Piezoelectric-on-Silicon Array Resonators With Asymmetric Phononic Crystal Tethering

Abstract

The design, fabrication, and characterization of Piezoelectric-on-Silicon array resonators with asymmetric Phononic crystal (PnC) tethering for applications in high frequency reference oscillators is presented. A hybrid approach of mechanical arraying along with higher mode of operation is used for minimizing the motional resistance. For improving the Q-factor, novel asymmetric PnC tethers are developed that not only exhibit a larger bandgap than their symmetric PnC counterparts, but also have significantly better design optimization capabilities for fine tuning the tether properties. Third order longitudinal mode resonators operating at frequencies of ~300 MHz with and without PnC tethering and with different number of resonators in the array were fabricated using $2~\mu \text{m}$ SOI wafers. The measured characteristics of the resonators showed a peak unloaded Q-factor of 4454 and a motional resistance of 200 $\Omega $ at 312 MHz for a seven resonator array. These results are comparable with the best reported in literature, in spite of a lesser silicon thickness. [2016-0194]