Patent ID: 7972942
Filing Date: 2011-07-05
Classification: H01L,Y10S

Abstract:
1. A method of reducing metal impurities of an upgraded metallurgical grade (UMG) silicon (Si) wafer by using an epitaxial silicon film, the method comprising: (a) obtaining a UMG Si substrate as a gettering material, wherein said UMG Si substrate has a purity not greater than 99.999% (5N) and a thickness not greater than 200 micrometers (μm); (b) placing said UMG Si substrate on a graphite susceptor into a reaction chamber of an atmospheric pressure chemical vapor deposition (APCVD) equipment and raising a temperature of said graphite susceptor in said reaction chamber of said APCVD equipment from a room temperature until at least 1100 Celsius degrees (° C.) by radiofrequency coils circled around said reaction chamber of said APCVD equipment; (c) obtaining a gas of dicholosilane (Si wherein, on raising said temperature in said reaction chamber to a temperature above 1100° C., some impurity in said UMG Si substrate is driven away from original sink positions, some impurity in said UMG Si substrate is dissolved, and both are released to new sink positions on said epitaxial Si thin film; wherein step (c) comprises steps of: wherein said UMG Si substrate obtains said relatively high temperature by directly contacting with said heated-up graphite susceptor; and wherein said epitaxial Si thin film obtains said relatively low temperature by directly perpendicularly facing said raw gas and said carrying gas; and (d) stopping providing said raw gas of Si