Copper electrodeposition: Principles and recent progress

The capability of copper electroplating to produce void free filling of sub-micron high aspect ratio features has made it the process of choice for copper interconnect formation, Several aspects of copper electrodeposition including the basic electrochemistry and electrochemical kinetics, mass transport phenomena, potential gradients in solution, electrolyte composition, and the influence of various organic additives have been studied for over 50 years. Much of this basic understanding can be applied to development of integrated circuit (IC) copper electroplating processes. Other aspects of copper electroplating are unique to IC applications, These include the interactions of very thin seed layers with the electroplating process, the basic "bottom-up" filling mechanism necessary for seam free filling, and the metallurgical properties of sub-micron scale deposits. The dependence of IC filling processes upon plating bath chemistry and polarization characteristics arc discussed in this paper.