Investigation of copper corrosion mechanisms in convection-free aqueous media using a thin layer test cell and simulation

Abstract

Organic coatings (OCs) are commonly employed to protect micro-electronic components from external influences (e.g. bias, humidity), to avoid corrosion of the metal conductors. Copper (Cu), widely used as electric conductor, requires such protection to prevent component failure caused by dendrite growth, which is driven by electrochemical migration (ECM). However, OCs can also degrade over time. The ingress of water to the metal/OC interface is assumed to enable corrosion processes at the metal conductors [1]. In this work, a “thin layer cell” is implemented, to investigate ECM, dendrite growth and corrosion mechanisms of copper electrodes in nearly convection-free aqueous media, that approximates the conditions occurring at the micro-electronic component metal/OC interface. This approach enables better control of the medium properties, such as counter ions and pH, to characterize their influences on the corrosion behavior. Besides, it gives fast corrosion response, other than at the micro-electronic component scale, where high isolating and low permeability properties of the OC slow down the electro-chemical processes. The “thin layer cell” consists of two thin, parallel copper plates (used as working and counter electrode), that are sandwiched between two glass plates, yielding a defined electrolyte volume in between, in which a reference electrode is inserted. Combinations of bias, counter ions, pH and concentration of Cu2+ ions are investigated by optical and electro-chemical analytic methods. Using literature data and experimental results, a dynamic multi-ion simulation model is developed using COMSOL Multiphysics. Experimental results and the comparison with simulation enable insights on Cu corrosion mechanisms and dendrite growth, thus giving a possibility to predict corrosion and allowing a better understanding of on going electrochemical processes at different stages in non-convective environments.

[1] Lyon, S. B., Bingham, R., & Mills, D. J. (2017). Advances in corrosion protection by organic coatings: What we know and what we would like to know. Progress in Organic Coatings, 102, 2-7.