An SOI 3-axis accelerometer with a zigzag-shaped Z-electrode for differential detection

We have developed a fully-differential 3-axis accelerometer with a novel zigzag-shaped Z-electrode, which is used for motion controls of automobiles and robots. The zigzag-shaped electrode is composed of two capacitors which detect differential change in capacitance. The gaps of the zigzag-shaped electrode are precisely equal due to use of the same oxide layer of an SOI wafer. Therefore, the zigzag-shaped Z-electrode, which we invented in 2004, can improve the precision of differential detection of the Z-electrode. We designed a fully differential 3-axis accelerometer with the zigzag-shaped Z-electrode structure. The experimental results of a prototype chip showed good performance with low cross-axis sensitivity and non-linearity; cross-axis sensitivity of the Z-axis outputs before the differential amplification as small as 1.4 % FS (FS = +/-1.5g), non-linearity of 0.4% FS.