Polycrystalline Silicon Characteristics Dependence on Starting Amorphous Material

Silicon films, typically 1 µm thick, are deposited by low pressure chemical vapor deposition using pure silane at 550°C and 3 deposition rates : 13, 23 and 45 Å/mn. Using numerous physical, optical and electrical characterization techniques, we show an evident amorphous character of these as-deposited films. Films deposited at high rate correspond more likely to the relaxed amorphous network. The quality of the polysilicon produced by annealing these high deposition rate films at 600°C is largely enhanced. The crystallization time, defined from the in-situ conductivity measurements at 600°C, is about 4 h for the high deposition rate amorphous film. Such time is very attractive in the attempt to obtain simuitaneously «acceptable» crystallization time and high quality polysilicon. This assertion is emphasized if we consider the total the t of the process (deposition time and crystallization time)