Etching Characteristics and Changes in Surface Properties of IGZO Thin Films by O2 Addition in CF4/Ar Plasma

Abstract

Plasma etching processes for multi-atomic oxide thin films have become increasingly important owing to the excellent material properties of such thin films, which can potentially be employed in next-generation displays. To fabricate high-performance and reproducible devices, the etching mechanism and surface properties must be understood. In this study, we investigated the etching characteristics and changes in the surface properties of InGaZnO4 (IGZO) thin films with the addition of O2 gases based on a CF4/Ar high-density-plasma system. A maximum etch rate of 32.7 nm/min for an IGZO thin film was achieved at an O2/CF4/Ar (=20:25:75 sccm) ratio. The etching mechanism was interpreted in detail through plasma analysis via optical emission spectroscopy and surface analysis via X-ray photoelectron microscopy. To determine the performance variation according to the alteration in the surface composition of the IGZO thin films, we investigated the changes in the work function, surface energy, and surface roughness through ultraviolet photoelectron spectroscopy, contact angle measurement, and atomic force microscopy, respectively. After the plasma etching process, the change in work function was up to 280 meV, the thin film surface became slightly hydrophilic, and the surface roughness slightly decreased. This work suggests that plasma etching causes various changes in thin-film surfaces, which affects device performance.