Effect of Two-Step Annealing on High Stability of a-IGZO Thin-Film Transistor

In this article, the effects of two-step annealing at the active layer (AL) and the completed device on the electrical properties and stability of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) are studied. The subthreshold swing (SS) and stability of a-IGZO TFT devices are greatly improved, and the hump phenomenon under the negative bias illumination stability (NIBS) is particularly well suppressed when the TFT devices are treated with an optimum two-step annealing process (200 °C of preannealing and 300 °C of postannealing). Based on the analysis of the surface morphology, internal chemical state, and electrical properties of the IGZO thin film, an improvement of two-step annealing devices may be due to hydrogen filling the oxygen vacancies in the AL and well passivating the defects between insulating layer and AL. The result illustrates that two-step annealing is a promising method for IGZO TFT, which is not only beneficial to improve the stability of the device but also suppresses the hump phenomenon in NIBS.