Thermal Resilience of Suspended Thin-Film Lithium Niobate Acoustic Resonators up to 550 °C

This paper reports a suspended thin - film lithium niobate (LN) piezoelectric resonator platform surviving high annealing temperatures of 550°C, among the highest temperature at which the thermal resilience of suspended LN resonators is studied. Acoustic resonators are built on 600 nm thick transferred stoichiometric LN on silicon wafers with 40 nm thick platinum (Pt) electrodes, selected for high temperature operation. The fabricated resonators are first annealed at 250°C, and the anneal temperature is incrementally increased to 550 °C after 7 rounds of annealing. The annealing is shown to upshift resonant frequencies and can increase the quality factor ($Q$), within a temperature range, before it gradually damages the device performance. This work presents promising results for using the suspended thin-film LN platform for resonators, sensors, and transducers in harsh thermal environments.