ON CHEMICAL-KINETICS OF SILICON DEPOSITION FROM SILANE (IV) - INSITU PHOSPHORUS DOPING OF LPCVD POLY SILICON IN THE TEMPERATURE-RANGE 900-950 K

Highly in-situ phosphorus-doped LPCVD poly silicon deposition from mixtures consisting of silance and phosphine has been investigated for limited conditions regarding temperature, silane input, phosphine-silane ratio and total pressure. Agreeing with the deposition of undoped poly silicon, growth rate linearly decays along the axis of the wafer cage applied for in-situ doped poly silicon. In consequence layer growth should be controlled by a chemical reaction of 0.5th order. In contrast to undoped poly silicon the slope of axial growth rate decay increases with the distance between wafers increased. This behaviour is a proof for a homogneous chemical reaction mechanism. The silicon forming reaction is characterized by an activation energy of about 25 kcal/mole for PH3/SiH4 = 0.003.