Monolithic/Vertical Integration of Piezo-Resistive Tactile Sensor and Inductive Proximity Sensor Using CMOS-MEMS Technology

This study demonstrates the monolithic/vertical integration of piezo-resistive tactile and inductive proximity sensing units using standard TSMC CMOS process (Fig. 1). Before contact, the proximity sensing of object is achieved by inductance change of spiral coil; after contact, the tactile load from object is detected by resistance change of bent piezo-resistors (Fig. 1b). The proposed sensor design to offer the proximity/tactile sensing capabilities has four merits: (1) tactile and proximity sensing units can be vertically implemented and integrated on one chip, (2) no interference between two sensing mechanisms to enable sensing units working independently, (3) simultaneous detection for proximity/tactile is achieved to enable continuous object monitoring before/after contact, (4) footprint reduction of sensing chip due to vertical-integrated design. Measurements indicate the sensitivity of tactile unit is 0.73mV/N (loading range: 0-2N), sensing distance of proximity unit is 2.5mm for stainless steel object, and simultaneous/continuous detection for tactile and proximity are also demonstrated.