A COMPARATIVE-STUDY OF O2 SIH4 AND N2O/SIH4 MIXTURES FOR SIO2 DEPOSITION IN A MICROWAVE AFTERGLOW/

Silicon dioxide films have been deposited in a microwave afterglow fro m N2O/SiH4 and O2/SiH4 mixtures. The effect of the pressure and of the substrate to silane injector &stance is investigated, and leads to co nclude that the growth mechanism is diffusion limited. In complement t o previous studies, the composition of films, obtained at several temp eratures and oxidant flow rates, is determined. The gas nature has a l ow influence on stoichiometry (O/Si approximately 2 whatever the condi tions are) but has an effect on the impurity content. Indeed, when N2O is used, nitrogen is incorporated but, at high temperature, the hydro gen content of the films is lower than for those made from O2. The imp urities are thought to come from uneasily desorbed byproducts.