Defect passivation and homogenization of amorphous oxide thin-film transistor by wet O2 annealing

Roles of H2O addition to an annealing atmosphere were investigated for amorphous In–Ga–Zn–O thin-film transistors fabricated at room temperature. Although dry O2 annealing improved saturation mobility (μsat) and subthreshold voltage swings (S), wet O2 annealing further improved them to μsat∼12cm2(Vs)−1 and S<0.12Vdecade−1 along with improvement of their uniformity. Desorption of OH-related species caused conductivity increase during thermal annealing at <310°C. Zn–O components started to desorb at ∼300°C for the unannealed and the dry O2 annealed films, while these were suppressed remarkably by the wet O2 annealing.