Pressure-dependent structural ordering of IGZO thin films by high-power pulsed magnetron sputtering

The influence of sputtering pressure on the structural and electrical properties of In–Ga–Zn–O (IGZO) thin films deposited by high-power pulsed magnetron sputtering (HPPMS) was systematically investigated. By controlling the deposition pressure between 0.65 and 3.0 Pa, the plasma characteristics during HPPMS deposition were significantly modified. Optical emission spectroscopy revealed that lower pressures increased the relative contribution of emissions from ionized species, suggesting enhanced plasma activity during film growth. Despite substrate temperatures remaining below 70 °C throughout deposition, X-ray diffraction analysis showed the emergence of structurally ordered and partially crystallized IGZO phases within an optimized pressure region around 1.5 Pa. X-ray photoelectron spectroscopy further demonstrated that the optimized growth condition promoted metal-oxygen bonding while reducing the higher-binding-energy O 1s component associated with oxygen-deficient bonding environments. Following post-deposition annealing, IGZO thin-film transistors fabricated from films deposited at 1.5 Pa exhibited the smallest subthreshold swing among all investigated conditions. These improvements are associated with enhanced structural ordering and reduced defect density resulting from pressure-controlled film growth. The present results demonstrate that sputtering pressure plays a critical role in governing the structural evolution of IGZO thin films during HPPMS deposition and provide further insight into pressure-controlled growth behavior under low-temperature deposition conditions.