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

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, SiO2 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 SiO2 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 SiO2 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.