Patent ID: 7846252

Claim:
A method for producing a silicon wafer for an IGBT, comprising: by the Czochralski method, performing growth of a silicon ingot having an interstitial oxygen concentration [ 0 i] of not more than 7.0×10 17 atoms/cm 3 while controlling a ratio V/G of a growth rate V (mm/minute) of the silicon ingot and thermal gradient G (° C./mm) between the melting point and 1350° C. to be in a range of 0.22 to 0.27 during the growth of the silicon ingot; performing doping of phosphorus in the silicon ingot by performing neutron beam irradiation to the ingot such that concentration of phosphorus in the silicon ingot is not less than 4.3×10 13 atoms/cm 3 and not more than 2.2×10 14 atoms/cm 3 ; slicing a wafer from the ingot; performing annealing of the wafer in an oxidizing atmosphere containing at least oxygen at a temperature of T(° C.) that satisfies a formula, [ Oi]≦ 2.123×10 21 exp(−1.035/ k ( T+ 273)); and forming a polysilicon layer or a strained layer on one side of the wafer, wherein [ 0 i] is measured by Fourier transform infrared spectroscopy based on ASTM F-121(1979); and k is Boltzman constant (8.617×10 −5 (eV/K)).