An out-of-plane "hinge-shaped" nano-gap accelerometer with high sensitivity and wide bandwidth

This paper presents the design, fabrication, and characterization of a novel “hinge-shaped” out-of-plane differential accelerometer utilizing nanometer sensing gap (300 nm) electrodes. The increased electromechanical coupling provided by narrow gap allows the design of micro-g accelerometers with high resonant frequency (> 10 kHz), which would extend the operational bandwidth as well as the input acceleration range compared to conventional devices. Furthermore, the proposed design provides an increased immunity against stiction without reducing device sensitivity. The out-of-plane accelerometers are fabricated on a 60 μm thick silicon-on-insulator (SOI) wafers, and subsequently interfaced with the readout electronics to fully characterize its performance. Measurement results show a scale factor of 1.266 V/g, noise density level of 72.05 μg/.Hz at 1 Hz, bias drift of 106.57 μg, and velocity random walk (VRW) of 50 μg/.Hz. The noise floor of the device can be improved to better than 10 μg/.Hz by packaging the current design in vacuum, without facing any stability issues.