Finite Element modelling of a thin-film bulk acoustic resonator (FBAR)

The paper aims to propose a three-dimensional (3D) finite element analysis to evaluate the electrical performances of a FBAR (thin-film bulk acoustic resonator) resonator. The piezoelectric theory that uses an equivalent circuit is able to evaluate the thickness-extensional vibration modes in simple 1D configuration but it is not adequate to predict spurious modes with lateral wave vector. Therefore, a fully 3D finite element analysis has been carried out to evaluate the characteristics of a real FBAR prototype that has been fabricated in a research center. The measured characteristics of the FBAR prototype are compared with simulations obtained by the 3D finite element analysis. The agreement between experimental and numerical results confirms the accuracy of the proposed technique. The paper proposes a 3-D numerical approach to design and analyze the electrical characteristics of a real FBAR which has been fabricated following the guidelines obtained by the proposed numerical design.