Device instability of postannealed TiOx thin-film transistors under gate bias stresses

This paper investigates the negative bias instability (NBS) and positive bias instability (PBS) of titanium oxide (TiOx) thin-film transistors (TFTs) with different annealing temperatures. Structural analyses suggested that TiOx films annealed at 450 and 550 degrees C had average grain sizes of 200 and 400 nm, respectively. A TiOx TFT annealed at 550 degrees C exhibited respective threshold voltage (V-th) shifts of only -1.4 and 10.2V under NBS and PBS conditions. The origin of the instability was found to be a charge trapping mechanism caused by different grain sizes, boundaries, and changes in band edge states below the conduction band, which acted as electron and hole trap sites. (C) 2013 American Vacuum Society. [http://dx.doi.org/10.1116/1.4790572]