Enhancement of electrical stability of a-IGZO TFTs by improving the surface morphology and packing density of active channel

Abstract

a-IGZO films were deposited on Si substrates by d.c sputtering technique with various working power densities (p(d)) in the range of 0.74-2.22 W/cm(2). The correlation between material properties and their effects on electrical stability of a-IGZO thin-film transistor (TFTs) was studied as a function of p(d). At a p(d) of 1.72 W/cm(2) a-IGZO film had smoothest surface roughness (0.309 nm) with In-rich and Ga-poor cation compositions as a channel. This structurally ordered TFTs exhibited a high field effect mobility of 9.14 cm(2)/Vs, a sub-threshold swing (S.S.) of 0.566 V/dec, and an on-off ratio of 10(7). Additionally, the V-th shift in hysteresis loop is almost eliminated. It was shown that the densification of the a-IGZO film resulted in the reduction of its interface trap density (1.83 x 10(12) cm(-2)), which contributes for the improvement in the electrical and thermal stability. (C) 2012 Elsevier B.V. All rights reserved.