AlN-on-Si MEMS resonator bounded by wide acoustic bandgap two-dimensional phononic crystal anchors

We report an AlN-on-Si Lamb wave resonator with a unique wide acoustic bandgap (ABG) phononic crystal (PnC) structure at its anchors that provides an almost 4-fold increase in quality factor (Q). We show that the wider ABG provides for greater suppression of anchor loss and thus higher Q relative to a narrower ABG. Compared to more common circular void PnC structures, the unique PnC structures presented herein based on solid disks offer a 9-fold increase in the ABG size (82MHz vs. 9MHz) at a similar center frequency around 142MHz. The measured improvements in Q over multiple devices are consistent with finite element simulations on tuning the ABG size.