OPTICAL AND MECHANICAL CHARACTERIZATION OF EVAPORATED SIO2 LAYERS - LONG-TERM EVOLUTION

Numerous characterizations were performed on 120-nm thick evaporated S iO2 layers in order to understand how their features change as a funct ion of deposition conditions and time. Density decreases with increasi ng deposition pressure. It governs all the layer properties (refractiv e index, hardness, and stress). In situ stress measurements show that stress can be divided into intrinsic and water-induced components, res pectively linked to local density (outside the pores) and porosity. In trinsic stress increase with decreasing pressure is explained by a dim inution of the Si-O-Si bond angle (IR measurements). Long-term evoluti on is characterized by stress relaxation related to Si-O-Si strained b ond hydrolysis. (C) 1996 Optical Society of America