Improvements in passivation effect of amorphous InGaZnO thin film transistors

The performance of amorphous InGaZnO thin film transistors (a-IGZO TFTs) degrades apparently due to “passivation effect”, i.e. back-channel plasma damage from passivation layer deposition. In this letter two effective measures were taken to improve this effect. Double-stacked channel layer (DSCL), a novel active-layer structure, was proposed with which a-IGZO TFTs might suffer less plasma damage from passivation layer deposition, as was confirmed by investigation with high resolution transmission electron microscope (SRTEM). Moreover, two-stage annealing (TSA) method showed more advantages over conventional heat treatment at one fixed temperature in curing back-channel plasma damage caused by passivation deposition. The a-IGZO TFTs, Combined with these two improving methods, exhibited fine performance parameters (μFE of 2.0 cm2/V s, SS of 1.5 V/decade, Ion/Ioff of 106 and Vth of 1.5 V) as well as satisfactory ambient stability, meeting the requirements for their applications in flat panel displays.