Method and apparatus for producing bulk silicon carbide using a silicon carbide seed
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:
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; and
c) a silicon carbide precursor positioned in the lower region of the crucible;
ii) preparing, outside of the crucible, a seed module with a seed holder holding a silicon carbide seed therein, wherein the seed holder includes a plurality of vapor release openings positioned around a center axis of the seed holder;
iii) disposing the silicon carbide seed within the seed module between an upper section and a lower section of the seed holder while the seed module is outside of the crucible, wherein the silicon carbide seed includes a top surface and a bottom surface, and wherein the plurality of vapor release openings are formed in the upper section of the seed holder below the bottom surface of silicon carbide seed;
iv) after disposing the silicon carbide seed within the seed module while the seed module is outside of the crucible, disposing the seed module containing the silicon carbide seed therein in the upper region of the crucible;
v) heating the hot zone with the at least one heating element to sublimate the silicon carbide precursor; and
vi) forming the silicon carbide on the bottom surface of the silicon carbide seed while the top surface of the silicon carbide seed is exposed.
2. The method of claim 1 , wherein the plurality of vapor release openings are positioned symmetrically around the center axis.
3. The method of claim 1 , wherein the silicon carbide seed is a circular silicon carbide wafer, and wherein the plurality of vapor release openings are equidistant from the center axis.
4. The method of claim 1 , wherein the top surface of the silicon carbide seed comprises a seed protection layer.
5. The method of claim 4 , wherein the seed protection layer has a thickness of less than 250 microns.
6. The method of claim 4 , wherein the seed protection layer has a thickness of less than 100 microns.
7. The method of claim 6 , wherein the thickness of the seed protection layer is 10 microns to 90 microns.
8. The method of claim 6 , wherein the thickness of the seed protection layer is 30 microns to 80 microns.
9. The method of claim 6 , wherein the thickness of the seed protection layer is 50 microns to 70 microns.
10. The method of claim 4 , wherein the seed protection layer comprises at least two coating layers.
11. The method of claim 10 , wherein at least one coating layer is a cured photoresist layer.
12. The method of claim 11 , wherein the cured photoresist layer has a thickness of 2 microns to 5 microns.
13. The method of claim 10 , wherein at least one coating layer is a graphite coating layer.
14. The method of claim 4 , wherein the silicon carbide seed has a silicon face and a carbon face, and wherein the top surface is the silicon face.
15. The method of claim 1 , further comprising:
preparing a source module outside of the crucible;
disposing the silicon carbide precursor within the source module while the source module is outside of the crucible; and
after disposing the silicon carbide precursor within the source module while the source module is outside of the crucible, disposing the source module containing the silicon carbide precursor therein inside of the crucible.
16. The method of claim 1 , further comprising:
disposing a vapor release ring with one or more holes formed therein above the upper section of the seed holder, the one or more holes configured to be aligned with one or more vent holes formed in the crucible.