Reduction of Temperature Sensitivity for Resonant Micro-Pressure Sensor Using Glass-Silicon Coupling Wafer Packaging

Abstract

This article presents a resonant micro-pressure sensor consisted of the resonators positioned on device layer of SOI wafer, which was vacuum packaged by a glass-silicon coupling wafer. Ambient pressure under measurement deflected the pressure-sensitive diaphragm, inducing intrinsic frequency shift of resonators, while the glass-silicon coupling wafer packaging can alleviate the side effect of environmental temperature disturbance, reducing shifts of intrinsic frequency of resonators. Numerical simulations were employed to the design and optimization of sensor where technical issues correlated with strong temperature dependence and improper mechanical coupling were addressed. The developed sensor was fabricated based on conventional microfabrication processes, and characterized with comparison to the counterpart using glass wafer packaging. Characterization results revealed that the temperature sensitivities were quantified as 37.93 Hz/°C vs. 10.36 Hz/°C in the full temperature (−40 °C to 85 °C) range with corresponding eigenfrequency shifts measured as 13.18 Hz vs. 3.75 Hz after 20 temperature cycles, respectively, for the sensors using glass vs. glass-silicon coupling wafer packaging. Meanwhile, under the condition of room temperature with pressure of 10 kPa, 1kPa, and 0.05 kPa, the long-term measurement deviations of sensors over 90 days period were reduced from12.17±2 Pa to3.24±1 Pa with the help of glass-silicon coupling wafer packaging. These results validated that the developed sensor using glass-silicon coupling wafer packaging may be an effective tool in the field of micro-pressure measurements.