Formation of dish-like holes and a channel structure in electrodeposition of copper under hydrogen co-deposition

Abstract

Copper electrodeposition from acid sulfate solutions at an overpotential of 1000 mV, which is about 250 mV outside the plateau of the limiting diffusion current density, was examined by the determination of the average current efficiency of hydrogen evolution and by the scanning electron microscopic (SEM) analysis of the morphology of the formed copper deposits. Craters or holes formed due to the attachment hydrogen bubbles were the dominant morphological forms of copper deposits obtained at this overpotential. In dependence of the concentration of Cu (II) ions in the plating solution, the two types of holes or craters were formed. One type of holes is obtained by electrodeposition from a solution with a concentration of Cu (II) ions of 0.075 M CuSO4 in 0.50 M H2SO4, and a honeycomb-like structure was formed from these holes. The other types of holes are formed from a solution with a higher concentration of Cu (II) ions (0.60 M CuSO4 in 0.50 M H2SO4) and the formed holes were dish-like. A mixture of both types of holes was obtained by electrodeposition from 0.30 M CuSO4 in 0.50 M H2SO4. The obtained morphologies of copper deposits are discussed in terms of the effect of hydrogen evolution on the hydrodynamic conditions in the plating solution.