Simultaneous interrogation of high-Q modes in a piezoelectric-on-silicon micromechanical resonator

A piezoelectric-on-silicon micromachined square plate resonator for the simultaneous excitation of three bulk acoustic wave modes lying within a frequency span of 2.84-3.2 MHz is reported. Three resonant modes are electrically interrogated in this frequency span, with two bulk acoustic wave mode types (Square-extensional and Lamé) well-established for this system while the third is a higher frequency mode which has not been addressed before via capacitive or piezoelectric actuation schemes. This mode was found to have a high quality factor, similar temperature co-efficient of frequency and a comparable thin-film mass sensitivity as compared to the other modes. An electrode/transducer configuration to enable selective actuation and/or suppression of the actuated in-plane modes is also reported.