Selective metallization of amorphous-indium-gallium-zinc-oxide thin-film transistor by using helium plasma treatment

In this study, the effects of helium (He) plasma treatment on amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) have been investigated. The He plasma treatment induced a dramatic decrease of the resistivity in a-IGZO thin films from 1.25 x 10(6) to 5.93 m Omega cm. After 5 min He plasma treatment, the a-IGZO films showed an increase in carrier concentration to 6.70 x 10(19) cm(-3) combined with a high hall mobility of 15.7 cm(2) V-1 s(-1). The conductivity improvement was linked to the formation of oxygen vacancies during the He plasma treatment, which was observed by x-ray photoelectron spectroscopy analysis. The a-IGZO films did not appear to be damaged on the surface following the plasma treatment and showed a high transmittance of about 88.3% at a wavelength of 550 nm. The He plasma-treated a-IGZO films were used as source/drain (S/D) electrodes in a-IGZO TFTs. The devices demonstrated promising characteristics, on pair with TFTs using Al electrodes, with a threshold voltage (V-T) of -1.97 V, sub-threshold slope (SS) of 0.52 V/decade, saturation mobility (mu(sat)) of 8.75 cm(2) V-1 s(-1), and on/off current ratio (I-on/I-off) of 2.66 x 10(8).