Toward Band n78 Shear Bulk Acoustic Resonators Using Crystalline Y-Cut Lithium Niobate Films With Spurious Suppression

This work presents the study of suspended Y-cut Lithium Niobate shear bulk acoustic resonators for wide band filter applications in the frequency range of 3.5-4.5GHz. The resonators consist of a Lithium Niobate film with Aluminum top interdigitated electrodes (IDE) and floating bottom metal plate. Through vertical electric field excitation, shear bulk acoustic waves are generated in each unit cell of the device functioning as a quasi-independent resonator. Measured devices at 3.7GHz having large relative resonance-antiresonance bandwidth of 16.7% (750MHz), with 2 Omega impedance at resonance are presented. Suppression of higher order lateral harmonics through etching of trenches in the Lithium Niobate and geometric optimization is discussed.