Patent ID: 6713370
Filing Date: 2004-03-30
Classification: H01L

Abstract:
A process for heat-treating a single crystal silicon wafer to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step, the silicon wafer having a front surface, a back surface, a central plane between the front and back surfaces, a surface layer which comprises the region of the wafer between the front surface and a distance, D, measured from the front surface and toward the central plane, and a bulk layer which comprises the region of the wafer between the central plane and surface layer, the process comprising the steps of:heat-treating the wafer in an atmosphere to form crystal lattice vacancies in the surface and bulk layers of the wafer; thermally annealing the heat-treated wafer at a temperature in excess of about 1150Â° C. in an atmosphere having a partial pressure of oxygen of at least about 100 ppma; and, controlling the cooling rate of the annealed wafer to produce a wafer having a non-uniform distribution of crystal lattice vacancies with the concentration of vacancies in the bulk layer being greater than the concentration of vacancies in the surface layer, such that a thermal treatment of the wafer at a temperature in excess of 750Â° C. is capable of forming a denuded zone in the 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.