Growth and recrystallization of electroplated copper columns

The present paper addresses the formation and evolution of microstructure and crystal structure of electroplated copper columns. Copper columns of different size have been plated on Au seed layer for a series of periods of time from half an hour to three hours and characterized by Focused Ion Beam (FIB) and XRD. It was found that not only the growth process during plating but also accompanying recrystallization and post-plating spontaneous self-annealing account for the interesting microstructure with bi-modal or tri-modal grain size distribution. The evolution of crystal structure of the copper columns during plating and self-annealing after plating was also studied and discussed. The results indicate that the presence of organic additives is not essential for self-annealing to occur in copper columns, which is against the popular belief with respect to electroplated copper films.