Quad-seesaw-electrode type 3-axis tactile sensor with low nonlinearities and low cross-axis sensitivities

This paper reports a microelectromechanical systems (MEMS) tactile sensor with a quad-seesaw-electrode (QSE) structure, which allows integration with a CMOS substrate. The QSE structure enables fully-differential detection and 3-axis force detection by utilizing the difference of the working mode of the four seesaw electrodes. In this study, we designed the sensor structure for upgrading of the 3-axis characteristics by improvement of the nonlinearities and miniaturization with sufficient sensitivities. Simulations by the finite element method (FEM) and capacitance calculations confirmed the 3-axis output characteristics, as well as the working principle. Then, a 3.0-mm-square sensor chip with the QSE structure was fabricated with a silicon-on-insulator (SOI) substrate and an anodically bondable low-temperature co-fired ceramics (LTCC) substrate as an alternative to the CMOS substrate. The measurement results successfully demonstrated the 3-axis fully-differential detections with principal-axis sensitivities over 20 fF/N, nonlinearities of almost 1% with 1 N full scale, and cross-axis sensitivities within 10%.