Direct Copper Pattern Plating on Glass and Ceramic Substrates Using an Al-Doped ZnO as an Adhesive and Conducting Layer

Three substrates, Al2O3, AlN and glass, were directly metallized by copper electroplating using Al-doped ZnO (AZO) as an adhesive and conducting layer between these substrates and the electroplated copper layer. The AZO was synthesized in sol-gel solution, where the Al content in the AZO sol-gel was 2 at.%. Because the AZO is a conductor that can be etched by an acidic solution, copper patterns can be directly electroplated on these substrates coated with the patterned AZO. The AZO patterns went through dry film coating, pattern formation and dry film removal process steps. Two direct copper pattern electroplating processes were proposed in this work, where one process could protect the patterned AZO from being undercut because AZO layer was patterned first and then copper was directly electroplated on the patterned AZO; the other process could not do so because copper was electroplated on the AZO layer and then both the electroplated copper layer and the AZO layer were simultaneously patterned. The copper electroplating solution must be alkaline; otherwise the AZO coated on the substrates would be etched in an acidic copper electroplating solution.