In the display industry, when making Array substrates with Cu process, the cleaning treatment will cause the corrosion of the Cu film. Through process adjustment, this paper has obtained the method that can control the mura brought by Cu corrosion within the specification. The corrosion products were analyzed by X‐ray photoelectron spectroscopy and Energy Dispersive Spectrometer. Surface morphology after cleaning was studied by scanning electron microscopy. We confirmed that the main constituent of mura was Cu(OH)2, and EUV irradiation to convert Cu2O into CuO was the key, which provided a theoretical basis for thoroughly solving the related problem.