Effects of Metal-Hydroxyl and InOx Defects on Performance of InGaZnO Thin-Film Transistor

The properties of metal-hydroxyl (M-OH) and InOx defects in InGaZnO (IGZO) and their influences on the performance of IGZO thin-film transistor (TFT) are investigated. The defects in the IGZO film are intentionally modulated by using various postmetallization-annealing (PMA) treatments. PMA is effective to densify the IGZO film and thus suppress the formation of M-OH. On the other hand, the PMA also leads to the formation of InOx near the edge of conduction channel. It is found that M-OH acts as deeplevel acceptor like trap and has a heavy influence on the off-current, threshold voltage, and subthreshold swing of the TFT. On the other hand, InOx acts as shallow-level donor andmainly affects the carriermobility of the TFT. The effects of M-OH and InOx on the TFT performance decrease and increase, respectively, with decreasing the channel length.