Chemistry of inorganic compounds – Silicon or compound thereof – Binary compound
Reexamination Certificate
1999-02-03
2001-04-17
Utech, Benjamin L. (Department: 1765)
Chemistry of inorganic compounds
Silicon or compound thereof
Binary compound
C117S004000, C117S007000, C117S009000, C117S084000, C117S088000, C117S951000
Reexamination Certificate
active
06217842
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application discloses subject matter in common with pending application Ser. No. 09/147,456, filed Dec. 29, 1998.
TECHNICAL FIELD
The present invention relates to single crystal SiC and a method of producing the same, and more particularly to single crystal SiC which is used as a substrate wafer for a high temperature semiconductor electronic element such as a light-emitting diode, a ULSI (Ultra Large-Scale Integrated circuit), a rectifying element, a switching element, an amplifying element, and an optical sensor, and also to a method of producing the same.
BACKGROUND ART
SiC (silicon carbide) is superior in heat resistance and mechanical strength than existing semiconductor materials such as Si (silicon) and GaAs (gallium arsenide), and also in its high-temperature property, high-frequency property, dielectric property, and resistance to environments. In addition, it is easy to perform valence control of electrons and holes by doping an impurity. Moreover, SiC has a wide band gap (for example, single crystal 6H-SiC has a band gap of about 3.0 eV, and single crystal 4H-SiC has a band gap of 3.26 eV). For these reasons, SiC receives attention and is expected as a semiconductor material for a next-generation power device.
As a method of growing (producing) single crystal SiC of this type, known are a method in which single crystal SiC is grown by a sublimation and recrystallization method using a seed crystal, and that in which, in the case of a high temperature, epitaxial growth is conducted on a silicon substrate by using a chemical vapor deposition method (CVD method), thereby growing single crystal cubic SiC (&bgr;-SiC).
In the above-described conventional production methods, however, the crystal growth rate is as low as 1 &mgr;m/hr. Furthermore, the sublimation and recrystallization method has a problem in that pin holes which have a diameter of several microns and which pass through the crystal in the growing direction remain at about 100 to 1,000/cm
2
in a growing crystal. Such pin holes are called micropipe defects and cause a leakage current when a semiconductor device is fabricated. These problems block a practical use of single crystal SiC which has superior characteristics as compared with other existing semiconductor materials such as Si and GaAs as described above.
In the case of the high-temperature CVD method, the substrate temperature is as high as 1,700 to 1,900° C., and it is required to produce a high-purity reducing atmosphere. Therefore, the method has a problem in that it is difficult to conduct the method from the view point of installation. Furthermore, the method has another problem in that, because of epitaxial growth, the growth rate is naturally limited.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide single crystal SiC of high quality which is little affected by lattice defects and micropipe defects, and a method of producing single crystal SiC which can produce such single crystal SiC easily and efficiently from the point of view of installation and workability, and which can expedite the practical use of the single crystal as a semiconductor material.
The single crystal SiC of the present invention is characterized in that a complex in which a polycrystalline plate consisting of Si and C atoms and having a thickness of 10 &mgr;m or more is stacked on the surface of a single crystal SiC base material and is subjected to a heat treatment, whereby polycrystals of the polycrystalline plate are transformed into a single crystal.
According to the thus configured present invention, polycrystals of the polycrystalline plate are phase-transformed by only applying means which thermally processes a complex consisting of a single crystal SiC base material and a polycrystalline plate stacked on the surface of the base material, and which is simple from the point of view of installation and workability, so that a single crystal which is oriented in the same direction as the crystal axis of the single crystal SiC base material is efficiently grown. Furthermore, the thickness of the polycrystalline plate of the complex is set to be 10 &mgr;m or more. Even when micropipe defects which impede transformation of polycrystals of the polycrystalline plate into a single crystal exist in the vicinity of the surface of the single crystal SiC base material, therefore, a single crystal can be grown to a large size in a range where the single crystal is not affected by the defects. Consequently, it is possible to obtain single crystal SiC of high quality which is substantially free from micropipe defects and defects affected by the micropipe defects. As a result, it is possible to attain the effect of expediting the practical use of single crystal SiC which is superior in its high-temperature property, high-frequency property, dielectric property, and a high resistance to environments to existing semiconductor materials such as Si (silicon) and GaAs (gallium arsenide), and which is expected as a semiconductor material for a power device.
The method of producing single crystal SiC of the present invention is characterized in that a polycrystalline plate consisting of Si and C atoms and having a thickness of 10 &mgr;m or more is stacked on the surface of a single crystal SiC base material, the complex is then subjected to a heat treatment to transform polycrystals of the polycrystalline plate into a single crystal and grow the single crystal.
Also the thus configured production method can attain the effect that single crystal SiC of high quality which is substantially free from micropipe defects and defects affected by the micropipe defects is grown easily and efficiently so that single crystal SiC which is available as a semiconductor material having a very high performance can be stably produced and supplied on an industrial scale.
In the single crystal SiC and the method of producing single crystal SiC of the present invention, when the polycrystalline plate constituting the complex is a polycrystalline &bgr;-SiC plate grown on the surface of a single crystal SiC base material by physical vapor deposition or thermochemical vapor deposition and the thermochemical vapor deposition temperature of the polycrystalline &bgr;-SiC plate is set to be in the range of 1,300 to 1,600° C., the present invention attains an effect that single crystal SiC of high purity and high quality and having lattice defects and micropipe defects which are smaller in number than those of the single crystal SiC base material can be obtained, while suppressing the entering of impurities between the single crystal SiC base material and the polycrystalline plate on the surface thereof, and diffusion of the impurities.
REFERENCES:
patent: 4590130 (1986-05-01), Cline
Champagne Donald L.
Jones Tullar & Cooper P.C.
Nippon Pillar Packing Co. Ltd.
Utech Benjamin L.
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