Multipurpose Acoustic Metamaterial Anchors for Aluminum Scandium Nitride Contour Mode Resonators

We present a new design for AlScN contour-mode-resonators (CMRs) operating in the radiofrequency (RF) range. This design relies on acoustic metamaterials (AM) based lateral anchors to greatly enhance the power handling compared to conventional CMR-designs. Such anchors generate acoustic stopbands that prevent the leakage of piezo-generated acoustic energy from the resonating body into the substrate. The AM anchors reported in this work consist of the same AlScN film as in the CMRs' active region, combined with a periodic array of rods. Their use allows a reduction of CMRs' thermal resistance with respect to conventional designs, and enables a significant temperature compensation. As a result, the CMRs with AM anchors reported in this work show a $\sim$ 60% reduction in their Duffing coefficient with respect to conventional designs with fully-etched lateral sides, hence an improved linearity. Furthermore, when used to set the output frequency of high-power feedback loop oscillators, the CMRs with the AM anchors reported here enable a lower phase-noise compared to what achievable when employing the conventional counterparts. 2024-0053