Low Temperature 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 (SiO 2 ) 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-strecthing vibration at about 1075 cm1 decreases as the growth temperature is decreased below 1000°C. Comparing the properties of these films with suboxides (SiO x1 x < 2) 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 (SiO 2 ); 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 refraction; and (b) the accompanying decrease in the ir stretching frequency in terms of a decrease in the Si-O-Si bond angle. Accesioni For NTSCRA&i DTIC TAS [] Unannounced 13 Justificatio. -B y .. ............. Distr ibUti~n I A~atlability Codes TV a' or