Abstract
This study extends the concepts in previous works to present an inductive-force/capacitive-proximity tactile sensor consisting of four-layer stacked interdigitated spiral-coils chip with vertically integrated stainless steel/Cr steel bumps using flip-chip bonding technology. The chip is implemented using the TSMC 0.18 μm 1P6M standard CMOS process. Key features of this work include: (1) Flip-chip bonding for vertical integration of interdigitated spiral-coils chip with stainless steel and Cr steel bumps; (2) Stainless steel bump for magnetic flux concentration to enhance the inductive force sensing; (3) Stainless steel bump for lowering parasitic capacitance to improve the capacitive proximity sensing. The integrated stainless steel with 2-turn coils enhances force sensing signal to 300.5 nH/N under a 1 N loading (about 47% improvement) and demonstrates the feasibility of stabilizing the capacitive proximity sensing signal.