Optimization of Edge Profile for Improved Anti-Resonance Quality Factor in Lithium Niobate SH0 Resonators

Thin-film lithium niobate (LNO) has been identified as a promising material platform for enabling high electromechanical coupling and low-loss piezoelectric resonators for filtering applications. In this work, the design and fabrication of fundamental shear horizontal (SHO) mode resonators with a resonance frequency of 1.1 GHz are reported. Initial devices show high losses leading to low quality factor at anti-resonance due to undesired redeposition debris originating from Ion Beam Etching (IBE) of the resonator sidewalls. Methods to improve the quality of the resonator sidewalls and minimize those losses are presented. With those improvements, SHO resonators with high electromechanical coupling $(k_{eff}^{2}$ = 28%) and impedance ratios larger than 104 could be achieved.