Integrated 3-axis tactile sensor using quad-seesaw-electrode structure on platform LSI with through silicon vias

This paper reports a MEMS-on-LSI integrated tactile sensor for robot applications that has both fully differential capacitive 3-axis force sensing and signal processing in a single chip. The MEMS part is composed of a quad-seesaw-electrode structure that senses 3-axis force with fully differential capacitive detection. The LSI part is an original sensor platform LSI that enables signal processing and serial bus communication for various types of sensors. The sensor platform LSI was processed for the MEMS-on-LSI integration after fabrication in a semiconductor foundry; the additional processing formed 300-μm-deep annular-type through silicon vias (TSVs), a bonding ring, and sensor electrodes. By Au-Au thermocompression bonding of the fabricated MEMS and LSI parts, a 2.8-mm-square surface-mountable MEMS-on-LSI integrated tactile sensor was completed. A working test demonstrated that digital packet transmission through TSV and confirmed the working principle of 3-axis force sensing with fully differential capacitive detection. A fully integrated and fully differential 3-axis tactile sensor was achieved on a single chip.