Analysis of channel length-dependent degradation of IGZO TFTs under positive bias stress through TCAD simulation

This paper investigated the degradation mechanism of InGaZnO (IGZO) thin-film transistors (TFTs) that depend on channel length under positive bias stress (PBS). Although the further degradation of short-channel IGZO TFTs has been previously reported, it has yet to be fully understood. Using technology computer-aided design (TCAD) simulations, we found that the primary mechanism of the channel length-dependent degradation is the additional electron trapping at channel edges where electrons are diffused from the <i>n</i>⁺ region. We also observed that the degradation was minimized when the <i>n</i>⁺ region had a relatively low carrier concentration. Based on these findings, we demonstrated a lightly doped drain-integrated oxide TFT and repositioned the source/drain electrodes. The TCAD simulation results verified that the proposed structure could prevent PBS-induced degradation in a short channel without compromising the drain’s current performance.