Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO₂/LiNbO₃ Structure

Abstract

This article proposes a double metal dots interdigital transducer (IDT) configuration for suppression of spurious responses in temperature-compensated surface acoustic wave (SAW) resonators employing the SiO2/LiNbO3 structure. The proposed IDT configuration includes primary metal dots at the edges of the IDT aperture region, and in addition, secondary metal dots placed near the busbars with the addition of short dummy electrodes. This double metal dots IDT configuration enables us to effectively suppress two kinds of spurious resonances: the transverse resonances that are common and the ones that are predominantly excited in the gap regions between IDT finger edges and busbars. The impact of geometric parameters on suppressing spurious responses is studied using periodic 3-D finite element simulations. Then, it is shown both theoretically and experimentally that the proposed mechanism can effectively suppress almost all spurious responses without affecting the critical performance metrics such as the quality factor and electromechanical coupling coefficient.