The effect of a zinc–tin-oxide layer used as an etch-stopper layer on the bias stress stability of solution-processed indium–gallium–zinc-oxide thin-film transistors

摘要

We investigated the bias stress stability of solution-processed indium–gallium–zinc-oxide thin-film transistors (IGZO TFTs) using zinc–tin-oxide (ZTO) as the etch-stopper layer, the so-called dual-active-layered ZTO/IGZO TFT (DALZI TFT). The DALZI TFT can use a low-cost back-channel-etch structure because of the high chemical stability of the upper ZTO layer. The DALZI TFT exhibited only a threshold voltage shift of ?1.86V under negative bias illumination stress (NBIS) conditions (stress time = 1000 s), while the unpassivated IGZO TFT suffered from a threshold voltage shift of ?19.59V under NBIS conditions (stress time = 1000 s). The superior bias stress stability of the DALZI TFT is attributed not only to the densification effect by the multi-stacking process but also to the lower sensitivity to ambient gases (e.g., oxygen and water vapour) due to the low oxygen vacancy in the upper ZTO layer.