A Resonant Pressure Sensor with Super High Resolution and Stability Based on Novel Volume Shrinkage Method

We have developed a resonant pressure sensor with a super high resolution and an excellent long-term stability that can measure from atmospheric pressure to absolute pressure of 70 MPa (Fig. 1). The sensor consists of a resonator for pressure measuring and for temperature compensation. Each resonator is formed on a cantilever to reduce the effects of strain noise transmitted from the package. In addition, while conventional resonant pressure sensors use a diaphragm structure for pressure/stress conversion, this pressure sensor utilizes silicon volume shrinkage to realize a small variation in pressure sensitivity. The pressure sensitivity of the resonator for pressure measurement was average -2037.4ppm/MPa, and the standard deviation (σ) was 5.8ppm/MPa in 50 sensors. Compensation of pressure and temperature is conducted by using each resonator’s frequency at some appropriate calibration points. The resolution of the pressure output was 10Pa (0.000014% of Full Scale 70MPa). The long-term stability of the sensor was about 40Pa/month (0.0007% of FS/year) or less by comparing to a reference barometer (PACE1000).