Low Temprature Growth of Silicon Dioxide Films: A Study of Chemical Bonding by Ellipsometry and Infrared Spectroscopy.

This paper presents a spectroscopic study using the techniques of ellipsometry and infrared ir absorption spectroscopy of the chemical bonding in silicon dioxide SiO2 films grown in dry oxygen ambients at temperatures between 550 and 1000 C. We find that the index of refraction at 632.8 nm increases and the frequency of the dominant ir active bond-stretching vibration at about 1075cm decreases as the growth temperature is decreased below 1000 C. Comparing the properties of these films with suboxides SiOx, x grown by plasma enhanced chemical vapor deposition PECVD, and compacted bulk silica has lead us to conclude a that films grown at temperatures at or below 1000C are homogeneous stoichiometric oxides SiO2 and b that the systematic and correlated variations in the index of refraction and the ir frequency result from increases in the film density with decreasing growth temperature. We present a microscopic model that accounts for a the increases in the density and the index of refractions and b the accompanying decrease in the ir stretching frequency in terms of a decrease in the Si-O-Si bond angle.