Fundamnetal chemistry of silicon CVD

Model CVD reactor studies and UHV surface adsorption kinetic measurements are a powerful combination for investigation of the chemical mechanisms active in thermal silicon CVD from silane. We use the model reactor to separate two regimes of pressure and temperature in which SiH4 heterogeneous decomposition or homogeneous pyrolysis chemistry dominate the observed silicon film growth kinetics. Residence time of SiH4 in the reactor hot zone and total pressure are essential quantities distinguishing the two regimes. Growth rates are controlled by surface SiH4 adsorption kinetics in the heterogeneous regime. The regime we call the homogeneous regime is dominated by adsorption kinetics of higher silanes SinH2n+2. UHV adsorption kinetic measurements comparing SiH4, Si2H6, and Si3H8 chemisorption on clean, well defined single crystal surfaces are useful in understanding the two regimes. The UHV studies also demonstrate the necessity of considering the competitive adsorption of SiH4 with the higher silanes in film...