Hot-Wire Chemical Vapor Deposition of Silicon from Silane: Effect of Process Conditions

We have examined the deposition of uniform polycrystalline silicon films over large surface areas for application in photovoltaics and flat panel displays. Depositions were conducted using a commercially available hot-wire chemical vapor deposition chamber. We investigated the effect of the silane flow rate (4−60 sccm), filament temperature (1550−1850 °C), total pressure (25−1000 mTorr), substrate temperature (400−600 °C), and hydrogen dilution on the exit gas-phase composition, film growth rate, and film crystalline fraction. Experiments show that the growth rate increases with silane flow rate and is independent of the substrate temperature. The growth rate variation with pressure and filament temperature is observed to change with the axial position of the substrate. A transition from amorphous (a-Si) to polycrystalline (poly-Si) silicon films is observed with increasing total pressure, filament temperature, and substrate temperature and with decreasing silane flow rate. The effect of hydrogen dilution is found to be equivalent to the effect of increasing gas pressure using pure silane. The experiments suggest that the interaction of atomic hydrogen with the growing surface leads to the growth of the crystalline phase in the silicon films.