Ultrathin single‐crystalline LiNbO ₃ film bulk acoustic resonator for 5G communication

Abstract

This Letter reports a high‐performance film bulk acoustic resonator (FBAR) that can be applied in 5G wireless communication. The FBAR has a back‐etched free‐standing structure using an ultra‐thin single‐crystalline lithium niobate (LiNbO 3 ) as the piezoelectric film. The thin LiNbO 3 was obtained by the smart cut method and FBARs were fabricated by a standard MEMS process. Owing to the superior bulk‐like properties of the single‐crystal thin film, the fabricated FBARs have a resonant frequency of 5.0 GHz, a quality factor above 1800 and an electromechanical coupling coefficient of 2.66%, demonstrating a promising potential of FBAR filters in 5G and future 6G applications.