P2G-3 Piezotransduced Single-Crystal Silicon BAW Resonators

We report on the design, fabrication and measurement of 13-MHz piezoelectrically actuated single-crystal silicon beam resonators operating in the first length-extensional mode. The transduction mechanism is based on an aluminum nitride layer grown on top of the resonator beam. The resonators are measured to have a quality factor of Q ~ 20000 at p < 1 mbar and typical motional resistance of R_m ~ 3 kOmega. The electromechanical transduction factor is eta ~20 muN/V, representing a coupling of the same order as produced by 20 V over a 100-nm gap for capacitively coupled resonators. The quality factor is observed to be dependent on the crystal direction of the resonator beam. A qualitative explanation for this effect is given.