Silicon-SAW Resonators and Delay Lines based on Sub-micron Lithium Niobate and Amorphous Silicon

This paper presents a new method to improve the performance of SAW devices based on transferred lithium niobate thin films. Amorphous silicon replaces the single-crystal silicon to eliminate a conductive layer generated in the thin-film transfer processes. As a result, the electromechanical coupling of the surface-guided acoustic wave is maximized, and the substrate loss is reduced in the amorphous-silicon-based hybrid wafer. The fabricated resonator shows an extracted electromechanical coupling coefficient of 22% with over 60 dB impedance radio, which is 30 dB higher than the resonator with parasitic surface conductive effect. The fabricated delay lines show excellent propagation properties of the excited surface-guided acoustic wave with a minimum propagation loss of 18.1 dB/mm at 2.35 GHz, which further demonstrate the elimination of the conductive layer and outstanding acoustic energy confinement between lithium niobate and amorphous silicon. This work has shown the strong potential of the silicon-SAW platform for front-end signal processing.