Differential-capacitive-input and differential-piezoresistive-output enhanced transduction of a silicon bulk-mode microelectromechanical resonator

Parasitic capacitive feedthrough poses a challenge typical to electrical detection of resonance in micron (and even more so for nano) scale silicon-based mechanical resonant devices. The most efficient methods of capacitive transduction solely address the issue of feedthrough at most and with preference for certain vibration mode shapes. In this work, we present an electrical characterization configuration that allows both a substantial degree of feedthrough cancelation (by as much as 53 dB) and an increase in the electromechanical coupling by use of piezoresistive sensing. Due to the balanced setup, parasitic feedthrough associated with the transducers is canceled at both the input and output interfaces. The figure of merit, given by the ratio of the resonant peak value to the direct feedthrough is increased by 67 dB from applying the proposed transduction setup. Variations in the effect of feedthrough cancelation through this configuration are analyzed and studied experimentally. Although demonstrated for breathing mode square-plate resonators in this paper, the technique can be extended to any topology given an even number of electrodes usable for capacitive actuation.