Linear acoustic bandgap arrays for spurious mode suppression in piezoelectric MEMS resonators

In this work, we present a technique that utilizes arrays of coupled-ring linear acoustic bandgap (LAB) structures, which exhibit characteristic frequency stop bands, to reduce spurious modes in the wide-band response of AlN-on-Si lateral mode resonators. Aggressive LAB tethering (one support per finger) of high-order modes yields an increase in atmospheric quality factor (Q) from 1860 to 2890 for the designed peak at 209 MHz, compared to resonators with traditional tethers. Spurious modes from 0 to 360 MHz are suppressed by at least 30 dB relative to the main peak. The LAB structures presented achieve this goal through a combination of complete acoustic bandgaps and deaf bands.