Growth and Branching Mechanisms of Electrochemically Self-Organized Mesoscale Metallic Wires

Abstract

Electrochemical metallization with copper has been developed for on-chip interconnection in microelectronics. Therefore, the need for a detailed understanding of copper electrodeposition on the micrometer and nanometer scale is essential. In particular, approaches for the self-organized growth of mesoscale wires have become ofgreat interest recently. Here, we investigate the details of the deposit morphology of such mesoscale self-organized copper wires, focusing especially on the origin of the branching mechanism. The details of the morphology inform how the wires develop and why the branching occurs. It also shows that branching is not only associated with system noises but also with the electrical and concentration field and their coupling with interface growth. We demonstrate that by carefully adjusting the growth parameters branching can be avoided. In this way, highly ordered, periodic parallel arrays of metallic mesoscale wires were fabricated using this novel approach for self-organized growth by electrodeposition in ultrathin electrolyte layers. The results provide a general explanation for morphology formation during nonequilibrium electrocrystallization in thin electrolyte layers. This knowledge helps to develop processes for the controlled fabrication of micro- and nanostructured metallic patterns by electrochemistry.