Comparison of different electromagnetic models of bulk acoustic wave resonators and filters

High-performance and miniatuarized bulk acoustic wave (BAW) devices require accurate and sophisticated computer aided design methods. Different modeling and simulation methods have to be applied depending on the simulated device, its complexity, available computational resources, and required accuracy. In order to model all relevant effects that are important to accurately characterize a device, it is important to know what details to model, how to model them, and to what extent. This paper presents and compares different electromagnetic models of mirror-type BAW resonators that are simulated with a 3D finite element method electromagnetic solver. The impact of meshing effects of the 3D electromagnetic solver on the simulated resonator and filter performances is discussed. Additionally, a simulation method is presented in which the acoustic and electromagnetic effects are simulated together. The combined simulation of the acoustic and electromagnetic effects is accomplished by incorporating the acoustic effects into the electromagnetic simulation by applying a frequency-dependent, complex-valued, equivalent permittivity for the piezo material. For the examined electromagnetic BAW resonator models the electromagnetic effects, computational effort, accuracy, and applicability are discussed. By considering the different enhancements introduced in the proposed electromagnetic BAW models, it is possible to improve the agreement of measurement and simulation.