Improvements in the device characteristics of amorphous indium gallium zinc oxide thin-film transistors by Ar plasma treatment

The effect of Ar plasma treatment on amorphous indium gallium zinc oxide ($a$ -IGZO) thin films was investigated. The net electron carrier concentration $({10}^{20}–{10}^{21}{\mathrm{cm}}^{-3})$ of the $a$ -IGZO thin films dramatically increased upon their exposure to the Ar plasma compared to that $\left({10}^{14}{\mathrm{cm}}^{-3}\right)$ of the as-deposited thin film. The authors attempted to reduce the contact resistance between the $\mathrm{Pt}∕\mathrm{Ti}$ (source/drain electrode) and $a$ -IGZO (channel) by using the Ar plasma treatment. Without the treatment, the $a$ -IGZO thin film transistors (TFTs) with $W∕L=50∕4\mu \mathrm{m}$ exhibited a moderate field-effect mobility $\left({\mu }_{\mathrm{FE}}\right)$ of $3.3{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ , subthreshold gate swing $\left(\mathit{S}\right)$ of $0.25\mathrm{V}∕\text{decade}$ , and $I_{\text{on}∕\text{off}}$ ratio of $4\times {10}^7$ . The device performance of the $a$ -IGZO TFTs was significantly improved by the Ar plasma treatment. As a result, an excellent $\mathit{S}$ value of $0.19\mathrm{V}∕\text{decade}$ and high $I_{\text{on}∕\text{off}}$ ratio of $1\times {10}^8$ , as well as a high ${\mu }_{\mathrm{FE}}$ of $9.1{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ , were achieved for the treated $a$ -IGZO TFTs.