Highly improved quality factor of the film bulk acoustic wave resonator by introducing a high quality ZnO buffer layer

Abstract

The inferior film quality of sputtered AlN has hindered the further development of high-performance film bulk acoustic wave resonators (FBAR). In this work, the ZnO buffer layer was introduced into the FBAR to improve the performance of FBAR for the first time. Compared with its counterpart without the buffer layer, the devices with a buffer layer exhibited a far higher average quality factor (2π times the maximum energy stored in the FBAR/energy dissipated per period) of 2575 ± 136, which was about 64 % larger than that without a buffer layer. Benefiting from the enhanced crystalline quality of AlN, the device also showed an improved effective electromechanical coupling coefficient.