Improved Performance of Scaled-Down α -InGaZnO Thin-Film Transistor by Ar Plasma Treatment

The origin of contact-resistance reduction induced by Ar plasma treatment and the effects of the treatment on the down-scaling of amorphous InGaZnO thin-film transistor are investigated. The treatment induces more TiOxand oxygen vacancies at the InGaZnO/Ti interface which facilitate electron flow between the InGaZnO film and source/drain (S/D) electrodes by trap-assisted tunneling, thus resulting in smaller width-normalized S/D contact resistance (RS/Dnorm= 19.9 Ω.cm) than that without Ar treatment (75.6 Ω.cm). Mainly owing to the reduction in RS/Dnorm, the Ar-treated device presents improved down-scaling behaviors than the untreated one. The Ar-treated device with a channel length of 5 μm still has good performance with a small sub-threshold swing of 252 mV/decade, a high field-effect mobility of 11.1 cm2/V.s, and a large ON-OFF current ratio of 1.7×107.