Organic Acid Mixing to Improve ITO Film Etching in Flat Panel Display Manufacturing

This study examines how oxalic acid mixed with tartaric acid affect indium tin oxide (ITO) etching. When the ITO films were etched with the mixed solutions of oxalic acid and tartaric acid, the dissociation of tartaric acid impeded the formation of oxalate ion and decreased the etching rate of ITO films. Furthermore, the potential–pH diagrams for indium and tin in oxalic acid and tartaric acid systems reveal that indium oxide could be dissolved to form In ( C 2 O 4 ) 2 − in oxalic acid etchants, and that indium oxide and tin oxide were both soluble in the mixed etchants of oxalic acid and tartaric acid. Additionally, the X-ray photoelectron spectroscopy results demonstrate that the removal rate of SnO 2 was slower than that of In 2 O 3 in oxalic acid etchants, which induced many residues after the etching process. However, adding tartaric acid to oxalic acid increased the dissolution rate of tin oxide and decreased the level of residues. Consequently, the ITO etching by oxalic acid with tartaric acid shows a more uniform pattern than that by only oxalic acid.