High-sensitivity differential fringe-field MEMS accelerometers

Fringe-field capacitive sensing has a potential interest for the inertial MEMS community as it decouples the sensing direction from the pull-in direction, and it is therefore intrinsically immune from this issue. This paper presents a MEMS accelerometer based on fringe-field sensing, that exploits a surface micromachining process with very thin planar interconnections (<; 4 μm). As these interconnections are exploited to create the fringe fields used for sensing, the possibility to increase their density directly increases the sensitivity. The experimental results demonstrate a value of about 6 fF/g with a device resonance frequency around 850 Hz and a quality factor around 4, for a device area of (450 × 600) μm².