Investigation of Hydrogen Diffusion in Top Gate IGZO TFTs by Using Various Pulse-Width Operation Method and Capacitance-Voltage Analysis

During high current stress condition in IGZO TFTs, self-heating effect occurs and hydrogen diffusion will cause electrical degradation in I-V curves. Through direct current mode and different pulse-width mode voltage operating conditions, it is found that IGZO TFTs have different degradation trend. During high current stress, stronger electric field and thermal field will both affect the degradation in I-V curves. To exclude the impact of thermal field, the high current stress is conducted at low temperature environment. Therefore, we can determine that the thermal field is the main cause of hydrogen diffusion, which leads the threshold voltage left shift in I-V curves and the occurrence of C-V humps. In addition, through the C-V analysis, the progress of hydrogen diffusion is further investigated.