Patent ID: 7229693
Filing Date: 2007-06-12
Classification: C30B,H01L,Y10T

Abstract:
1. A single crystal silicon wafer comprising two major, generally parallel surfaces, one of which is a front surface of the wafer and the other of which is a back surface of the wafer, a central plane between the front and back surfaces, a circumferential edge joining the front and back surfaces, a central axis generally perpendicular to the front and back surfaces, a radius extending from the central axis to the circumferential edge, a front surface layer which comprises the region of the wafer between the front surface and a distance, D 1 , of at least about 10 micrometers measured from the front surface and toward the central plane, and a bulk layer which comprises a region of the wafer between the front surface layer and the central plane, the wafer being characterized in that: the wafer comprises an axially symmetric region in which vacancies are the predominant intrinsic point defect and which has no detectable agglomerated intrinsic point defects at a detection limit of 10 the wafer comprises a non-uniform concentration of vacancies with a maximum concentration located between the central plane and the front surface layer, the vacancy concentration generally increasing from the front surface to the region of maximum concentration and generally decreasing from the region of maximum concentration towards the central plane with the difference in the concentration of vacancies in the front surface layer and the bulk layer being such that a thermal treatment at a temperature in excess of 750° C., is capable of forming in the wafer a denuded zone in the front surface layer and oxygen clusters or precipitates in the bulk layer, with the concentration of the oxygen clusters or precipitates in the bulk layer being primarily dependant upon the concentration of vacancies.