Double-Comb-Finger Design to Eliminate Cross-Axis Sensitivity in a Dual-Axis Accelerometer

We present a dual-axis accelerometer with zero cross-axis sensitivity. In general, multiaxis accelerometers with single proof-mass have multiple degrees of freedom, making them susceptible to high cross-axis sensitivity. In this article, a novel differential capacitive finger scheme is presented, which fully eliminates the in-plane cross-axis sensitivity at the device level. The proposed accelerometer is highly sensitive and has a differential capacitance scale factor of 80.97 fF/g (g = 9.8 m/s2) over + 10 g range with a pull-in voltage of 6 V. Additionally, the out-of-plane motion due to acceleration in the Z-axis direction is significantly suppressed due to the high-spring constant in that direction. The device is fabricated in a compact footprint of 1.6 mm x 1.6 mm using GlobalFoundries' Inertial Measurement Unit (IMU) platform.