Transverse-Mode Spurious Suppression Technique for Surface Acoustic Wave Resonator with Zero Temperature Coefficient of Frequency on a SiO₂/Al/LiNbO₃ Structure

Abstract

In this paper, we describe a suppression technique of transverse-mode spurious responses for a surface acoustic wave (SAW) resonator with a near zero temperature coefficient of frequency (TCF) on a SiO 2 /Al/LiNbO 3 structure. We investigated the thinning of SiO 2 on the dummy electrode region and studied how the transverse-mode responses change with remaining SiO 2 thickness h on the dummy electrode region. As the results, we clarified that the remaining SiO 2 thickness h on the dummy electrode region has an optimum value and could suppress the transverse-mode spurious responses completely when H and h are set at 0.35 λ and 0.20 λ, respectively. It was demonstrated that the selective SiO 2 removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO 2 /Al/LiNbO 3 structure for a wide range of SiO 2 thicknesses, provided that the SiO 2 thickness at the dummy electrode region is adjusted properly.