Process tolerant design of baw resonators via hole engineering

This paper presents a design approach for a process tolerant design of BAW resonators. Process variations, e.g., etch non-uniformities, affect the edge definition and the exact dimensions of the resonator, and thus impact on the resonance frequency. Through simulation it is demonstrated that a properly designed periodic hole distribution in the bulk of the device can compensate such frequency variations. The perforated resonator is modeled by using effective material properties to make an abstraction of the holes in the resonator. This effective medium model is extended to include the electrostatic spring softening, for which an effective Young´s modulus depending on the applied DC-bias is derived. Finally, results are presented for square lattices of circular and rectangular hole shapes.