Optimizing Oxygen Plasma Treatment Time to Improve the Characteristics of a-IGZO Thin-Film Transistors and Resistive-Load Inverters

Amorphous indium–gallium–zinc oxide (a-IGZO) is a widely studied semiconductor for cutting-edge electronics applications because of its low absorbance, high charge carrier mobility, and versatility. For the practical application of a-IGZO thin films, postdeposition thermal treatment is typically applied to enhance the device’s performance. Here, we present a study on the effect of oxygen plasma posttreatment of thermally annealed, sputter-deposited a-IGZO thin films to determine the optimal treatment time using a helical plasma source. The performance of devices with a-IGZO active layers exposed to oxygen plasma for different durations is compared, and the stability under constant bias is evaluated. It is found that temporarily exposing the film surface to high-energy oxygen species can improve the charge transport properties, resulting in superior device performance such as more than tenfold increase in the ON–OFF ratio, a nearly doubling of charge carrier mobility and improved bias stress stability. However, under prolonged exposure, the device deteriorates, indicating the importance of properly designing and optimizing the fabrication processes of oxide semiconductor devices. To demonstrate the practical applicability of the transistors with optimized a-IGZO active layers, load-type inverters are prepared, and their performance is evaluated and compared quantitatively to that of a device with a pristine a-IGZO active layer.