A Micromachined Resonant Differential Pressure Sensor

This article presents a new micromachined resonant differential pressure sensor, which is mainly composed of an SOI wafer as the sensing element and a glass-on-silicon (GOS) cap for vacuum packaging. More specifically, two resonators were deployed on the central and side areas of the pressure-sensitive diaphragm in the SOI handle layer and coupled to the pressure-sensitive diaphragm in the GOS glass layer, enabling differential outputs. The proposed differential pressure sensor was fabricated based on conventional microfabrication processes (e.g., photolithography, deep reactive ion etching, and anodic boning) and characterized in both open- and closed-loop manners, producing quality factors of the resonators higher than 18 000. Furthermore, averaged differential pressure sensitivities were quantified as -4.4664 Hz/kPa (~64 ppm/kPa) with a linear correlation coefficient of 0.9992 (a static pressure of 110 kPa and a temperature from -30 °C to 80 °C) and -4.4516 Hz/kPa (~64 ppm/kPa) with a linear correlation coefficient of 0.9992 (static pressure from 110 to 310 kPa and temperature of 25 °C). In addition, averaged temperature sensitivities and averaged static pressure sensitivities were quantified as -1.2932 Hz/°C (~18 ppm/°C) and 0.0989 Hz/kPa (~1 ppm/kPa), which further validated the proposed differential pressure sensor.