Role of H2O Molecules in Passivation Layer of a-InGaZnO Thin Film Transistors

Abstract

This letter analyzes performance and reliability of inverted staggered type amorphous indium-gallium-zinc oxide devices in a moist environment with H2O molecules in the passivation layer. There is a negative threshold voltage shift (Delta Vth) in the saturation region (V-D = 10 V), which increases with decreasing channel length. We propose that this is explained by the drain-induced barrier lowering that is due to the H2O molecules. Moreover, a hydrogen bonding model under bias stress is also proposed, in contrast to the conventional H2O doping model. Recovery behavior after bias stress and ac operation were utilized to distinguish the difference between these models.