Patent ID: 7485928

Claim:
A wafer sliced from a single crystal silicon ingot grown by the Czochralski method comprising: a front surface, a back surface, an imaginary central plane between the front and back surfaces, a front surface layer which comprises a first region of a wafer between the front surface and a depth, D 1 , measured from the front surface and toward the central plane, and a bulk layer which comprises a second region of the wafer between the central plane and the first region; and the wafer has a resistivity of less than 5 mΩ-cm, is doped with phosphorous or arsenic, and has a supersaturated concentration of crystal lattice vacancies in the bulk layer whereby (a) oxygen precipitates form in the bulk layer at a concentration of at least 1×10 7 oxygen precipitates/cm 3 upon subjecting the wafer to an oxygen precipitation heat-treatment at a temperature in excess of 700° C., and (b) the supersaturated concentration of crystal lattice vacancies is reduced and a formation of oxygen precipitates in the bulk layer at a concentration of at least 1×10 7 oxygen precipitates/cm 3 is avoided by (i) heating the wafer to an annealing temperature of at least 950° C. at a rate of at least 2° C./sec, and (ii) cooling the wafer from the annealing temperature to 700° C. or less before the wafer is subjected to an oxygen precipitation heat-treatment at a temperature in excess of 700° C.