Ultra Low-Noise Readout for a MEMS Epitaxial Polysilicon Temperature Sensor

This work discloses the development of an ultralow- noise readout for a polysilicon-MEMS-based temperature sensor. The system relies on a multi-mode resonator realized in a conventional epitaxial polysilicon process, and exploits the slightly different temperature dependence of the resonance frequency of a flexural mode and a torsional mode. Instead of using the consolidated relative counting method, widely discussed in the literature, the system employs a single free-running counter and retrieves the temperature information after a discretetime derivative operation. This enables shaping of quantization and phase noise at high-frequency, then filtered by a secondorder low-pass filter. The residual experimental white noise floor is measured as about 0.001 °C/ √ Hz, representing a 30-fold improvement with respect to previous work.