Suppression of transverse-mode spurious responses for zero temperature coefficient of frequency SAW resonator on a SiO2/Al/LiNbO3 structure

This paper describes a suppression of transverse-mode spurious responses for zero temperature coefficient of frequency (TCF) surface acoustic wave (SAW) resonator on a SiO₂/Al/LiNbO₃ structure. We investigated to use thinning of SiO₂ on the dummy electrodes and studied how the transverse-mode responses change with remaining SiO₂ thickness h on the dummy electrode region. As the results, we could realize high performance SAW resonator with complete suppression of the transverse-mode spurious responses when h is set at 0.20λ. It was demonstrated that the selective SiO₂ removal technique is effective to suppress transverse-mode spurious responses for SAW resonators employing the SiO₂/Al/LiNbO₃ structure for wide range of SiO₂ thicknesses, provided that the SiO₂ thickness at the dummy electrode region is adjusted properly.