Method for producing bulk silicon carbide by sublimation of a silicon carbide precursor prepared from silicon and carbon particles or particulate silicon carbide
A method of producing silicon carbide is disclosed. The method comprises the steps of providing a sublimation furnace comprising a furnace shell, at least one heating element positioned outside the furnace shell, and a hot zone positioned inside the furnace shell surrounded by insulation. The hot zone comprises a crucible with a silicon carbide precursor positioned in the lower region and a silicon carbide seed positioned in the upper region. The hot zone is heated to sublimate the silicon carbide precursor, forming silicon carbide on the bottom surface of the silicon carbide seed. Also disclosed is the sublimation furnace to produce the silicon carbide as well as the resulting silicon carbide material.
1. A method of forming silicon carbide comprising the steps of
i) providing a sublimation furnace comprising a furnace shell, at least one heating element positioned outside the furnace shell, and a hot zone positioned inside the furnace shell surrounded by insulation, the hot zone comprising
a) a crucible having an upper region and a lower region;
b) a crucible cover sealing the crucible;
c) a source module that is separable from a lower region of the crucible and prepared outside of the crucible, wherein the source module includes a substantially solid silicon carbide precursor mixture comprising silicon carbide that is contained within an outer annual chamber of the source module, wherein the substantially solid silicon carbide precursor mixture is porous and has a density that is less than a density of silicon carbide, further wherein the source module is a cylindrical insert that, when inserted in the lower region of the crucible, forms an inner annular chamber; and
d) a silicon carbide seed positioned in the upper region of the crucible, the silicon carbide seed having a top surface and a bottom surface, the bottom surface facing the substantially solid silicon carbide precursor mixture;
ii) after inserting the source module in the lower region of the crucible, heating the hot zone with the heating element to sublimate the substantially solid silicon carbide precursor mixture included in the source module;
iii) forming silicon carbide on the bottom surface of the silicon carbide seed; and
iv) removing the source module including the substantially solid silicon carbide precursor mixture.
2. The method of claim 1 , wherein the substantially solid silicon carbide precursor mixture is prepared by providing the source module and heating the source module to form the substantially solid silicon carbide precursor mixture.
3. The method of claim 1 , wherein the source module comprises a precursor chamber and wherein the substantially solid silicon carbide precursor mixture is contained within the precursor chamber.
4. The method of claim 1 , wherein the substantially solid silicon carbide precursor mixture has a molar ratio of carbon to silicon of greater than 1.0.
5. The method of claim 4 , wherein the molar ratio of carbon to silicon is from 1.05 to 1.5.
6. The method of claim 4 , wherein the molar ratio of carbon to silicon is from 1.1 to 1.3.
7. The method of claim 1 , wherein the silicon particles have an average particle size of from 0.1 mm to 10 mm.
8. The method of claim 7 , wherein the silicon particles have an average particle size of from 0.1 mm to 10 mm.
9. The method of claim 7 , wherein the silicon particles have an average particle size of from 1 mm to 4 mm.
10. The method of claim 1 , wherein the carbon particles have an average particle size of from 50 microns to 1000 microns.
11. The method of claim 7 , wherein the carbon particles have an average particle size of from 50 microns to 1000 microns.
12. The method of claim 10 , wherein the carbon particles have an average particle size of from 85 microns to 500 microns.
13. The method of claim 1 , wherein the substantially solid silicon carbide precursor mixture is a heterogeneous mixture of silicon particles and carbon particles.
14. The method of claim 13 , wherein the substantially solid silicon carbide precursor mixture comprises alternating layers of silicon particles and carbon particles.
15. A method of forming silicon carbide comprising the steps of
i) providing a sublimation furnace comprising a furnace shell, at least one heating element positioned outside the furnace shell, and a hot zone positioned inside the furnace shell surrounded by insulation, the hot zone comprising
a) a crucible having an upper region and a lower region;
b) a crucible cover sealing the crucible;
c) a source module that is separable from a lower region of the crucible and prepared outside of the crucible, wherein the source module includes a substantially solid silicon carbide precursor mixture comprising silicon carbide that is contained within an outer annual chamber of the source module, wherein the substantially solid silicon carbide precursor mixture is porous and has a density that is less than a density of silicon carbide, further wherein the source module is a cylindrical insert that, when inserted in the lower region of the crucible, forms an inner annular chamber; and
d) a silicon carbide seed positioned in the upper region of the crucible, the silicon carbide seed having a top surface and a bottom surface, the bottom surface facing the substantially solid silicon carbide precursor mixture;
ii) after inserting the source module in the lower region of the crucible, heating the hot zone with the heating element to sublimate the substantially solid silicon carbide precursor mixture included in the source module; and
iii) forming silicon carbide on the bottom surface of the silicon carbide seed; and
iv) removing the source module including the substantially solid silicon carbide precursor mixture.
16. A method of forming silicon carbide comprising the steps of
i) preparing a source module that is separable from a lower region of a crucible and prepared outside of the crucible, wherein the source module includes a substantially solid silicon carbide precursor mixture comprising silicon carbide that is contained within an outer annual chamber of the source module, wherein the substantially solid silicon carbide precursor mixture is porous and has a density that is less than a density of silicon carbide, further wherein the source module is a cylindrical insert that when inserted in the lower region of the crucible, forms an inner annular chamber;
ii) after preparing the source module, providing a sublimation furnace comprising a furnace shell, at least one heating element positioned outside the furnace shell, and a hot zone positioned inside the furnace shell surrounded by insulation, the hot zone comprising:
a) the crucible having an upper region and the lower region,
b) a crucible cover sealing the crucible, and
c) a silicon carbide seed positioned in the upper region of the crucible, the silicon carbide seed having a top surface and a bottom surface, the bottom surface facing the substantially solid silicon carbide precursor mixture;
iii) after inserting the source module in the lower region of the crucible, heating the hot zone with the heating element to sublimate the substantially solid silicon carbide precursor mixture included in the source module;
iv) forming silicon carbide on the bottom surface of the silicon carbide seed; and
v) removing the source module including the substantially solid silicon carbide precursor mixture.