A High-Sensitivity Resonant Differential Pressure Microsensor Based on Bulk Micromachining

Abstract

This paper presents a high-sensitivity micromachined resonant differential pressure sensor based on bulk silicon. The sensor includes a sensing unit made of a SOI wafer, which is vacuum packaged by a glass-on-silicon (GOS) wafer. More specifically, two resonators located in the SOI device layer were coupled to the GOS glass layer and deployed on the central and side areas of the pressure-sensitive diaphragm respectively, enabling differential outputs. According to the relevant theory of elasticity, the differential pressure sensitivity is high, where the conversion efficiency of the differential pressure to resonators stress is improved by the special cap design, large pressure-sensitive diaphragm and narrow resonators. The developed differential pressure microsensors were manufactured leveraging well-established microfabrication steps including lithography, etching and boning. Characterization of the micromachined sensors was conducted, reporting averaged differential pressure sensitivities of 1) -143.17 Hz/kPa (~2051 ppm/kPa) and a linear correlation coefficient of 0.999992 under a static pressure of 110 kPa and a temperature range from -°C to 40°C; 2) -143.36 Hz/kPa (~2051 ppm/kPa) and a linear correlation coefficient of 0.999997 under a static pressure range from 110 kPa to 250 kPa and a temperature of 25°C. Compared to previous study, the high differential pressure sensitivity of the sensor can pave ways for the subsequent high-precision measurement of differential pressures, which can be used to measure micro differential pressure in the field of nuclear power.