through hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a SiC film on a carbonaceous substrate surface, which is useful as a process operation for producing a high-purity SiC-coated carbonaceous member particularly applied to semiconductors.

[0002]

2. Description of the Related Art For example, a susceptor used for a semiconductor epitaxial growth is made of a disc-shaped carbonaceous substrate on which a SiC coating layer is formed.
The formation of the SiC coating on the surface of the carbonaceous substrate is usually carried out by directly pyrolyzing a halogenated organosilicon compound containing a carbon source such as a hydrocarbon in a reducing gas stream and directly on the surface of the carbonaceous substrate. It is carried out by a CVD method (Chemical Vapor Deposition method) in which SiC is vapor-deposited, but the formed SiC coating needs to be coated on the entire surface of the carbonaceous substrate as an extremely dense and homogeneous layer having no pinholes.

In the above-mentioned SiC coating operation, a carbonaceous substrate is placed in a heating vessel housed in a closed reaction tank via a plurality of support jigs (supporting members) having sharp tips. A method of feeding a reaction gas into the inside has been adopted. However,
In this method, the carbonaceous base material, which is brought into contact with the tip of the supporting jig serving as a supporting member, remains at a plurality of places without being covered with SiC, and the reaction gas does not evenly contact the upper and lower surfaces of the carbonaceous base material. Even if the reaction is interrupted midway and the contact point of the supporting jig is moved, the entire surface cannot be covered with a uniform SiC film.

Therefore, as a means for forming a uniform SiC coating layer while reducing the supporting contacts as much as possible, the through holes of the carbonaceous substrate are set in the reaction furnace in a suspended state on a rod-shaped supporting member. A way to do it has been devised. When the method is applied, the above-mentioned drawbacks are remarkably improved, but there is a problem that SiC is likely to be deposited at the contact point between the supporting rod and the through hole during the reaction and gradually laminated and fixed. If such a situation occurs, when the product coated with SiC is removed from the support rod, the coating locally peels off at the fixed portion, and remains as a minute pinhole or a minute chipped portion is generated. Invite.

By further developing the above suspension support method, the support contact of the carbonaceous substrate is moved through the reaction process by suspending the carbonaceous substrate on a rotating support rod having a cross-sectional area smaller than the diameter of the through hole. Film forming method (Japanese Patent Publication No. 63-13
No. 4663) has been proposed. However, this method complicates the structure of the device, so that the driving part does not move smoothly during long-term operation, or the carbonaceous substrate is partially damaged by mutual sliding with the through hole of the supporting rod. Si
There is a problem that pinholes and cracks occur after C coating.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted many studies on the improvement of the contact portion in order to solve the above problems, and as a result, a carbonaceous substrate to be covered with SiC and a supporting member. It has been confirmed that interposing a flexible expanded graphite sheet at the contacting portion with can effectively prevent coating defects such as pinholes and cracks not only in the suspension supporting method but also in any supporting means.

The present invention has been developed on the basis of the above-mentioned findings, and its purpose is to provide a carbonaceous substrate capable of forming a uniform coating layer on the entire surface without producing pinholes or cracks in the product. Another object of the present invention is to provide a SiC film forming method.

[0008]

In order to achieve the above object, a method for forming a SiC coating on a surface of a carbonaceous substrate according to the present invention is a CV covering a carbonaceous substrate with a supporting member over the entire surface.
In forming the SiC coating film by the D method, it is a structural feature that an expanded graphite sheet is interposed in a portion where the carbonaceous base material and the supporting member are in contact with each other.

A dense and highly pure isotropic graphite material is used as the carbonaceous substrate, and the shape is not particularly limited. These carbonaceous substrates are subjected to a CVD reaction in a state of being supported by a supporting member in a closed heating type reaction furnace. The support member is made of high-purity graphite or a ceramic material, and is designed to support a part of the carbonaceous substrate so as to expose almost the entire surface. For example, when the carbonaceous substrate has a disk shape with a through hole formed in the center, it serves as a support rod for suspending the through hole, and when the carbonaceous substrate has a flat plate shape, the upper and lower ends are locally fixed. It is formed into a jig structure that can be pulled or stopped.

It is an important requirement of the present invention to interpose an expanded graphite sheet in the portion where the above-mentioned support member and the carbonaceous substrate are in contact with each other. The expanded graphite sheet is an intercalation compound of natural graphite and sulfuric acid that is rapidly heated to swell graphite particles in the C-axis direction and roll-rolled to form a flexible sheet having good compression / restorability. For the purpose of the present invention, materials that have been subjected to high-purity treatment are effectively used. In particular, in the case of manufacturing a semiconductor epitaxial growth susceptor or the like that requires a high degree of purity, it is preferable to apply a thin SiC film formed beforehand by a CVD method on the surface of an expanded graphite sheet having an ash content of 20 ppm or less. .

The figure illustrates a state in which an expanded graphite sheet is interposed at a portion where the carbonaceous substrate and the supporting member are in contact with each other. Of these, Figure 1 (front view) and Figure 2 (side view)
1 shows a state in which a disk-shaped carbonaceous substrate 1 is suspended and supported by a supporting rod-shaped supporting member 2, and the expanded graphite sheet 3 is attached to a portion contacting the supporting member 2 and the inner surface of the through hole of the carbonaceous substrate. Is intervening. In this case, the expanded graphite sheet 3 is spread so as to cover the surface of the support member 2. 3 (front view) and FIG. 4 (side view) show a configuration in which the upper end and the lower end of a square plate-like carbonaceous substrate 1 are supported by a supporting member 2 of a fixing jig. The expanded graphite sheet 3 is interposed at the contact portion with the support member 2. Further, FIG. 5 (front view) and FIG. 6 (side view) show a mode in which a rectangular plate-like carbonaceous substrate 1 is leaned against and supported by a support member 2 which is a combination of a bottom bar and a vertical bar. The expanded graphite sheet 3 is interposed in the contacting portion. The support mechanism for the carbonaceous substrate is not limited to these illustrated structures.

