Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2001-08-27
2003-05-20
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S781000
Reexamination Certificate
active
06566279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for fabricating a SiC film and a SiC multi-layered film structure, particularly usable for various environment-resistance device and various semiconductor device.
2. Description of the Prior Art
SiC material has a larger bandgap, a larger electric field for dielectric breakdown, a larger saturated drift velocity and a larger thermal conductivity than Si material, so that it can be expected to be used for an environment-resistance device under a high temperature atmosphere and a large radiation atmosphere, in which a given device made of Si material or GaAs material can not be employed, and for a high frequency- or a high power-semiconductor device.
Moreover, the SiC material can be also expected for a substrate for GaN devices such as a microwave device and a blue-violet laser. That is why a given electrode can be easily formed on the back surface of the substrate because the SiC material has a relatively large electric conductivity and the substrate made of the SiC material has a large thermal emission capacity due to the large thermal conductivity. Furthermore, a given resonance mirror can be easily fabricated through the cleave of the SiC material and the SiC material has its lattice constant almost equal to a GaN-based semiconductor material (the difference in lattice constant between the SiC material and the GaN based material is about 3%).
Conventionally, a SiC substrate was made by a sublimation method or a hetero-epitaxy method for a Si substrate. However, the SiC substrate made by the sublimation method was likely to have much throughout hole defects called as micropipes. Moreover, the sublimation method has difficulty in fabricating a large sized SiC substrate.
On the other hand, the hetero-epitaxy method can make a large sized SiC film on a Si wafer at low cost, and thus, can make a large sized SiC substrate. However, the difference between the SiC film and the Si wafer comes up to about 20%, so that it is required that a SiC underfilm having much clystallographical information of the Si wafer is formed, heading to forming the SiC film.
The SiC underfilm is made by a so-called carbonization method. In this case, the Si substrate (Si wafer) is heated to about 900° C. or over, with supplying hydrocarbon gas having only carbon source onto the Si substrate. Just then, the Si elements of the Si substrate and the carbon elements of the hydrocarbon gas are reacted on the surface of the Si substrate, and thus, a thin underfilm made of a SiC single crystal is fabricated on the Si substrate.
However, the carbonization method may make much hollow voids in the Si substrate and deteriorate the flatness of the interface between the SiC underfilm and the Si substrate due to the outdiffusion of the Si elements. Therefore, the crystallinity of the SiC underfilm is deteriorated and as a result, the flatness of the SiC underfilm is deteriorated. Accordingly, the crystallinity and the flatness of the SiC film to be fabricated on the SiC underfilm are deteriorated, so that a SiC substrate having favorable physical properties can not be provided.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for fabricating a SiC film with good crystallity and flatness without the step of thermally treating at a high temperature, and to provide a method for fabricating a SiC multilayered film structure including the step of forming a SiC underfilm with the above fabricating method of a SiC film.
For achieving the above object, this invention relates to a method for fabricating a SiC film comprising the steps of:
preparing a Si-contained base material and
supplying an organic silicon gas having Si—H bond and Si—C bond onto a main surface of the Si-contained base material, thereby to form a SiC film on the main surface.
The inventors have intensely studied to obtain a new fabricating method for a SiC film without the thermal treatment at a high temperature. Then, they have developed various fabricating methods and varied the fabricating conditions in each of the fabricating methods. As a result, they have found out that the use of an organic silicon gas having Si—H bond and Si—C bond, as a substitute for the conventional hydrocarbon gas, can make a SiC film with good crystallinity and flatness without the step of thermally treating the base material at a high temperature on which the SiC film is formed.
According to the present invention, it is not required that the base material containing Si element is heated to a high temperature of 900° C. or over. Therefore, the deterioration of the flatness and the crystallinity of the SiC film due to the hollow voids and outdiffusion of the Si element in the base material can be repressed, so that a SiC film with excellent crystallinity and flatness can be provided.
In the present invention, the thermal treatment for the base material is not always excluded. Preferably, the base material is heated to a temperature of 800° C. and below, particularly to a temperature within 450-650° C. In this case, the flatness of the thus obtained SiC film can be developed with maintaining the high crystallinity.
The fabricating method of the present invention can be preferably applied for a SiC multi-layered film structure such as a SiC substrate. That is, the above SiC film is formed as a SiC underfilm on a main surface of a Si-contained base material, and the fabricating method of the present invention is characterized in that an organic silicon gas having Si—H bond and Si—C bond is supplied onto the main surface of the base material and thus, the SiC underfilm is fabricated on the main surface.
According to the fabricating method of a SiC multi-layered film structure of the present invention, the crystallinity and the flatness of the SiC underfilm can be developed and thus, those of a SiC film to be formed on the SiC underfilm can be also developed.
As a result, a SiC substrate having good crystallinity and flatness can be provided.
REFERENCES:
patent: 5313078 (1994-05-01), Fujii et al.
patent: 5677236 (1997-10-01), Saitoh et al.
Nakazawa Hideki
Suemitsu Maki
Fourson George
Lee Hsien-Ming
Oliff & Berridg,e PLC
Tohoku University
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