A study of voids in sputtered SiO2

Abstract

Voids have been observed in sputtered SiO2 films when deposited over substrate topographies with high aspect ratios (depth/width). This report describes experimental results which show the conditions under which voids are found, and the response of void formation to available deposition parameter variations, such as resputtering bias, power, and frequency. A simple model for void formation is used to predict quantitatively the limits of the process with respect to void formation. The results show that it is possible to obtain void-free coatings up to an aspect ratio of ∼2.0, and that the controlling factor is the sputtering yield versus angle of incidence curve. Data suggest that 40-MHz conditions are slightly more favorable than 13 MHz.