On the Design of High Overtone BAW Resonators with Enhanced Power Handling

The design of bandpass filters for frequencies above 4GHz is challenged by the opposite scaling rules with frequency between the needed resonator static capacitances and the capacitance per unit area. The latter results in significant decrease of useful device areas in classical BAW resonators at high frequencies, which in turn determines significantly enhanced acoustic power density in those devices. Here we discuss the design of a second overtone BAW resonator and the corresponding filter which alleviates some of the technological challenges of the AlN or AlScN layers with inverted polarities in high overtone BAW stacks.