Fabrication of indium gallium zinc oxide (IGZO) TFTs using a solution-based process

Highly transparent (90% in the visible region) indium gallium zinc oxide (IGZO) thin films were deposited using a spin coating process with a newly developed precursor solution. Acetonitrile was used as the solvent in the preparation of the metal halide precursor solution for the deposition of the IGZO thin films. Ethylene glycol was added to the solvent at four different volume ratios of acetonitrile to ethylene glycol to complement the chemical properties of acetonitrile in order to avoid the de-wetting phenomenon during the deposition process. The IGZO thin films were prepared at a stoichiometric molar ratio of 2:2:1 on the basis of the theoretical In2O3-Ga2O3-ZnO structure. The IGZO metal-oxide-semiconductor field-effect transistor (MOSFET), with a field-effect mobility (FE) as high as 1.1cm2/V s, a turn on voltage of 15.8V, and a current on-to-off ratio greater than 107, was successfully fabricated in this study. This low cost solution-based deposition process was applicable for the fabrication of transparent conducting oxide (TCO)-based devices.