In‐situ doping of and trench‐refill with LPCVD‐poly‐silicon (I). (PH3/SiH4) ratio as a process‐controlling parameter

Abstract The ratio of phosphine‐ to silane concentration in the reaction gas mixture is a processcontrolling parameter in LPCVD‐polysilicon deposition not only with respect to doping level of the layer and layer growth rate on planar wafer surface, but also with respect to the degree of growth rate depression occurring by change‐over from wafer surface to sidewall area within trenches in the region of the upper rim of a trench. Trench refill behaviour deteriorates in consequence of growth rate depression within trench the more the higher the doping level of poly‐silicon will be chosen. Yet below a lower limit of doping poly‐silicon growth rate equals that of undoped poly‐silicon, and, as for trench‐refill, there is no difference in layer growth within trench and beyond.