Patent ID: 6896728

Claim:
A process for heat-treating a Cz, single crystal silicon wafer, to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step, the 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 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 second region of the wafer between the central plane and the first region, wherein said wafer further comprises an axially symmetric region which has radial width of at least about three-tenths the length of the radius of the wafer and is substantially free of agglomerated intrinsic point defects the process comprising the steps of; subjecting the wafer to a heat-treatment to form crystal lattice vacancies in the front surface and bulk layers; and, controlling the cooling rate of the heat-treated wafer to produce a wafer having a vacancy concentration profile in which the peak density is at or near the central plane with the concentration generally decreasing in the direction of the front surface of the wafer and the difference in the concentration of vacancies in the front surface and bulk layers 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 zone with the concentration of the oxygen clusters or precipitates in the bulk layer being primarily dependant upon the concentration of vacancies.