Sublimation of silicon carbide to produce large, device quality single crystals of silicon carbide
First Claim
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1. A method of reproducibly controlling the growth of large single crystals of the use of impurities as a primary mechanism for controlling polytype growth, and which crystals are suitable for use in producing electrical devices, the method comprising:
- introducing a monocrystalline seed crystal of silicon carbide of desired polytype and a silicon carbide source powder into a sublimation system;
raising the temperature of the silicon carbide source powder to a temperature sufficient for the source powder to sublime;
whileelevating the temperature of the growth surface of the seed crystal to a temperature approaching the temperature of the source powder, but lower than the temperature of the source powder and lower than that at which silicon carbide will sublime under the gas pressure conditions of the sublimation system; and
generating and maintaining a substantially constant flow of vaporized Si, Si2 C, and SiC2 per unit area per unit time from the source powder to the growth surface of the seed crystal for a time sufficient to produce a desired amount of macroscopic growth of monocrystalline silicon carbide of desired polytype upon the seed crystal.
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Abstract
The present invention is a method of forming large device quality single crystals of silicon carbide. The sublimation process is enhanced by maintaining a constant polytype composition in the source materials, selected size distribution in the source materials, by specific preparation of the growth surface and seed crystals, and by controlling the thermal gradient between the source materials and the seed crystal.
635 Citations
29 Claims
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1. A method of reproducibly controlling the growth of large single crystals of the use of impurities as a primary mechanism for controlling polytype growth, and which crystals are suitable for use in producing electrical devices, the method comprising:
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introducing a monocrystalline seed crystal of silicon carbide of desired polytype and a silicon carbide source powder into a sublimation system; raising the temperature of the silicon carbide source powder to a temperature sufficient for the source powder to sublime;
whileelevating the temperature of the growth surface of the seed crystal to a temperature approaching the temperature of the source powder, but lower than the temperature of the source powder and lower than that at which silicon carbide will sublime under the gas pressure conditions of the sublimation system; and generating and maintaining a substantially constant flow of vaporized Si, Si2 C, and SiC2 per unit area per unit time from the source powder to the growth surface of the seed crystal for a time sufficient to produce a desired amount of macroscopic growth of monocrystalline silicon carbide of desired polytype upon the seed crystal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 29)
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28. A method of reproducibly controlling the growth of large single crystals of a single polytype of silicon carbide independent of the use of impurities as a primary mechanism for controlling polytype growth, and which crystals are suitable for use in producing electical devices, the method comprising:
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introducing a monocrystalline seed crystal of silicon carbide of desired polytype and a silicon carbide source powder into a sublimation system, with the source powder having a selected composition of polytypes, a selected predetermined distribution of surface areas, and a selected predetermined distribution of particle sizes; raising the temperature of the silicon carbide source powder to a temperature sufficient for the source powder to sublime;
whileelevating the temperature of the growth surface of the seed crystal to a temperature approaching the temperature of the source powder, but lower than the temperature of the source powder and lower than that at which silicon carbide will sublime under the gas pressure conditions of the sublimation system; and maintaining the selected composition of polytypes in the source powder substantially constant throughout the growth process;
whilemaintaining the selected distribution of surface areas in the source powder substantially constant throughout the growth process; and
whilemaintaining the selected distribution of particle sizes in the source powder substantially constant throughout the growth process, to thereby generate and maintain a substantially constant flow of vaporized Si, Si2 C, and SiC2 per unit area per unit time from the source powder to the growth surface of the seed crystal, and all for a time sufficient to produce a desired amount of macroscopic growth of monocrystalline silicon carbide of desired polytype upon the seed crystal. .Iadd.
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Specification