Patent ID: 9129919
Filing Date: 2015-09-08
Classification: C30B,H01L

Abstract:
1. A process for heat-treating a single crystal silicon wafer sliced from a single crystal silicon ingot grown by the Czochralski method 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 front surface layer which comprises the region of the wafer extending in the axial direction from the front surface toward the central plane to a distance, D, from the front surface, and a bulk layer which comprises the region of the wafer between the central plane and front surface layer, the process comprising: subjecting the wafer to a heat-treatment to install in the wafer a concentration of oxygen precipitate nuclei comprising crystal lattice vacancies in the front surface and bulk layers of the wafer, wherein at least a portion of the oxygen precipitate nuclei are inactive oxygen precipitate nuclei and a portion are active oxygen precipitate nuclei, the oxygen precipitate nuclei being characterized such that upon being subjected to an NEC1 oxygen precipitation heat treatment active oxygen precipitate nuclei are converted to oxygen precipitates and inactive oxygen precipitate nuclei do not form oxygen precipitates; controlling the cooling rate of the heat-treated wafer to produce a wafer having a concentration profile of oxygen precipitate nuclei wherein the maximum concentration is in the bulk region with the concentration generally decreasing in the direction of the front surface of the wafer and the difference in the concentration of oxygen precipitate nuclei in the front surface and bulk layers being such that, if the wafer is subjected to a subsequent oxygen precipitation heat treatment, an oxygen precipitate-free denuded zone is formed in the front surface layer and oxygen precipitates are formed in the bulk layer with the concentration of the oxygen precipitates in the bulk layer being primarily dependent upon the oxygen precipitate nuclei; and subjecting the wafer to a heat treatment at a temperature of at least about 400° C. and no greater than about 600° C. for at least about 1 hour to activate at least a portion of the inactive oxygen precipitate nuclei in the wafer.