3-Axis fully-integrated surface-mountable differential capacitive tactile sensor by CMOS flip-bonding

This paper reports a 3-axis MEMS-CMOS integrated tactile sensor for surface-mounting on a flexible bus line. This 3-axis sensor uses a bran-new CMOS LSI with capacitive sensing circuit and other extended functionalities (e.g. configurability and a robust clock data recovery algorithm). The sensor is composed of a flip-bonded CMOS substrate with a sensing diaphragm and a special low temperature co-fired ceramics (LTCC) substrate with vias. These substrates are electrically and mechanically connected by Au-Au bonding, forming sealed differential capacitive gaps. The completed sensor outputs coded 3-axis digital signals according to applied 3-axis force with small cross-sensitivity and hysteresis.