Thermal-Piezoresistive SOI-MEMS Oscillators Based on a Fully Differential Mechanically Coupled Resonator Array for Mass Sensing Applications

A mechanically coupled array technique to enable a fully differential operation of single-crystal silicon thermal-piezoresistive resonators (TPRs) has been demonstrated to alleviate resistive feedthrough issues often seen in TPRs, therefore, featuring clear resonance behavior with decent signal-to-feedthrough ratio. The proposed thermal-piezoresistive dual-II-BARs exhibits feedthrough reduction of more than 67 dB, and no spurious mode, is found within a wide frequency span. The resonator array together with board-level sustaining circuitry also works as a thermal-piezoresistive oscillator (TPO) and demonstrated its performances for real-time mass sensing. Finally, the proposed TPO mass sensor possesses several key features, including real-time monitoring, fast response time, and most importantly, excellent mass resolution of only 83 fg extracted from the measured TPO's Allan deviation.