Electrochemical Examination of Dendritic Growth on Electronic Devices in HCl Electrolytes

Abstract

As part of an investigation of electrochemical failure mechanisms occurring in electronic devices, factors affecting the formation and growth rate of dendrites on a model microelectronic device substrate have been examined. Experiments have been performed by immersing the devices in selected electrolytes and using a potentiostat to apply a constant cathodic potential or a constant potential bias. The effects of electrolyte composition and cathodic overpotential on dendrite formation and growth rate in HCl electrolytes have been delineated. Dendrites were observed at lower pH, but none were observed when the pH > 5.0, due to the formation of insoluble copper corrosion products such as Cu2O. Several features of the growth of dendrites in 0.1 M HCl electrolytes were observed to be similar to previous investigations: a minimum cathodic potential (approximately –0.450 V vs a saturated calomel electrode [SCE]) was required for the appearance and propagation of copper dendrites; at constant cathodic overpotential, the growth rate of dendrites was found to have a linear dependence on copper ion concentration; and the induction time prior to the detection of dendrites decreased as the cathodic overpotential increased. Although, experimentally measured dendrite growth rates were found to be up to three orders of magnitude smaller than theoretical predictions based on a maximum growth velocity model of dendrite growth, the model is still useful for predicting the functional dependence of velocity on a variety of electrochemical parameters. Suggestions for the development of an alternate, more accurate model are provided.