Design and Fabrication of S0 Lamb-Wave Thin-Film Lithium Niobate Micromechanical Resonators

Commercial markets desire integrated multifrequency band-select duplexer and diplexer filters with a wide fractional bandwidth and steep roll-off to satisfy the ever-increasing demand for spectrum. In this paper, we discuss the fabrication and design of lithium niobate (LN) thin-film S₀ Lamb-wave resonators on a piezoelectric-on-piezoelectric platform. Filters using these resonators have the potential to fulfill all the above requirements. In particular, we demonstrated one-port high-order S₀ Lamb-wave resonators with resonant frequencies from ~400 MHz to ~1 GHz on a black rotated y-136 cut LN thin film. The effective electromechanical coupling factor (k²_eff ) ranges from 7% to 12%, while the measured quality factor ranges from 600 to 3300. The highest k²_eff × Q achieved on this chip is 194, significantly surpassing contour mode resonators manufactured in other technologies.