IN-SITU UV-VISIBLE AND INFRARED ELLIPSOMETRY STUDY OF THE INFLUENCE OF SILANE DILUTION ON THE GROWTH OF HYDROGENATED AMORPHOUS-SILICON

The initial stages of hydrogenated amorphous silicon growth from the RF glow discharge decomposition of pure silane and mixtures of silane with H-2 or He has been studied using UV-visible and infrared ellipsometry. The substrate as well as the gas phase conditions strongly influence the early stages of a-Si:H growth. As compared to pure silane conditions, when using H-2 or He dilution of silane, thicker films must be deposited for SIH bonding to become dominant with respect to SiH2. Moreover, in the case of high deposition rates from silane-helium mixtures, the SiH2 band increases with film thickness, indicating that, contrary to low deposition rate conditions, SiH2 is present in the bulk of the film.