AlN piezoelectric on silicon MEMS resonator with boosted Q using planar patterned phononic crystals on anchors

We report an approach to suppress anchor loss in thin-film piezoelectric-on-silicon (TPoS) micromechanical (MEMS) resonators by patterning 2D phononic crystals (PnCs) externally on the anchors. The PnCs serve as a frequency-selective reflector for outgoing acoustic waves through the tethers of the TPoS resonator. According to our experimental results, combining the PnCs with the conventional TPoS resonator significantly enhances the quality factor (Q) and correspondingly lowers the insertion loss (IL). The measured improvement is reproducible over multiple samples and consistent with the simulations by tuning the PnC bandgaps, suggesting significant reduction of acoustic leakage to the substrate by adopting the PnCs.