Surface mechanisms in the UVCVD of SiO₂ films

Surface-sensitive multiple internal reflection absorption infrared spectroscopy has been applied to the study of the growth of SiO₂ films under far ultraviolet illumination. Spectra provide evidence for a previously unreported Si-H absorption peak occuring at 2208 cm^-1. It is shown that this line characterizes the molecular structure of the photochemisorption site of silane and that this phenomenon occurs on sites including hydroxyl groups which are also produced in a surface reaction. In the first step of silane photochemisorption, photoexcitation occurs on the surface while in the oxidization step, photoexcitation of oxygen molecules occurs in the gas phase, which completes the identification of a two-step surface mechanism for SiO₂ photodeposition. The existence of a transition of the growth front morphology from a rough pattern at room temperature to a smooth one at high temperature, within a common photochemical mechanism, may provide an experimental confirmation of recent theoretical models of kinetic growth.