Patent ID: 8765091

Claim:
A method for the manufacture of monolithic ingots of silicon carbide having a polytype of 4H and having a diameter of 50 to 150 mm comprising: i) introducing a mixture comprising polysilicon metal chips segregated by maximum dimension into sizes from 0.5 to 10 mm and carbon powder sifted into sizes from 5 to 125 um in an amount such that the molar ratio of polysilicon to carbon from 0.9 to 1.2 on a molar ratio basis into a first cylindrical reaction cell having a lid; ii) sealing the cylindrical reaction cell of i); iii) introducing the cylindrical reaction cell of ii) into a vacuum furnace; iv) evacuating the furnace of iii); v) filling the furnace of iv) with a gas mixture which is substantially inert gas to near atmospheric pressure; vi) heating the polysilicon metal chips and the carbon powder in the cylindrical reaction cell in the furnace of v) to a temperature of from 1600 to 2500° C.; vii) reducing the pressure in the furnace after vi) to less than 50 torr but not less than 0.05 torr; and viii) allowing for substantial sublimation and condensation of the vapors on the inside of the lid of the cylindrical reaction cell of vii).