Embodiments described herein provide methods for forming indium-gallium-zinc oxide (IGZO) devices. A substrate is provided. An IGZO layer is formed above the substrate. A copper-containing layer is formed above the IGZO layer. A wet etch process is performed on the copper-containing layer to form a source region and a drain region above the IGZO layer. The performing of the wet etch process on the copper-containing layer includes exposing the copper-containing layer to an etching solution including a peroxide compound and one of citric acid, formic acid, malonic acid, lactic acid, etidronic acid, phosphonic acid, or a combination thereof.