| Abstract: | Polysilicon Thin Film Transistors (TFT's), fabricated at temperature lower than 600°C, are now largely used in many applications, particularly in large area electronics. The reliability of these TFT's under different electrical conditions is then questionable. In this work, Gate bias stress is studied in two types of polysilicon TFT's originated from the same process. One type is unhydrogenated and the other is submitted to a Radio-Frequency hydrogen plasma. As this hydrogenation step is known to improve the TFT's performances but to introduce unstability, the unhydrogenated TFT's are expected to be more stable. The behaviours of the two types of TFT's under the gate bias stress are found however only different. The bias aging of unhydrogenated TFT's fit with the known model of the n-channel c-Si MOSFET's bias stress. The behaviour of the hydrogenated TFT's is explained from the model of defect creation in hydrogenated amorphous silicon. |