To form a SiC film by the CVD method, a carbonaceous substrate is set in a heating reaction furnace in a supported state as described above, and a halogenated organosilicon compound such as CH ₃ SiCl ₃ is placed in the furnace. ₂ It is carried out by causing the reaction gas to flow into the carbonaceous substrate surface while being entrained in the gas while being brought into contact therewith.

[0013]

In the present invention, the expanded graphite sheet interposed between the abutting portions of the carbonaceous substrate and the supporting member has unique surface smoothness and self-lubricating property. It functions effectively to prevent the phenomenon of sticking in. In addition, since the expanded graphite sheet has flexibility of good compression / restoration in addition to the self-lubricating property, the carbonaceous material can be slid even when the support member is rotationally driven or moved in position. No surface damage. Furthermore, when SiC is fixed between the carbonaceous substrate and the expanded graphite sheet when forming a thick film, peeling and pinholes occur on the expanded graphite sheet side where the material strength is weak,
No defects occur on the carbonaceous substrate.

The synergistic effects of these functions effectively prevent the occurrence of pinholes, chips, cracks, etc. on the surface of the product after the SiC coating, and always provide a uniform SiC coating on the entire surface of the carbonaceous substrate. Can be formed. Furthermore,
When the expanded graphite sheet surface with an ash content of 20 ppm or less is coated with a SiC coating in advance, a sufficiently high purity is ensured in addition to the above-mentioned function, so the resulting SiC-coated carbonaceous product is also excellent. And purity characteristics are imparted.

[0015]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Example 1, Comparative Example A rod-shaped graphite support member partially covered with an expanded graphite sheet was provided inside a reaction furnace of a closed heating system having a reaction gas inlet and outlet. did. As shown in FIGS. 1 and 2, a carbonaceous substrate 1 having a disc shape with a diameter of 200 mm, a through hole diameter of 100 mm, and a thickness of 50 mm is formed on a portion of the support member 2 covered with the expanded graphite sheet 3 (compactness etc. (Suspended graphite material) so that the inner surface of the through-hole is in contact,
CH ₃ SiCl while maintaining the temperature in the furnace at 1450 ° C
By introducing a mixed reaction gas of ₃ and H ₂ , S by the CVD method
iC coating was performed. The CVD reaction was interrupted midway, the contact position between the expanded graphite sheet of the support member and the inner surface of the through hole of the carbonaceous substrate was changed, and the SiC coating operation was continued again. For comparison, a SiC coating was similarly formed on the surface of the carbonaceous substrate using a supporting member without an expanded graphite sheet (Comparative Example).

The SiC coated graphite material after the SiC coating treatment was removed and the state of the coated surface was investigated. Table 1 shows the results when the SiC coating was formed on 10 carbonaceous substrates.
It was shown to.

[0018]

[Table 1]

Example 2 A square plate-like carbonaceous substrate (high-purity isotropic graphite material) 1 is leaned against a supporting member 2 with an expanded graphite sheet 3 interposed at the contact portion as shown in FIGS. It was set in the reactor in this state. Other conditions are the same as in Example 1 and C
When the SiC coating was formed by VD, a uniform SiC coating was formed on the entire surface of the carbonaceous substrate, and no defect such as pinhole or chipping was observed on the coated surface including the intervening portion of the expanded graphite sheet. It was

Example 3 C under the same conditions as in Example 1 except that a SiC film was previously formed by the CVD method on the surface of the expanded graphite sheet having an ash content of 20 ppm or less which had been subjected to high-purity treatment and the coating was then interposed on the support rod.
A SiC film was formed on the carbonaceous substrate surface by the VD method. A uniform SiC coating is formed on the entire surface of the obtained product, and pinholes, peeling and chipping are dropped, including the inner surface of the through hole.
No abnormalities such as cracks were found. Also,
This SiC-coated graphite material was of extremely high purity and could be used as a susceptor for semiconductor epitaxial growth.

[0021]

As described above, according to the present invention, when the SiC coating film is formed on the carbonaceous substrate by the CVD method,
By interposing the expanded graphite sheet in the portion where the carbonaceous base material and the supporting member are in contact with each other, it is possible to always form a uniform SiC coating without pinholes, peeling and chipping. Therefore, it is extremely useful as a method for forming a SiC coating on the surface of a carbonaceous base material for various semiconductor device members such as a susceptor for epitaxial growth.

[Brief description of drawings]

FIG. 1 is a front view illustrating a supported state of a carbonaceous substrate.

2 is a side view of the supporting state according to FIG. 1. FIG.

FIG. 3 is a front view illustrating another support state of the carbonaceous substrate.

FIG. 4 is a side view of the supporting state according to FIG.

FIG. 5 is a front view illustrating another supporting state of the carbonaceous substrate.

6 is a side view of the supporting state according to FIG.

[Explanation of symbols]

 1 Carbonaceous Base Material 2 Support Member 3 Expanded Graphite Sheet

Claims (2)

[Claims] 1. When an SiC coating film is formed on the entire surface of a carbonaceous substrate by a CVD method while the carbonaceous substrate is supported by the supporting member, an expanded graphite sheet is interposed at a portion where the carbonaceous substrate and the supporting member are in contact with each other. On the surface of the carbon substrate characterized by
C film forming method. 2. The method for forming a SiC film on a carbon substrate surface according to claim 1, wherein an expanded graphite sheet having a SiC film formed by a CVD method on the surface of an expanded graphite sheet having an ash content of 20 ppm or less is used.