Role of Invisible Oxygen in the Trilayer Laminates of Ultrathin a-IGZO/SiO_x/a-IGZO Films

High Resolution Image Download MS PowerPoint Slide In this study, ultrathin multilayered films of IGZO/SiO x /a-IGZO were fabricated via radio frequency (RF) magnetron cosputtering, with the SiO x layer thickness systematically varied between 1 and 7 nm while maintaining a constant a-IGZO layer thickness. The effect of the SiO x thickness on the electrical properties of the films was thoroughly investigated. A significant deterioration in electrical performance was observed for SiO x layers up to 3 nm; however, an improvement was noted as the SiO x thickness increased to 7 nm. X-ray photoelectron spectroscopy (XPS) analysis revealed that the oxygen structure and chemical composition within the multilayers remained unchanged. However, it confirmed that the ultrathin 2 nm thick SiO x ( x ∼ 1.5) layer exhibited nonstoichiometric configurations. The contribution of Fowler–Nordheim (FN) tunneling was observed in multilayer films with varying thicknesses of SiO x . The presence of oxygen was found to play a critical role in modulating electron trap states within the SiO x layer, thereby mitigating the reduction in the charge carrier concentration in the films. By optimizing oxygen flow during deposition, we successfully eliminated the charge carrier drop in a-IGZO 20 nm /SiO x (2 nm) /a-IGZO 10 nm and a-IGZO 20 nm /SiO x (3 nm) /a-IGZO 10 nm films. Notably, the ultrathin SiO x layers in the a-IGZO/SiO x /a-IGZO films functioned as highly effective carrier suppressor layers, presenting a promising alternative to conventional doping approaches for controlling electrical performance.