Electrostatically driven and capacitively detected differential lateral resonant pressure microsensor

Abstract

Presented is the design, fabrication and characterisation of an electrostatic‐driving and capacitive‐detection differential resonant pressure microsensor. The differential structure consists of two resonators immobilised on the diaphragm. In response to the pressure under measurement, the diaphragm deflection increases the intrinsic resonant frequency of one resonant beam and decreases the resonant frequency of the other. A differential frequency output reduces the common frequency drift caused by stresses and interferences, and thus improves the sensor's stability. The device geometries were optimised using numerical simulations and the fabrication process was based on a silicon‐on‐insulator wafer requiring only two masks with simplified microfabrication steps (e.g. sputter, wet etching and deep reactive ion etching). The sensor was quantified in an open‐loop characterisation platform, producing a quality factor higher than 10 430 in vacuum (< 0.5 Pa). Closed‐loop test results recorded a linear resonant frequency shift (a linear correlation of 0.9999) in response to applied pressure, with a sensitivity of 227 Hz/kPa. This resonant pressure microsensor has a simple fabrication process and reliable performance, and can be used for pressure monitoring in various locations including weather stations and aerospace.