Transient processes in thin film bulk acoustic wave piezoelectric resonators

ABSTRACTWe studied electrically forced, transient thickness-extensional vibration of piezoelectric plates of crystals of class 6 mm as thin film bulk acoustic wave resonators. A generalized Fourier series solution was obtained and verified by comparison with finite element numerical analysis. The transient processes of the startup or shutting down of a resonator was examined. It was found that for a typical thin film resonator of ZnO or AlN with a 2 µm thickness, a fundamental thickness-extensional frequency of 1–2 GHz, and a damping described by a material quality factor of 105, the characteristic startup time from rest to time-harmonic motion is about 0.1 millisecond.