Analysis and experiment of HBAR frequency spectra and applications to characterize the piezoelectric thin film and to HBAR design

In this paper, we present the resonance frequency spectra features of a composite resonator consisting of a piezoelectric film and a substrate plate. Based on those features, a direct method to characterize the piezoelectric film with two electrodes is presented. By directly using the parallel and series resonant frequency spectra of the HBAR, the electromechanical coupling factor, the density and the elastic constant of the piezoelectric film can be obtained directly. Some problems related to the accuracy of the method, especially the effect of the electrodes, are discussed.