Characteristics of Amorphous In‐Ga‐Zn‐O Thin Films with Various Compositions Under Microwave Annealing

Abstract

In this study, the effects of microwave annealing (MWA) on the electrical properties of amorphous In‐Ga‐Zn‐O thin‐film transistors (a‐IGZO TFTs) are evaluated. To measure the transfer and output characteristics of as‐deposited, conventional thermal annealed (CTA), or microwave annealed TFTs, the devices are fabricated by varying the compositional ratios of IGZO films (In2O3:Ga2O3:ZnO = 1:1:1, 1:1:2, and 2:1:2 at%). The reliability is evaluated by measuring the threshold voltage shift under the gate bias stress and by analyzing the charge trapping characteristics according to the operating temperature. In addition, the interface trap density of the a‐IGZO channel/gate insulator and the volume density of the shallow trap of the channel layer are extracted to evaluate the difference in trap density according to the channel composition and the variation in the trap density as a result of the annealing process. Lastly, the sub‐gap density of states (DOS) of the TFTs is investigated to verify the compositional ratio and the annealing effect on the electrical characteristics and reliability of the devices. Based on these results, it is demonstrated that high‐performance a‐IGZO TFTs can be fabricated by using the low thermal budget MWA technique and by controlling the composition of the IGZO channel.