Active and Inactive Frames Improve Figure of Merit of Two Dimensional Mode Resonators

This paper introduces a new technique to enhance the figure of merit (FoM) of aluminum nitride (AlN) two dimensional mode resonators (2DMRs). This approach relies on the inclusion of metal frames at the edges of the electrode gratings and between each resonator finger to increase the compliance of these regions. In this way, the vertical displacement component resembles a quasi-square wave under the electrodes, boosting the electromechanical coupling (kt ²), and the lateral displacement component stays confined within each finger, boosting the quality factor (Q). To demonstrate the proposed technique a 1-finger framed 2DMR operating at 2. 35GHz is simulated. By properly designing the metal frames and assuming uniquely acoustic losses, k_t²=7% and Q=1300, which results in a FoM=91 (74% larger than the one previously reported).