Fabrication and Characterization of Film Profile Engineered ZnO TFTs With Discrete Gates

Abstract

By virtue of the film-profile engineering scheme and properly designed device structure, ZnO TFTs with discrete bottom gates and sub-micron channels were fabricated and characterized. In the fabrication, a suspended bridge constructed over the bottom gate is used to tailor the profile of subsequently deposited films. Superior electrical characteristics in terms of ultrahigh ON/OFF current ratio (∼10 10 ), steep sub-threshold swing (66∼108 mV/dec), and very low off-state leakage current are demonstrated with the fabricated devices. Effects of channel lengths on the device characteristics are also explored. Because of more effective shadowing of the depositing species with a longer suspended bridge, the deposited films become thinner at the central channel. As a result, the device shows more positive turn-on voltage and better subthreshold swing with increasing channel length.INDEX TERMS Metal oxide, film profile engineering (FPE), ZnO, thin-film transistor.