Comprehensive studies of the degradation mechanism in amorphous InGaZnO transistors by the negative bias illumination stress

Abstract

In this paper an examination is presented of the effect of the gate dielectric materials and bilayer stack on the negative bias illumination stress (NBIS) instability of InGaZnO (IGZO) TFTs. The threshold voltage ( V th) movement by NBIS was greatly dependent on the valence band off-set and the effective vertical electrical field, suggesting that the trapping or injection of photo-generated hole carriers into the gate insulator plays an important role. The process of hole carrier creation by photon irradiation onto the IGZO channel layer is shown by independent experiments to involve the oxygen vacancy defects. The reduction in the oxygen vacancy of IGZO semiconductor by the high pressure O 2 annealing resulted in the strong increase in the V th instability induced by NBIS, indicating that the generation of hole carriers can result from the photo-induced transition mechanism from [ V O] to [ V O 2 + ].