High Frequency LiNbO₃ Bulk Wave Resonator

Abstract

Bulk Acoustic Wave Resonators made of lithium niobate thin films obtained by layer transfer techniques relied so far only on full sheet buried electrodes, what is impractical in vue of proper filter implementations. In this work, we introduced patterned bottom electrodes and a sacrificial layer cavity along with a Smart CutTM process. We demonstrate Film Bulk Acoustic Resonators (FBAR) with resonance frequencies in the 2.4 GHz range, electromechanical coupling factors in excess of 39 % and quality factors above 250. This paves the way for introducing high piezoelectric coupling factor monocrystalline materials inside thin film BAW devices.