Improvement of Negative Bias Temperature Illumination Stability of Amorphous IGZO Thin-Film Transistors byWater Vapor-Assisted High-Pressure Oxygen Annealing

Abstract

The effect of high-pressure annealing on the performance and negative bias temperature illumination stress (NBTIS)-induced instability of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) is investigated. IGZO TFTs that were annealed in a H2O vapor-assisted high-pressure O-2 atmosphere exhibited significantly improved field-effect mobility and stability against NBTIS compared with those annealed in only high-pressure O-2 or air. Annealing under high-pressure O-2 in the presence of H2O vapor effectively reduces oxygen-related defects, which act as subgap states within the bandgap. This phenomenon affects band alignments, including the bandgap and conduction band offset [Delta(E-C-E-F)] of IGZO semiconductors, and is the basis for the improved performance and stability of the TFTs.