Influence of rf substrate bias on density and mechanical properties of sputtered SiO2 thin films for SAW applications

Amorphous SiO2 layers have been deposited on silicon and glass substrate by reactive magnetron sputtering. The influence of rf substrate bias on coating density and on further mechanical properties of the thin films as e.g. mechanical stress, hardness and Young's modulus was investigated. The results are correlated to a variation of the Si-O-Sibinding angle caused by the densification of the material. The precise adjustment of these thin film properties opens a wide potential for reactive sputtered coatings for ambitious applications such as e.g. surface acoustic wave (SAW) filters.