New Insights into the Modulation of Island Density of Electrodeposits Using Pulsatile Waveforms

Abstract

Electroplating with dynamic voltage pulsing, also termed pulsed electroplating, is becoming popular in controlling the grain size, surface morphology, and growth dynamics. In the present work, the hitherto less explored effects of pulse time scales (i.e., temporal distributions of zero and nonzero potentials), frequency, and waveform on the dynamics of nucleation-induced island density during copper electrodeposition were quantified in a specifically designed electrochemical setup by optical microscopy. The images were analyzed to highlight significant effects of applied voltage, electrolyte concentration, etc. on the transient island density, surface coverage, and average island size. The efficacy of pulsed electrodeposition was benchmarked against that of its equivalent DC counterpart. The study confirmed the existence of a limiting state below which pulse electrodeposition was noted to produce the same island density as that of the constant potential (DC) experiment despite intermittent zero-potential states in any pulse function. Additionally, the effects of waveforms over the nonzero potential state (ON-time) of any pulse were investigated using four different ramp-type functions. Interestingly, the specific waveform with an initial positive slope outperformed the others in terms of the higher island density. The results unambiguously demonstrated the effectiveness of pulsed potential waveforms in electrodeposition and conform to the basic physics of the process.