Simulation of high-Q thin film bulk acoustic wave resonator for chip-scale atomic clock

Abstract

Thin Film hulk acoustic wave resonators (FBARs) with relatively high Q-factor are considered good candidates to be used in the radio frequency module of chip-scale atomic clocks. In previous works, SiO 2 thin film was introduced into the FBARs between the top electrode and piezoelectric layer which resulted in a good improvement in Q-factor about 350 after parameters optimization. Based on the same method herein, the SiO 2 thin film is introduced into the FBARs between the piezoelectric layer and bottom electrode. The parameters optimization results show that it can also improve the Q-factor. The FBAR device resonating at 4.6GHz with Q-factor 754 is achieved and the thickness of the SiO 2 thin film and piezoelectric layer of the FBAR are 0.4um and 0.63um respectively. The optimized Q-factor of the FBAR device in this work is about 127 higher than that in the previous works, and it is expected to be used in chip-scale cesium atomic clocks.