High-sensitivity Low-noise Multi-axis Capacitive Micro-accelerometers

High performance micro-g resolution small size low cost low power accelerometers are needed in many applications such as inertial navigation Unmanned Aerial Vehicles (UAVs) and GPS augmentation. Several sensing methods have been used including piezoresistive/electric resonant tunneling and capacitive techniques. Capacitive sensing has several advantages in terms of high sensitivity stable DC-characteristics low power dissipation low temperature sensitivity and low noise floor. This research work demonstrates full functionality of high- sensitivity low-noise capacitive multi-axis accelerometers. In order to achieve micro-g resolution two different structures have been utilized: a Silicon-On-Glass (SOG) accelerometer and an all-silicon accelerometer. A monolithic fabrication technique for Post-CMOS MEMS is also developed. Finally a 3-axis single-chip accelerometer is presented. The 3-axis accelerometer shows >3pF/g sensitivity and sub-?g/rtHz mechanical noise floor. The 3-axis accelerometer with the readout circuit provides noise floor of 1.6?g/rtHz and 1.1?g/rtHz for in-plane and out-of- plane devices respectively.