Spontaneous Potential Oscillation Resulting in Copper Deposit with Ultra-Large Grains

Abstract

There are three categories of spontaneous oscillations in copper electrodeposition. The first one is the formation of nano-scale multilayers of Cu2O and mixed Cu/Cu2O composites from an alkaline Cu2+-chelated solution. The second one is the formation of sub-microscale multilayers of Cu from a sulfuric acid system. The copper with sub-microscale multilayers composes of a series of horizontal grain boundaries, and the horizontal grain boundaries was formed with incorporation of organic compounds, namely plating additives. In this case, not only the grain boundaries are horizontal, but also the plating additives show a leveling capability to form a flat surface. The third one is the copper deposit formation with ultra-large grain (ULG) from a sulfuric acid plating system in this study. No organic compounds were incorporated in the copper-ULG and the surface, edges and corners of the copper-ULG, showing a single crystal outward appearance. The spontaneous oscillations waveform of ULG copper deposition was quite complicated, and it is caused by the changing/ageing of the organic compounds in the plating solution and the continuously changing of deposit surface area.