A comparative study of amorphous InGaZnO thin-film transistors with HfOxNyand HfO₂gate dielectrics

High-κ HfO x N y and HfO 2 films are applied to amorphous InGaZnO ( a -IGZO) devices as gate dielectric using radio-frequency reactive sputtering. The electrical characteristics and reliability of a -IGZO metal–insulator–semiconductor (MIS) capacitors and thin-film transistors (TFTs) are then investigated. Experimental results indicate that the nitrogen incorporation into HfO 2 can effectively improve the interface quality and enhance the reliability of the devices. Electrical properties with an interface-state density of 5.2 × 10 11 eV −1 cm −2 , capacitance equivalent thickness of 1.65 nm, gate leakage current density of 3.4 × 10 −5 A cm −2 at V fb +1 V, equivalent permittivity of 23.6 and hysteresis voltage of 110 mV are obtained for an Al/HfO x N y / a -IGZO MIS capacitor. Superior performance of HfO x N y / a -IGZO TFTs has also been achieved with a low threshold voltage of 0.33 V, a high saturation mobility of 12.1 cm 2 V −1 s −1 and a large on–off current ratio up to 7 × 10 7 ( W / L = 500/20 µm) at 3 V.