Daniel Josell, Maureen E. Williams, Stephen J. Ambrozik, Chen Zhang, Thomas P. Moffat
This work extends previously detailed void-free, bottom-up feature filling in a near-neutral Na3Au(SO3)2 + Na2SO3 electrolyte containing micromolar concentrations of Bi. Bottom-up electrodeposition in 17 m and 45 m tall trenches is demonstrated using either potentiostatic, stepped potential and/or stepped current control. Strategies to shorten the incubation period associated with slow deposition on uniformly passivated surfaces, which precedes bottom-up filling at fixed potential, are explored. The first electron back scatter diffraction studies of bottom-up filled Au deposits reveal large grains that span the trench width and often exceed tens of micrometers in length. In contrast, smaller grains are observed near the tops of filled trenches and, under conditions of marginal filling, mid-height within them.