A Differential Capacitive Three-Axis SOI Accelerometer using Vertical Comb Electrodes

This paper reports a differentially detecting capacitive three-axis SOI accelerometer using novel vertical comb electrodes. The accelerometer structure was fabricated by surface-micromachining technique and consists of only the device layer of a SOI wafer without lower or upper electrodes. The bottom faces of both movable and fixed electrodes are in the same plane at their initial positions but those heights are different. It is also an important feature that the device applies fully differential detections in all three-axis by using only two pairs of four type capacitors. As an initial result, the capacitance changes against three-axis acceleration were observed. The capacitance sensitivities to X and Z-axis acceleration against Y-axis rotation were 1.04 fF/G and 1.14 fF/G, respectively.