Twin Thin-Film Transistor Nonvolatile Memory With an Indium–Gallium–Zinc–Oxide Floating Gate

A polycrystalline silicon (poly-Si) channel twin thin-film transistor (twin-TFT) nonvolatile memory (NVM) device with In-Ga-Zn-O
x
(IGZO) as a storage layer is demonstrated. IGZO-FG twin-TFT NVM exhibits a large memory window Δ
V
_th
. A
V
_CG
at 18 V for 10 ms can achieve 5.6 V of Δ
V
_th
. An extrapolation of the memory window to ten years demonstrates that the stored charge still remains 65% of its initial value. Coupling ratio effect and gate length effect are discussed in detail. Such a low-temperature IGZO-FG twin-TFT NVM device is feasible for integration in IGZO-based display circuits for system-on-panel applications.