Investigations on the Negative Shift of the Threshold Voltage of Polycrystalline Silicon Thin-Film Transistors Under Positive Gate Bias Stress

Different from the conventional degradation phenomenon under positive bias stress (PBS), the shift of the transfer characteristic curve of polycrystalline silicon thin-film transistors (TFTs) to the negative gate bias direction after PBS is observed and reported. The PBS degradation is found to be recoverable and the recovery proceeds at a faster rate first and then continues at a much slower rate. The recovery can be further accelerated at a higher temperature or by applying a negative gate bias. After detailed data analysis, the degradation mechanism is proposed to be the generation of protons in the gate oxide and its accumulation at the channel/gate oxide interface. The proposed degradation model could explain both the degradation phenomena and the recovery behaviors of PBS degradation.

Automated summary

Research has shown that under positive bias stress (PBS), the transfer characteristic curve of polycrystalline silicon thin-film transistors (TFTs) shifts towards the negative gate bias direction, with a recoverable degradation process that initially proceeds at a fast rate before slowing down. Further acceleration of recovery can be achieved at higher temperatures or by applying a negative gate bias. The proposed degradation mechanism involves the generation of protons in the gate oxide and their accumulation at the channel/gate oxide interface.