Performance Enhancement of InGaZnO Top-Gate Thin Film Transistor With Low-Temperature High-Pressure Fluorine Treatment

Abstract

In this work, the suppression of hydrogen diffusion in top-gate InGaZnO thin film transistors (TFTs) was observed. Under positive-bias temperature stress, the threshold voltage in short-channel devices was negatively shifted; this shift was attributed to hydrogen diffusion. To inhibit hydrogen migration, low-temperature high-pressure (LTHP) fluorine treatment was subsequently utilized. Under supercritical fluid states, fluorine, the most electronegative species of all elements, acted as a reactant and reduced mobile hydrogen. It was confirmed that the treatment benefited the characteristic properties of InGaZnO TFTs with varied channel lengths, especially in devices with short channels. The reliability of devices under stress improved through the LTHP treatment; the effects of suppression of hydrogen diffusion were illustrated by the energy band and capacitance–voltage curves of devices. Energy-dispersive X-ray spectroscopy of the specimen treated with LTHP indicated the presence of fluorine, which ensured the contribution of the treatment. Thus, LTHP treatment enables the realization of small-sized high-performance top-gate InGaZnO TFTs.