Microstructural Origins of Saccharin-Induced Stress Reduction in Electrodeposited Ni

In this work, we provide direct evidence of the fundamental mechanism through which saccharin, a standard industrial Ni electroplating additive, reduces stress in electrodeposited Ni. This was accomplished using real-time in situ stress measurements taken during through-mask electrodeposition of Ni films from a bath where the saccharin concentration was varied. This technique facilitated the direct measure of the effect of saccharin on the stress created at the Ni island boundaries. We demonstrated that increased saccharin concentration in a Ni-sulfamate-based bath resulted in a systematic reduction in the tensile grain-boundary coalescence stress. Based on this and ex situ S concentration measurements of the Ni films, we propose that the reduction in tensile stress was the result of a reduction in the grain-boundary energy due to S incorporation at the island boundaries.