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 H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O molecules in the passivation layer. There is a negative threshold voltage shift (Δ Vth) in the saturation region (VD = 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 H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O molecules. Moreover, a hydrogen bonding model under bias stress is also proposed, in contrast to the conventional H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O doping model. Recovery behavior after bias stress and ac operation were utilized to distinguish the difference between these models.