Analysis and Elimination of the Capacitive Feedthrough Current on Electrostatically Actuated and Sensed Resonance-Based MEMS Sensors

This paper presents the investigation of two different capacitive feedthrough current elimination methods with an analysis of the effect of the capacitive feedthrough current on the resonance characteristics of electrostatically actuated and sensed resonant MEMS sensors. Electrostatically actuated and sensed resonators have various applications, such as accelerometers, gyroscopes, mass sensors, and temperature sensors. In most of these applications, as sensitivity increases, gain decreases. The capacitive feedthrough current between the drive and sense electrodes disturbs the resonance characteristics of the resonator, especially when the gain is rather small. In order to eliminate the dominating feedthrough current in such cases, two methods were proposed. In the first method, differential input signals were applied to two separate resonators, one active and one passive, sharing the same sense electrode. Although this method seems to be easily applicable to all types of resonators, this study has shown that mismatches between the resonator pair prevent perfect elimination of the feedthrough current. In the second method, a novel lateral electrostatic resonator with differential sense electrodes was designed and fabricated to eliminate the feedthrough current. Measurements showed that the feedthrough effect was successfully eliminated and 27 times higher SNRdB was achieved with this method. Moreover, it was successfully demonstrated that any mismatch can be compensated by a simple resistive adjustment.