Effect of target composition control on the properties of IGZO thin films

Abstract

Unlike previous approaches that relied on tailoring sputtering processes to control film properties, in this study, powder metallurgy techniques were employed to fabricate four IGZO ceramic targets with distinct molar ratios (In₂O₃:Ga₂O₃:ZnO = 1:1:1, 1:1:2, 1:1:4, and 1:1:8, hereafter denoted as IGZO-111, IGZO-112, IGZO-114, and IGZO-118, respectively). The influence of target microstructure on the microstructure and optoelectronic properties of IGZO thin films deposited by magnetron sputtering was systematically investigated. Both the target and the resulting thin films were comprehensively characterized using multiple analytical techniques. The results indicate that the phase composition of the IGZO target (corresponding to In₂Ga₂ZnO₇, InGaZnO₄, InGaZn₂O₅, and InGaZn₄O₇) at different ratios significantly affects the deposition rate, crystalline state, surface morphology, optical bandgap, and electrical properties of the resulting thin films. With increasing Zn content in the target, the film deposition rate rises from 7.22 nm/min (IGZO-111) to 11.79 nm/min (IGZO-118), the optical bandgap decreases from 3.57 to 3.20 eV, and the resistivity increases from 3.91 × 10⁻¹ to 2.50 × 10² Ω cm. Films deposited using the IGZO-112 target exhibit optimal uniformity and density, featuring the lowest root-mean-square surface roughness (1.64 nm) and an average visible light transmittance of 89.34%. This study reveals the critical role of target composition and structural adjustment in optimizing the performance of IGZO thin films, providing essential guidance for material design in high-performance transparent oxide electronic devices.