High Accuracy Resonant Pressure Sensor With Balanced-Mass DETF Resonator and Twinborn Diaphragms

The design and fabrication of a resonant pressure sensor based on balanced-mass double-ended tuning fork resonator with twinborn diaphragms are described. It is shown that the thermal stress and the out-of-plane displacement of the vibrating beams of the resonator could be significantly reduced by adopting some appended structures. The simulation results of the frequency versus pressure relationship of the sensor also match the theoretical analysis over the full scale very well. The sensor is fabricated by dry/wet etching and silicon bonding technology with 4' <;100> silicon structure layer and 7740 glass cap. System in packaging is performed with cuboid glass tube to isolate thermal stress. The vacuum packaged sensor is electrostatically excited to vibration, which yields a high Q-factor of 22795. To compensate and calibrate the sensor under temperature influence, the polynomial algorithm is used. Under self-excited oscillation via an automatic gain control circuit, the sensor is characterized of an experimental maximum error of 0.021%FS over the range 20-185 kPa. Measurements also show a pressure sensitivity larger than 20 Hz/kPa and a zero-load resonant frequency of about 34 kHz. As such, the resonant pressure sensor can be applied in high accuracy pressure measurements.