Effect of Ultraviolet Irradiation on the Optical Properties of Silicon Oxide Films

Abstract

The effect of ultraviolet irradiation on the optical properties, thickness, and chemical composition of silicon oxide films prepared by evaporation of silicon monoxide in the presence of oxygen was studied. The films were prepared at deposition rates of 2 Å/sec to 6 Å/sec and at pressures of 7−9 × 10−5 torr of oxygen. Ultraviolet irradiation with quartz mercury lamps eliminated the initially high ultraviolet absorptance of such films completely and changed their refractive index, thickness, and weight by as much as 10%. Two completely different effects were found to be responsible for the changes in the films caused by ultraviolet treatments: (1) ultraviolet irradiation rearranges the oxygen gettered during the evaporation process and forms well-defined silicon oxide with low ultraviolet absorptance and (2) treatment in air or oxygen increases the oxygen content in the deposited film.