High-Performance Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors With $\hbox {HfO}_{x}\hbox {N}_{y}/\hbox {HfO}_{2}/\hbox {HfO}_{x}\hbox {N}_{y}$ Tristack Gate

We have fabricated and investigated amorphous indium gallium zinc oxide (α-IGZO) thin-film transistors (TFTs) by using HfO_xN_y/HfO₂/HfO_xN_y (NON) as the gate dielectric. The NON tristack dielectric structure can increase the gate capacitance density, effectively improve interface properties of both the gate/dielectric and dielectric/active channels, suppress the charge trap density, and reduce the gate leakage. The α-IGZO TFT (W/L = 200/10 μm) with NON shows superior performance such as a saturation current of 0.33 mA, an ON/OFF-current ratio of 2.2 × 10⁶, a saturation mobility of 10.2 cm²/V · s, a source/contact resistivity of 83 Ω · cm, a subthreshold swing of 0.13 V/dec, and enhanced stressing reliability.