Investigating Effect of Postannealing Time on Positive Bias Stress Stability of In–Ga–Zn–O TFT by Conductance Method

The conductance method was used to investigate the positive bias stress (PBS) degradation mechanism of In-Ga-Zn-O (IGZO) thin-film transistor (TFT). The effects of postannealing time on the PBS degradation mechanism were investigated. The stabilization of the donorlike interface defects was found to be the reason for the threshold voltage instability in the IGZO-TFT under the PBS test. The donorlike defects at the front channel interface and in the plasma-enhanced chemical vapor deposition (PE-CVD) SiOx acted as the electron trapping centers. The electron trapping resistance of the PE-CVD SiOx was improved by increasing the postannealing time, resulting in an improvement in the PBS stability. However, long-time postannealing-induced creation of the deep acceptorlike interface defects in the TFT under the PBS. The energy distribution of the created deep acceptorlike interface defects was revealed using the conductance measurement.