Vibration mode analysis of RF film bulk acoustic wave resonator using finite element method

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in a few of GHz frequency region have been analyzed by its impedance analysis using the finite element method. These characteristics could be calculated from solving an large eigen value problem formulated by using electromechanical wave equations and its boundary conditions. In particular, the spurious characteristics as well as all resonant modes and mode shapes, considering the effects of electrode area variation, was extracted. From this result, the fact was obtained that the optimum ratio of length and thickness at the simplified resonator structure is 20:1 and the minimum ratio is 5:1 to operate fundamental thickness vibration mode. Then, we compared our results with the simulation data obtained by Mason model analysis and the measured data of the zinc oxide (ZnO) film bulk acoustic wave resonator (FBAR).