Julia Okvath

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Indium-gallium-zinc oxide (IGZO) thin-film transis-tors (TFTs) used in LCD display technologies exhibit significant instability when exposed to thermal stress above 100◦C. Bottom-gate TFTs subjected to prolonged heat treatment at 140◦C experience a voltage shift of 2 V over 120 minutes. Double-gate TFTs experience an even more pronounced shift of 7 V over 120 minutes. This instability is believed to be associated with water molecules incorporated in the PECVD TEOS SiO2 passivation layer, with an enhanced response in the double-gate device due to the liberation of monatomic hydrogen from the reaction of water with the top-gate metal. This research investigates the effectiveness of atomic-layer deposited Al2O3 and HfO2 films as capping materials for IGZO TFTs. After being exposed to thermal stress at 140◦C, capped devices demonstrate a significant improvement, with minimal variation in electrical characteristics.

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