Apparatus for producing bulk silicon carbide

A sublimation furnace for forming silicon carbide 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 substantially solid silicon carbide precursor positioned in the lower region of the crucible;
• d) a seed module disposed in the upper region of the crucible, the seed module comprising:
• (1) a silicon carbide seed having a top surface and a bottom surface, the top surface exposed to the upper region of the crucible, the bottom surface facing the substantially solid silicon carbide precursor, wherein the bottom surface faces the lower region of the crucible, and
• (2) a seed holder having an upper section and a lower section that hold the silicon carbide seed therebetween, the upper section of the seed holder having a plurality of vapor release openings formed as holes around a center axis that is perpendicular to the bottom surface of the silicon carbide seed;
• and
• e) a vapor release ring disposed above the upper section of the seed holder, the vapor release ring formed with one or more holes therein being changeably aligned with one or more vent holes formed in the crucible.