POLYCRYSTALLINE SILICON CHARACTERISTICS DEPENDENCE ON STARTING AMORPHOUS MATERIAL

Silicon films, typically 1 mu m thick are deposited by low pressure chemical vapor deposition using pure silane at 550 degrees C and 3 deposition rates : 13, 23 and 45 Angstrom/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 degrees C is largely enhanced The crystallization time, defined from the in-situ conductivity measurements at 600 degrees C, is about 4 h for the high deposition rate amorphous film. Such time is very attractive in the attempt to obtain simultaneously << acceptable >> crystallization time and high quality polysilicon. This assertion is emphasized if we consider the total time t of the process (deposition time and crystallization time).