Crystallization of n-doped amorphous silicon PECVD films: comparison between SPC and RTA methods

Amorphous silicon films are deposited by radio-frequency plasma-enhanced ch emical-vapor deposition (RF-PECVD) with different n-doping rates. The amorp hous films are subsequently crystallized using either solid phase crystalli zation (SPC) or rapid thermal annealing (RTA). We compare the effect of the n-doping rate on some properties of the microcrystalline silicon films obt ained with both techniques. In the SPC process, the time required for the b eginning of the crystallization decreases with increasing phosphorus doping . Moreover, doped films present slightly higher crystal size than intrinsic films but the doping rate does not significantly influence the grain size. For RTA, the doping rate decreases the crystallization temperature and inc reases significantly the crystal size. Whatever the doping rate, the averag e grain sizes obtained by RTA are larger than those obtained by SPC. The el ectrical resistance of the crystallized films also depends on the crystalli zation process: RTA films present a lower dark conductivity than SPC films. These results are discussed taking into account the different kinetics of both crystallization techniques and the role played by the silicon dangling bonds and their charge states on the crystal growth. (C) 2000 Elsevier Sci ence B.V. All rights reserved.