Flexible Tactile Sensors Using AlN and MOSFETs Based Ultra-Thin Chips

This paper presents ultrathin chips (UTCs) based flexible tactile sensing system for dynamic contact pressure measurement. The device comprises of an AlN piezocapacitor based UTCs tightly coupled with another UTCs having metal-oxide-semiconductor field-effect transistors (MOSFETs). In this arrangement the AlN piezocapacitor forms the extended gate of MOSFETs. Both AlN piezocapacitor and MOSFET based UTCs are obtained by post-process reduction of wafer thicknesses to ~<inline-formula> <tex-math notation="LaTeX">$35\mu \text{m}$ </tex-math></inline-formula> using backside lapping. The performances of both UTCs were evaluated both before and after thinning and there was no noticeable performance degradation. The UTC-based AlN piezocapacitor exhibited six times higher sensitivity (43.79mV/N) than the thin film-based AlN sensors. When coupled with MOSFETs based UTC, the observed sensitivity was 0.43N−1. The excellent performance, flexible form factor and compactness shows the potential of presented device in applications such minimal invasive surgical instruments where high-resolution tactile feedback is much needed.