Time-resolved cavity ringdown study of the Si and SiH3 surface reaction probability during plasma deposition of a-Si:H at different substrate temperatures

Time-resolved cavity ringdown spectroscopy (-CRDS) has been applied to determine the surface reaction probability of Si and SiH3 radicals during plasma deposition of hydrogenated amorphous silicon (a-Si:H). In an innovative approach, our remote Ar-H2-SiH4 plasma is modulated by applying pulsed rf power to the substrate and the resulting time-dependent radical densities are monitored to yield the radical loss rates. It is demonstrated that the loss rates obtained with this -CRDS technique equal the loss rates in the undisturbed plasma and the determination of the gas phase reaction rates of Si and SiH3 as well as their surface reaction probability is discussed in detail. It is shown that Si is mainly lost in the gas phase to SiH4 [reaction rate kr = (3.0±0.6)×10–16 m3s–1], while the probability for Si to react at an a-Si:H surface is 0.95