Carbon in Epitaxial Silicon

Abstract

Epitaxial Si layers have been doped with carbon from a silicon tetrachloridemethane system, and the carbon content has been chemically analyzed. The levels of carbon content range from (undoped) through (moderate doping), to a saturation content which induces complete conversion to . Influence of the carbon content on the crystalline perfection of the Si layers is found to be negligible up to concentrations of 1018 atoms C/cm3; at concentrations near 1019 atoms C/cm3 many polycrystalline inclusions are formed. Spreading resistance measurements which reveal doping profiles show significant increases in resistance only in layers which can show some change of phase. Direct evidence is presented demonstrating that the retention of carbon in the deposited layers is both by diffusion induced substitution and by chemical reaction. The retention of excess carbon interstitially is inferred.