Sub-micro-gravity capacitive SOI microaccelerometers

The implementation and preliminary characterization of a new in-plane capacitive microaccelerometer with sub-micro-gravity resolution (<200ng/√Hz) and very high sensitivity (>15pF/g) is presented. The accelerometers are fabricated in thick (>100 μm) silicon-on-insulator (SOI) substrates using a 2-mask fully-dry-release process that provides large seismic mass (>10 mg), reduced capacitive gaps, and reduced in-plane stiffness. The fabricated devices were interfaced to a high resolution switched-capacitor CMOS IC that eliminates the need for area-consuming reference capacitors. The measured sensitivity is 83 mV/mg (17 pF/g) and the output noise floor is -91 dBm/Hz at 10 Hz (corresponding to an acceleration resolution of 170 ng/√Hz). The IC consumes 6 mW power and measures 0.65 mm² core area.