Effects of Substrate Temperature during RF-Sputtering of Silica on Optical and Chemical Properties, and Re-Emission Coefficient

The optical and chemical properties of rf-sputtered silica films have been investigated as a function of film thickness. As the film thickness increases up to 1500 Å, the deposition rate decreases while the etch rate increases. The peak position of absorption near 9 µm for as-sputtered film shifts toward shorter wavelengths with increasing film thickness. This tendency is also observed in the case of heat-treated film, but peak positions shift by smaller amounts than those of as-sputtered film. The above phenomena are closely related to the substrate temperature during the sputtering. Using the absorption coefficient and half-width of the 9 µm absorption-band, the degree of oxygen deficiency is estimated to be 10%. The re-emission coefficient calculated from the film-thickness-dependence of the deposition rate decreases with increasing sputtering voltage.