Fine-Line Patterning of Transparent Ga-Doped ZnO Thin Films by Wet-Etching

A photolithography processing and wet-etching technology for use in forming ZnO transparent electrodes that are just a few micrometers in line-widths for application to Liquid Crystal Display (LCD) panels was developed. The chemicals (developed or obtained commercially) used for the photolithography process included a strong alkaline photoresist-developer, an alkaline photoresist-stripper with pH11-13 and a weak acidic etchant with pH 5.5-6.8 suitable for ZnO compound films with amphoteric properties. Optimization of the process conditions for photolithography and etching played a critical part in the development of the technology. We succeeded in forming transparent fine-patterns of Ga-doped ZnO films with 4 micronmeter line-widths and space-widths using this method. These fine line sizes indicate that our technology has reached a technical level comparable to those used for forming the ITO fine-pattern electrodes currently used for commercially available LCD panels.