Patent ID: 7344689

Claim:
A silicon wafer for an IGBT, which is sliced from a silicon ingot produced by the Czocralski method, the silicon wafer comprising: a concentration of interstitial oxygen [Oi] of not more than 7×10 17 atoms/cm 3 ; being doped with phosphorus; a polysilicon layer or a strained layer formed on one side of the silicon wafer; a density of COPs within the wafer of not more than 4.4×10 4 /cm 3 ; and a density of crystal defects of not more than 5×10 7 /cm 3 after being subjected to a double-step heat treatment including a heat treatment of the wafer for 4 hours at 800° C., and a heat treatment of the wafer for 16 hours at 1000° C.