Highly reliable photosensitive organic-inorganic hybrid passivation layers for a-InGaZnO thin-film transistors

We report the fabrication of a photosensitive hybrid passivation material on amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) that greatly enhance its stability and improve its electrical characteristics. The hybrid passivation based on polysilsesquioxane is transparent and fabricated using a simple solution process. Because the passivation is photosensitive, dry etching was never performed during TFT fabrication. TFTs passivated with this material had a small threshold voltage shift of 0.5V during positive bias stress, 0.5V during negative bias stress, and -2.5V during negative bias illumination stress. Furthermore, TFTs passivated by this layer were stable after being subjected to high relative humidity stress-confirming the superb barrier ability of the passivation. Analysis of secondary ion mass spectrometry showed that a large amount of hydrogen, carbon, and fluorine can be found in the channel region. We show that both hydrogen and fluorine reduced oxygen vacancies and that fluorine stabilized weak oxygen and hydroxide bonds. These results demonstrate the large potential of photosensitive hybrid passivation layers as effective passivation materials. (C) 2015 AIP Publishing LLC.