A Wafer-Level Packaged CMOS MEMS Pirani Vacuum Gauge

• Published in: IEEE transactions on electron devices 2021-10, Vol.68 (10), p.5155-5161
• Main Authors: Xu, Wei, Wang, Xiaoyi, Pan, Xiaofang, Bermak, Amine, Lee, Yi-Kuen, Yang, Yatao
• Format: Article
• Language: English
• Subjects: Circuits; CMOS; CMOS MEMS; Internet of Things; Microelectromechanical systems; Micromechanical devices; Pirani; Pirani gages; Resistance; Sensors; Silicon; Temperature measurement; Temperature sensors; Thermal conductivity; thermistor; Thermistors; Vacuum gages; vacuum gauge; wafer-level packaged; Wiring
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2021.3103486

In this article, we report a wafer-level packaged Pirani vacuum gauge using the proprietary InvenSense CMOS MEMS technology. The micro Pirani vacuum gauge features three serpentine-shaped molybdenum thermistors on the suspended silicon-on-insulator (SOI) bridges, while the wiring gap of each serpentine-shaped silicon microbridge is 1.6 { {\mu }}\text{m} . For the vacuum range of 5\times 10^{-{4}} -760 Torr, the CMOS MEMS Pirani gauge configured with a constant temperature interface circuit achieves a sensitivity of 0.414 V/Torr in a very fine vacuum regime, while its heating power is less than 21.3 mW. Moreover, the measured output of the micro Pirani gauge shows good agreement with a semi-empirical model, while the model predicts that the proposed Pirani gauge can measure a vacuum pressure as low as 2.6\times 10^{-{4}} Torr. The performance achieved by this Pirani vacuum gauge combined with its high level of integration makes it a promising Internet of Things (IoT) sensing node for vacuum monitoring in the industry.