Proposals on Lower Thermal Budget Process for In-Ga-Zn-O Thin Film Transistor Using HfO2 Gate Insulators Prepared by Atomic-Layer Deposition at a Temperature of 150°C

The device characteristics and reliability of the In-Ga-Zn-O (IGZO) TFTs employing the HfO2 gate insulator prepared by atomic-layer deposition (ALD) at a temperature as low as 150°C were investigated. The leakage current density and the dielectric constant for this HfO2 thin film were obtained to be 3.8×10−7 A/cm2 and 22, respectively. The IGZO TFT showed a saturation mobility of 6.8 cm2/Vs and a subthreshold swing of 0.26 V/dec. Under the positive bias stress condition, the threshold voltage shift was evaluated to be less than −0.19 V.