High performance thin film transistors with cosputtered amorphous indium gallium zinc oxide channel

Abstract

The authors report the fabrication of high performance thin film transistors (TFTs) with an amorphous indium gallium zinc oxide $\left(a\text{-}\mathrm{IGZO}\right)$ channel, which was deposited by cosputtering using a dual IGZO and indium zinc oxide (IZO) target. The effect of the indium content on the device performance of the $a\text{-}\mathrm{IGZO}$ TFTs was investigated. At a relatively low IZO power of $400\mathrm{W}$ , the field-effect mobility $\left({\mu }_{\mathrm{FE}}\right)$ and subthreshold gate swing (S) of the $a\text{-}\mathrm{IGZO}$ TFTs were dramatically improved to $19.3{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ and $0.35\mathrm{V}$ /decade, respectively, compared to those ($11.2{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ and $1.11\mathrm{V}$ /decade) for the TFTs with the $a\text{-}\mathrm{IGZO}$ channel (reference sample) prepared using only the IGZO target. The enhancement in the subthreshold $I_{\mathrm{DS}}\text{-}{V}_{\mathrm{GS}}$ characteristics at an IZO power of $400\mathrm{W}$ compared to those of the reference sample was attributed to the reduction of the interface trap density rather than the reduction of the bulk defects of the $a\text{-}\mathrm{IGZO}$ channel.