Gate Bias Stress-Induced Threshold Voltage Shift Effect of a-IGZO TFTs with Cu Gate

The gate bias stress-induced threshold voltage shift effect of amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) with Cu gate is investigated in this brief. It is revealed that the Cu-gated TFTs with SiOx gate insulator suffer from serious electrical performance degradation under gate bias stress owing to Cu diffusion into the gate insulator and channel region. A stacked gate insulator of SiOx/SiNx is then proposed to suppress the Cu diffusion. Experimental results show that the Cu-gated TFTs with the stacked gate insulators have a comparable threshold voltage shift effect with that of the conventional TFTs with Mo electrode and SiOx insulator, under both positive and negative gate bias stresses.