Effective Improvements in Microstructure and Electrical Properties of the IGZO Films by Sputtering Angles

Indium gallium zinc oxide (IGZO)/poly(ethylene terephthalate) (PET) specimens were prepared under inclination angles of 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees. The film thickness, top and lateral surface morphologies, and chemical compositions were investigated by X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (Ga2p, Ga3d, In3d, Zn2p, and O1s). The intensity ratio (IR) is defined as the ratio of the InGaO3(ZnO)(3) peak value to the sum of the peak values of InGaO3(ZnO)(3) and InGaZnO4. Decompositions of O1s and Ga3d provide the Gaussian-like profiles of Ga-Ga, In4d, Ga-O, O-1, O-2, and O-3. The ratio of the O-2 peak intensity (PI) to the sum of the O-1 and O-2 intensities, termed IRO2, was used as an indicator of oxygen-vacancy defects in the five specimens. An increase in the inclination angle significantly reduced surface roughness. An increase in IRO2, due to inclination angle increase, elevated the carrier concentration, which is consistent with the increases in O-2 PI often being advantageous for carrier mobility reductions. Moreover, a high IRO2 value is unfavorable for increasing film's adhesive strength to the PET substrate.