Stress evaluation of RF sputtered silicon dioxide films for MEMS

In the present work, the stress evaluation of RF sputtered silicon dioxide films for MEMS applications has been reported. The films were deposited in argon atmosphere in the pressure range 5-20 mtorr at 300 W RF power using a 3 inch diameter silicon dioxide target. The stress measurements were carried out using wafer curvature technique. All the deposited films show compressive stress except the film having thickness less than 5000 Å. It is observed that sputtering pressure, film thickness and annealing temperature affect the stress in SiO2 films. The dependence of deposition rate and etch rate on the deposition parameters were also investigated. To obtain the minimum stress in the film, the deposition parameters are optimized. An array of cantilever beams of sputtered silicon dioxide film was fabricated. It was observed that beams up to 500 micron length show no upward or downward bending indicating low stress in the films deposited under optimized conditions.