A Resonant Pressure Microsensor With a Stress Isolation Layer

This paper presents a resonant pressure microsensor composed of a glass cap for hermetic package, an SOI layer with sensing elements and a glass base for stress isolation. Tested pressure under measurement bends the pressure sensitive diaphragm, producing frequency shifts of underlining resonators while the stress isolation layer can work as a cushion layer to minimize environmental temperature and mechanical disturbances. Numerical simulations were conducted, finding that the stress isolation layer can decrease the axial stresses of the resonators from +16 to +2 MPa (high-temperature challenging), from -12 to -5 MPa (low-temperature challenging), and from 2.5 to 0.5 MPa (mechanical challenging). The proposed microsensor was fabricated based on conventional microfabrication and characterized with comparison to the counterpart without the stress isolation layer, producing an accuracy of 0.01% FS vs. 1% FS, a temperature shift of 37 ppm versus 10088 ppm, a pressure shift of 45 ppm versus 777 ppm, a temperature hysteresis error of 21 ppm versus 187 ppm, a pressure hysteresis error of 22 ppm versus 265 ppm, a temperature repeatability error of 15 ppm versus 703 ppm, a pressure repeatability error of 21 ppm versus 36 ppm, and a long-term stability of >7 months versus 69 days. These results validated the functionality of the proposed resonant pressure microsensor with the stress isolation layer, which may be potentially used as an effective tool in the fields of aerospace aviation, industrial control, and meteorological monitoring.