High Performance and Stable Flexible Memory Thin-Film Transistors Using In-Ga-Zn-O Channel and ZnO Charge-Trap Layers on Poly(Ethylene Naphthalate) Substrate

A flexible charge-trap-type memory (f-CTM) thin-film transistor was proposed and fabricated on poly(ethylene naphthalate) (PEN) substrate. All the fabrication process temperature was suppressed below 180 °C. To improve the surface roughness and water vapor transmission rate of the PEN substrate, the organic/inorganic hybrid barrier layer was introduced. The gate-stack was composed of all oxide layers, such as In-Ga-Zn-O active channel, ZnO charge-trap layer, Al₂O₃ blocking/tunneling layers, and In-Sn-O transparent electrode, in which double-layered tunneling and top-protection layers were designed, so that the f-CTMs could exhibit stable and excellent device performance. As results, wide memory margin (25.6 V), fast programming speed ( ∼ 500 ns), and long retention time (>3 h) were obtained at room temperature and at 80 °C. Furthermore, these memory device characteristics were not degraded even after the delamination of PEN substrate and under the bending situation with a given curvature radius (3.3 mm).