Abstract
This paper presents a resonant pressure microsensor with a wide range of pressure measurements. The developed microsensor is mainly composed of a silicon-on-insulator (SOI) wafer to form pressure-sensing elements, and a silicon-on-glass (SOG) cap to form vacuum encapsulation. To realize a wide range of pressure measurements, silicon islands were deployed on the device layer of the SOI wafer to enhance equivalent stiffness and structural stability of the pressure-sensitive diaphragm. Moreover, a cylindrical vacuum cavity was deployed on the SOG cap with the purpose to decrease the stresses generated during the silicon-to-glass contact during pressure measurements. The fabrication processes mainly contained photolithography, deep reactive ion etching (DRIE), chemical mechanical planarization (CMP) and anodic bonding. According to the characterization experiments, the quality factors of the resonators were higher than 15,000 with pressure sensitivities of 0.51 Hz/kPa (resonator I), −1.75 Hz/kPa (resonator II) and temperature coefficients of frequency of 1.92 Hz/°C (resonator I), 1.98 Hz/°C (resonator II). Following temperature compensation, the fitting error of the microsensor was within the range of 0.006% FS and the measurement accuracy was as high as 0.017% FS in the pressure range of 200 ~ 7000 kPa and the temperature range of −40 °C to 80 °C.
Highlights
Piezoresistive pressure sensors are sensitive to temperature variations and suffer from limited resolutions [18]
In order to address this issue, this study presented a resonant pressure microsensor based on a specific design to downregulate the pressure sensitivities, improve the structural strength of the microsensor and eventually further enlarge the pressure measurement range
(1) introduced the design of the microsensor, (2) estimated maximum stresses under high pressures and obtained frequency responses of the resonant microsensor based on theoretical calculations and numerical simulations, (3) realized the fabrication of the microsensor based on Micro-Electro-Mechanical System (MEMS), (4) validated the microsensor by employing several experiments including open-loop and closed-loop tests
Summary
Chao Xiang 1,2 , Yulan Lu 1,2 , Chao Cheng 1,2 , Junbo Wang 1,2, *, Deyong Chen 1,2, * and Jian Chen 1,2.
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