On-Chip Integration of ZnO Nanowires on Foundry Produced CMOS for Force Sensing

This work introduces a novel force sensor incorporating zinc oxide nanowires (ZnO NWs) synthesized via low temperature hydrothermal methods and integrated with foundry-produced CMOS at chip-scale. A floating gate transistor design has been fabricated with a titanium nitride (TiN) seed layer that enables the growth of the NWs. Encapsulated in Parylene-C, the ZnO NWs serve as the force-sensing material. Application of an external force induces a change in the polarization of these piezoelectric nanowires, resulting in a decrease in the FET channel current. This effect is attributed to the piezoelectric properties of the ZnO NWs and the Schottky contact with TiN. The device was characterized under a dynamic contact force range of 0.1–0.8 N, with drain and gate bias voltages of 0.5 V and 0.9 V, respectively. Within the linear region (0—0.4 N), it exhibits a sensitivity of 7.26 μA/N.