Improvement of Reliability in Low-Temperature Polycrystalline Silicon Thin-Film Transistors by Water Vapor Annealing

Abstract

Low-temperature polycrystalline silicon (poly-Si) thin film transistors (TFTs) are promising for realizing future displays such as a system-on-panel. Reliability is one of the most important issues for realizing system-on-panel. We performed water vapor annealing to improve reliability. To investigate the effect on the hot carrier effect, we imposed DC stress on a TFT with and without water vapor annealing. Degradation by the hot carrier effect was improved by the treatment. Analysis by emission microscope revealed that hot electron generation was enhanced by the treatment. To study the effect on thermal degradation, we also imposed DC stress on the TFT with and without the treatment. Degradation induced by Joule heating was also greatly improved. Analysis by thermal infrared imaging system revealed that operating temperature increased due to improved performance. We discussed the model for the treatment. Water vapor annealing improved the hot carrier effect and thermal degradation by reinforcing the Si–Si or Si–O bonding with activated oxygen.