Investigating degradation behaviors induced by mobile Cu ions under high temperature negative bias stress in a-InGaZnO thin film transistors

Abstract

This letter investigates the effect of negative bias temperature stress (NBTS) on amorphous InGaZnO4 thin film transistors with copper electrodes. After 2000 s of NBTS, an abnormal subthreshold swing and on-current (Ion) degradation is observed. The recovery of the Id-Vg curve after either annealing or positive bias temperature stress suggests that there are some native mobile copper ions in the active layer. Both the existence of copper and the degradation mechanism can be confirmed by AC stress with different frequencies and by transmission electron microscope energy-dispersive X-ray spectroscopy analysis.