Effect of Deposition Temperature of SiOx Passivation Layer on the Electrical Performance of a-IGZO TFTs

We investigated the effect of the deposition temperature on the electrical performance of SiOx passivation layers for amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs). Compared to the time-of-flight secondary ion mass spectroscopy depth profile of the IGZO film with a SiOx passivation layer deposited at low temperature (150oC ), that with the SiOx film formed at 300oC exhibited the significant migration of metal ions from the IGZO film into the SiOx passivation layer. These results were attributed to the high-energy ion bombardment on the IGZO channel layer. In order to suppress the interdiffusion of In, Ga, and Zn atoms between the IGZO and passivation layers, we proposed double SiOx passivation using different substrate temperatures. It combines the merits of low-temperature (150oC) and high-temperature (300oC) passivations and compensates for their individual weaknesses. We confirmed the enhanced electrical characteristics and improved reliability of the IGZO TFTs compared to those of the conventional device.