Q-enhancement with electrode materials in the FBAR for timing devices

Thin film bulk acoustic resonators (FBARs) are key components in the timing devices such as FBAR-based voltage controlled oscillators (VCOs) or wake-up-circuits for wireless sensor nodes. For such applications, theoretical analysis of Q-factor is crucial rather than that of the effective electro-mechanical coupling coefficient k
_eff
²
. We developed the batch calculation program based on Mason's model in this study. Since the physical model in our program was not constrained by the element size against the finite element method (FEM), resonant frequency and characteristic impedance, which strongly affect the Q-factor, can be easily kept a constant in the calculation models. Thus, their influences for the Q-factor can be cancelled. It was clarified how Q-factor is controlled by the electrode design.