AC Bias-Temperature Stability of a-InGaZnO Thin-Film Transistors With Metal Source/Drain Recessed Electrodes

In this paper, we fabricated metal source/drain recessed nearly self-aligned amorphous indium-gallium-zinc-oxide thin-film transistors (TFTs) that are highly stable under ac bias-temperature stress (BTS). For TFTs of the size W/L=60 μm/10 μm, the stress-induced threshold voltage shifts are all within -0.35 V. A comprehensive investigation of ac BTS stress polarity, frame time, and duty cycle dependence is presented in the context of high-resolution high-refresh rate active-matrix flat-panel displays. We find that higher frequency bipolar ac pulses increase the device instability. The threshold voltage instability may be reduced significantly by decreasing the duty cycle of the stress waveform.