Effects of deposition modes on the microstructure of copper deposits from an acidic sulfate bath

The electrodeposition of various copper deposits was carried out by means of cyclic voltammetric, potentiostatic, galvanostatic, pulse-rest and pulse-reverse plating modes in a simple acidic CuSO4 bath without any additives, although the 8 mM CuSO4 solution employed in this work was not practically applicable for electroplating. The morphologies of these Cu deposits were systematically compared by atomic force microscopy (AFM), and scanning electron microscopy (SEM). The average grain size and roughness of Cu deposits were found to strongly depend on the deposition modes. From the results of SEM and AFM, the Cu deposit plated by cyclic voltammetry showed the smoothest and most compact morphology with the smallest average grain size. When the deposition potentials were negative to −0.17 V, nucleation of Cu seeds and growth of Cu grains occurred simultaneously, resulting in the presence of relatively small Cu clusters on the deposit grains. The anodic process through means of either cyclic voltammetry or reverse plating rendered the significant dissolution of grain peaks and these small Cu clusters on the deposit, resulting in a relatively smooth surface.