MEMS resonators with electrostatic actuation and piezoresistive readout for sensing applications

MEMS resonators based on internal thermal-piezoresistive amplification are a suitable alternative for sensing applications since they enable high resonance frequencies and high Q-factors. In this work, the principle of operation of this amplification mechanism is modeled, using analytical and lumped methods, based on previous reports found in the literature. For a better understanding of the several domains involved in the principle of operation of the internal thermal-piezoresistive amplification mechanism, MEMS resonators with electrostatic actuation and piezoresistive readout and with single- or double-mass, were fabricated and experimentally characterized. This mechanism is quite sensitive to variations of the structure geometry or its environmental conditions. Moreover, despite several sources of error have been identified, the model for the single-mass resonator (SMR) fits quite well the experimental results. However, these errors prevented confirming whether the double-mass resonator (DMR) behaves according to the model developed. The DMR performed better than the SMR, achieving higher resonance frequency, higher Q-factor, and higher amplification in vacuum. This set of simulation and experimental results can be used to design novel high-frequency resonators for sensing applications with improved performance due to the Q-factor enhancement achieved by the internal thermal-piezoresistive amplification mechanism.