Amorphous Silicon Thin-Film Transistors Employing Photoprocessed Tantalum Oxide Films as Gate Insulators

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Abstract
Amorphous silicon thin-film transistors (a-Si:H TFT's) with photoprocessed TaO x /photo-CVD SiN x double layer gate insulator have been fabricated. The usefulness of photoprocessed TaO x film as a gate insulator and the reason for improvement in TFT characteristics thereby are discussed. There is a correlation among TFT characteristics, a-Si:H/SiN x interface properties and stress in the gate insulator. Better TFT characteristics are obtained for higher compressive stress in the gate insulator due to better interface properties. The photoprocessed TaO x film plays a role in changing the stress and consequently improves TFT characteristics. Annealing of TaO x film in the presence of both UV irradiation and an oxygen ambient after photo-CVD deposition also improves the stability of TFT characteristics.