Role of higher silanes in the plasma-induced deposition of amorphous silicon from silane

Time-resolved mass spectrometric data of the decay of monosilane concentration and of the formation and decay of disilane and trisilane are presented together with the silicon deposition rates measured under the same conditions. The data can be quantitatively explained by the mechanism involving, as a first step, the fragmentation of silane into SiH2 and H2, and deposition of a-Si via higher silanes which are formed by a fast insertion reaction of silene into gaseous silanes. Deposition via a SiH3 radical, which has been suggested by several groups, cannot explain the experimental data.