Adhesion Improvement for Copper Process in TFT-LCD

The first issue that should be overcome in copper process is its poor adhesive strength between pure copper film and glass substrate. In this study, defining the adhesive strength of pure copper film on various substrates and clarifying the key deposition parameters are presented for the investigation of copper process. First, using different kinds of surface plasma treatments were studied and the results showed that the adhesive strength was not improved even though the roughness of glass substrate surface was increased. Second, adding an adhesive layer between glass substrate and pure copper film was used to enhance the adhesion. Based on the data in the present paper, adopting copper alloy film as an adhesive layer can have capability preventing peeling problem in copper process. Besides, Cu/Cu alloy structure could be etched with the same etchant with better taper angle than the one with single layer of Cu. Unlike Cu/Mo structure, there is no residual problem for Cu/Cu alloy structure during etching process. Finally, this structure was examined in electrical test without significant difference in comparison with the conventional metal process.