Effect of double-layered Al2O3/SiO2 dielectric materials on In-Ga-Zn-O(IGZO)-based amorphous transparent thin film transistors

A double-layered Al2O3/SiO2 dielectric structure was applied to In-Ga-Zn-O-based amorphous thin film transistors through the atomic layer deposition (ALD) of aluminum oxide combined with thermally grown SiO2 dielectrics. The presence of ALD-based Al2O3 increased the on/off current ratio, decreased the sub-threshold slope, and decreased the threshold voltage. However, the addition of Al2O3 increased the turn-on voltage and slightly and adversely decreased the mobility. The device features appear to be associated with the presence of high-k Al2O3, which results in newly formed interfaces, oxide integrity, and high charge storage capabilities. The performance of the optimized thin film transistor is shown with the 50 nm Al2O3/50 nm SiO2 dielectric structure, which has a threshold voltage of 8.67 V, a turn-on voltage of 5.09 V, an on/off current ratio of 5.12×109 and a sub-threshold slope of 0.23 V/decade.