High quality unhydrogenated low-pressure chemical vapor deposited polycrystalline silicon

Intrinsic amorphous silicon (a-Si) is deposited at 550°C and at different pressures using low-pressure chemical vapor deposition (LPCVD) technique. These deposition pressures (90, 150 and 200 Pa) were obtained by pushing back the powder regime formation that occurred around 90 Pa. Using kinetics of solid phase crystallization monitored by in situ measurements of the film conductance, optical transmission, dark conductivity vs temperature, Hall effect, and photoconductivity under monochromatic light were measured to determine the properties of crystallized films; we show that device quality is obtained at larger deposition pressure above which the powder formation regime begins. Particularly, the largest Hall mobility known to us of undoped polycrystalline silicon (polysilicon) (40 cm2/V s) is reported. Moreover at this larger deposition pressure, a deposition rate of 0.8 μm/h is obtained. This rate is the largest obtained by LPCVD of a-Si to our knowledge. The improvements of some electrical properties of the polycrystalline films are explained in terms of a high pressure relaxed a-Si network.