Electrochemistry on microcircuits. II: Copper dendrites in oxalic acid

A new chip, which consists in an array of microelectrodes of various size and geometry, was realized by means of an industrial CMOS process. The microelectrodes were arranged as couples between which copper dendrites were able to grow in oxalic acid media up to short circuit the two electrodes. The current transient generated by the dendrite growth observed when a potential step was applied between the two microelectrodes was used to characterize the dendrite kinetics. In particular, the short circuit was detected when the current increased abruptly after some time called short circuit time. The influence of the oxalic acid concentration and of the geometry for the square-bar and lozenge-bar patterns on the short circuit time was investigated. At the end, some possibilities of partial inhibition of the dendritic growth were tested: addition of a supporting electrolyte, modification of the pH of the solution, addition of an inhibitor.