Aluminum Nitride MEMS Resonant Pressure Gauges Without Vacuum Packaging

This letter introduces a micro-electromechanical system (MEMS) resonant pressure gauge based on aluminum nitride piezoelectric resonators that can operate in an atmospheric environment. The pressure is measured in terms of the change in the resonant frequency of a double-ended tuning fork (DETF) resonator, where the aluminum nitride thin film serves as both a piezoelectric layer and a passive layer. The resonator exhibits a resonant frequency of 719 kHz and a Q value of 1764 in air. To our knowledge, this Q value surpasses those of previously reported in-air MEMS DETF resonators that operate in the 100 kHz frequency range. The electronic oscillator circuit for the resonant sensor exhibits a phase noise level of -120 dBc/Hz. The measured sensitivity is 16.8 Hz/kPa within the pressure range of 0-90 kPa, which is consistent with the simulation results obtained from finite element modeling. The resolution of the sensor is 14.9 Pa based on Allan variance measurements. This work thus demonstrates a new class of MEMS sensors for use in harsh environments.