Effects of Argon and Nitrogen ion Bombardments on Sputtered and Electroplated Cu Surfaces for Cu Bonding Application

This study depicts the comparative research between sputtered and electroplated Cu surfaces using argon and nitrogen ion bombardments to form copper nitride passivation layers. The thin copper nitride layer is formed in order to prohibit Cu oxidation on copper surface and to lower bonding temperature in Cu-Cu thermo-compression bonding process. Argon ion bombardment was applied to activate and clean copper surface. Nitrogen ion bombardment was utilized to passivate the Cu surface after argon ion bombardment. The sputtered Cu surface tended to form Cu4N layer, while the electroplated Cu surface tended to form Cu3N layer. In comparison with electroplated Cu, the sputtered Cu had a lower roughness and a slightly higher sheet resistance. The bonding quality of the sputtered Cu samples was better than that of the electroplated samples. Further research should improve the roughness and copper nitride properties of the Cu surface.