A high-sensitivity silicon accelerometer with a folded-electrode structure

A high-sensitivity capacitive silicon accelerometer with a new device structure is presented in this paper. The structure uses a fixed rigid electrode suspended between a proof mass and a stiff moving electrode to provide differential capacitance measurement and force rebalancing. High sensitivity is achieved by forming a thick silicon proof mass and a narrow uniform air gap over a large area. The mechanical noise floor is reduced by incorporating damping holes in the electrodes. The accelerometer structure is all silicon and is fabricated on a single silicon wafer. The measured sensitivity for a device with 2.6 mm × 1 mm proof mass and 1.4 μm air gap is ≈11 pF/g per electrode. The calculated mechanical noise floor for the same device is 0.18 μg/√Hz at atmosphere.