Effect of sulfuric acid concentration on the quality of copper microcolumns in localized electrochemical deposition

Abstract

Localized electrochemical deposition (LECD) is a promising method for three-dimensional micro-/nanofabrication and, thus, the factors influencing LECD have been intensively investigated. This study examined the effect of sulfuric acid concentration on copper microcolumns deposited by LECD using a microanode with a diameter of 20 μm. With 0.05 mol l-1 sulfuric acid, the deposition voltage of the optimal deposited morphology of copper microcolumns was at 2.9 V, but the column diameter was larger than the anode diameter. With 0.5 and 2.0 mol l-1 sulfuric acid, the optimal deposited morphology of copper microcolumns were at 3.2 V and 3.4 V, respectively, but the diameters of the copper microcolumns were smaller than the anode diameter. In the LECD process, the deposition rate is proportional to the deposition voltage. Because of the hydrogen evolution, the deposition rates of copper microcolumns at high sulfuric acid concentration were lower than those at low and medium sulfuric acid concentrations. The results of this study indicated that the deposition rate obtained the optimal surface topography was 0.22 to 0.327 um s-1, which had reference significance to improve the quality of the copper microcolumns. The effect of sulfuric acid on the LECD was demonstrated using a competitive reduction mechanism.