High quality unhydrogenated low-pressure chemical vapor deposited polycrystalline silicon

Intrinsic amorphous silicon (a-Si) is deposited at 550 degrees C and at dif ferent pressures using low-pressure chemical vapor deposition (LPCVD) techn ique. These deposition pressures (90, 150 and 200 Pa) were obtained by push ing back the powder regime formation that occurred around 90 Pa. Using kine tics of solid phase crystallization monitored by in situ measurements of th e 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 qua lity is obtained at larger deposition pressure above which the powder forma tion regime begins. Particularly, the largest Hall mobility known to us of undoped polycrystalline silicon (polysilicon) (40 cm(2)/N s) is reported. M oreover at this larger deposition pressure, a deposition rate of 0.8 mu m/h is obtained. This rate is the largest obtained by LPCVD of a-Si to our kno wledge. The improvements of some electrical properties of the polycrystalli ne films are explained in terms of a high pressure relaxed a-Si network. (C ) 2000 Elsevier Science B.V. All rights reserved.