Abstract
Disclosed is a novel three-axis capacitive-type accelerometer implemented on SOI wafer. The accelerometer consists of four springs, one proof mass, four pairs of gap-closing sensing electrodes (each pair of gap-closing sensing electrode containing one movable electrode and one stationary electrode), and several metal-vias as the electrical interconnections. The movable electrodes are on the proof mass, whereas the stationary electrodes are fixed to the substrate. The three-axis accelerometer has five merits. (1) The sensitivity of the accelerometer is improved since the proof-mass is increased by containing both device and handling silicon layers; (2) The sensitivity is also improved by the gap-closing differential capacitive sensing electrodes design; (3) The parasitic capacitance at bond pad is reduced by the existing of metal-vias between the device Si layer and handling Si layer; (4) The sensing gap thickness is precisely defined by the buried oxide of SOI wafer; (5) The stationary sensing electrodes anchored to the substrate also act as the limit stops to protect the accelerometer.