Effect of sputtering working pressure on the reliability and performance of amorphous indium gallium zinc oxide thin film transistors

Abstract

In this study, the reliability and electrical properties of indium gallium zinc oxide (IGZO) thin film transistors (TFTs) are investigated when the working pressure of the sputtering system is varied. As IGZO is deposited at a low working pressure, the sputtering yield increases and the film density increases from 5.84 to 6.00 g/cm3 based on x-ray reflectivity measurements. IGZO TFT sputtered at low working pressure has a mobility of 8.05 cm2/V s, a threshold voltage of 1.25 V, and a subthreshold swing of 0.25 V/dec. In addition, x-ray photoelectron spectroscopy analysis shows that the oxygen content in the film decreases when IGZO is deposited at a low working pressure, resulting in improved positive bias stress reliability due to the oxygen-poor film. Furthermore, the IGZO film deposited at a low working pressure effectively prevents the formation of defects caused by the environment such as H2O molecules.