Suppression of spurious responses near anti-resonance of TC-SAW resonators by selective thinning of SiO₂

This paper discusses the generation mechanism and suppression of spurious resonances near the anti-resonance in temperature compensated surface acoustic wave devices using the SiO 2 /128°YX-LiNbO 3 structure. Detailed field analysis is performed for the spurious resonances, and the result indicates that the spurious modes are caused by excitation and/or scattering near the electrode finger edges, and can be suppressed well by thinning of the SiO 2 layer selectively in the gap region. It is also shown that most of spurious responses can be suppressed for the piston design using the Cu dots with the SiO 2 selective thinning. In contrast, this selective SiO 2 thinning does not work well for the piston design using the Cu stripes.