Prediction of BAW resonator performance using experimental and numerical methods

Filters based upon bulk-acoustic-wave (BAW) resonators are attractive for a variety of RF applications. To satisfy the ambitious specifications and to facilitate a fast and cost economic design, we present an efficient simulation strategy combining different modeling approaches. First, a 1D transmission line model (Mason model) is used to construct the layer stack to meet the desired resonance frequencies and bandwidth. Second, the system of Newton's equation of motion and Maxwell's equations coupled by the piezoelectric effect is solved by FEM simulations. Thus, the lateral structure, e.g., a specific border region, can be designed to maximize the Q-value and to minimize the excitation of spurious modes. The theoretical predictions are excellently confirmed by electrical measurements and laser interferometry. Typical technological features, such as processing-related non-uniform thicknesses, and their impact on the resonance characteristics are analyzed by numerical simulations.