EVOLUTION OF MICROSTRUCTURES IN HYDROGENATED SILICON FILMS PREPARED BY DILUTED-HYDROGEN AND HYDROGEN-ATOM-TREATMENT METHODS

Nuclear magnetic resonance (NMR), Fourier transform infrared spectrosc opy, and Raman studies on microstructures of hydrogenated silicon film s that were fabricated by diluted-hydrogen and hydrogen-atom-treatment methods are presented. The diluted-hydrogen samples tend to show a ve ry sharp line shape in the NMR spectra at substrate temperatures highe r than 300-degrees-C, and the addition of atomic hydrogen treatment ca n produce the same NMR spectra at a lower temperature of about 250-deg rees-C. The Raman scattering spectra show that the atomic hydrogen tre atment creates the microcrystalline phase while the diluted-hydrogen m ethod produces amorphous phase plus a small quantity of microcrystalli ne phase. The infrared-absorption spectra also indicate an increase of SiH2 bonding configuration and a hydrogen content reduction when atom ic hydrogen treatment is employed. The relation between the origin of the sharp line shape in the NMR spectra and the formation of the micro crystalline phase is also discussed. Together with increase of dark co nductivity and reduction of the photo-to-dark conductivity ratio, thes e samples indicate that with appropriate hydrogen incorporation during deposition, and with plasma hydrogen treatment, these films should po ssess a much more compact structure. These results suggest that the de gree of crystallinity of hydrogenated silicon films can be systematica lly adjusted. A qualitative model based on our experimental data is pr esented to illustrate the formation procedures of microcrystalline-pha se hydrogenated silicon under the influence of plasma hydrogen and hyd rogen dilution.