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.