Electrical characterization, crosstalk compensation and experimental examination of AlN-based piezoelectric micro resonators

Abstract

Aluminum nitride based micro resonators are fabricated and measured with an all-electrical excitation and detection method in this paper. Low resistivity single crystal silicon is used as resonating element, serving simultaneously as bottom electrode for the piezoelectric layer. The elimination of the bottom metal electrodes reduces the number of stacked layers and stress in the cantilever; however, the short circuit connection between drive and sense port silicon grounds induces serious feedthrough capacitance effect. Electrical measurement results indicate that, the resonator output is a superposition of mechanical resonance behavior and electrical crosstalk from feedthrough capacitance. A general equivalent circuit model is derived to analyze the resonator’s electromechanical performance. To eliminate the electrical crosstalk, a compensation solution has been developed, by applying an inverted adjustable voltage to the common bottom electrode. Further experimental investigations of the device under different controlled pressures show that, the output amplitude after compensation is precisely symmetric around the resonance peak, and phase shift of -90° occurs at resonance, indicating that the feedthrough has been adequently cancelled out.