BCl3/Ar plasma etching for the performance enhancement of Al-doped ZnO thin films

Abstract

Al-doped ZnO (AZO) has attracted significant attention as a transparent electrode with low cost, high transmittance, high electrical conductivity, and excellent mechanical flexibility. A high-resolution patterning process is required for its application to next-generation displays, which can be achieved through the plasma etching process. In this study, we investigated the etching mechanism for Al-doped ZnO thin films in a BCl3/Ar-based plasma system and observed the performance of the thin-film surface after the etching process. The etch rate of the AZO thin films was highest at BCl3/Ar = 25:75, and increased as the power of the radio frequency source and bias increased. The etching mechanism was elucidated through optical emission and X-ray photoelectron spectroscopic analyses and confirmed to be the interaction between the bombardment of Ar ions and the chemical reaction of Cl and Cl2 radicals. BCl3-based plasma etching induces various changes in the properties of the AZO thin-film surface. The surface of the AZO thin film becomes very smooth, the work function increases by approximately 200 meV, and the bandgap increases by approximately 0.03 eV after the etching process in BCl3-based plasma. In addition, the electrical properties, such as sheet resistance and carrier mobility, are significantly improved. The results of this study may be applied for the development of high-performance optical and electronic devices. © 2021 Elsevier B.V.