Transduction performance of piezoresistive silicon nanowires on the frequency resolution of a resonant MEMS sensor

In this paper, we study the resonance frequency resolution of a MEMS resonator based on suspended piezoresistive silicon nanogauges transduction. Nanowire strain gages are attractive for MEMS resonators thanks to their high sensitivity to motion. They have excellent force sensitivity due to their small cross-section area (250×250nm2) and a negligible footprint. Hence, this transduction mean exhibits a very high signal to noise ratio (SNR) of 115dB above a few kHz, which does not limit the excellent resolution frequency required for high performance applications. Thus, resolution frequency down to 35 ppb is here reported, limited by thermo mechanical fluctuations, instrumentation noise and environment stability. Influence of various actuations and damping conditions are investigated and then compared to the Robins´ law that estimates resolution for the frequency measurement. Thus, Robin´s law is validated for the nanogauge transduction of a MEMS resonator. Eventually, these results can be used to anticipate the outstanding frequency resolution of an ongoing resonant pressure sensor, which has been estimated at only a few ppb.