Suppression of Lowest-Order Plate Mode in Wafer-Bonded SAW Devices Using LiTaO3 Thin Plate

This paper describes a suppression technique for the lowest-order plate mode in wafer bonded surface acoustic wave (SAW) devices using LiTaO
₃
(LT) thin plate. When LT plate thickness is close to the SAW wavelength, say micron order, the lowest-order plate mode appears near the main resonance. It is shown that the plate mode can be suppressed by choosing LT cut angle, electrode thickness and LT plate thickness properly. It is also shown that when the acoustic length is finite, the leaky nature causes additional loss even when the LT plate is extremely thin. Detailed discussions are also given how the additional loss changes with the plate thickness.