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 R F glow discharge decomposition of pure silane and mixtures of silane w ith H-2 or He has been studied using UV-visible and infrared ellipsome try. The substrate as well as the gas phase conditions strongly influe nce the early stages of a-Si:H growth. As compared to pure silane cond itions, when using H-2 or He dilution of silane, thicker films must be deposited for SIH bonding to become dominant with respect to SiH2. Mo reover, in the case of high deposition rates from silane-helium mixtur es, the SiH2 band increases with film thickness, indicating that, cont rary to low deposition rate conditions, SiH2 is present in the bulk of the film.