Investigation of Corrosion Mechanisms of Copper Microstructures Underneath Polymer Coatings: Experiment and Simulation

Abstract

BACKGROUND Reliability and stability of electronic components are crucial for both consumer and producer. External influences (e.g. bias, humidity) can enable corrosion processes and lead to accelerated failure. For example, field-driven electrochemical migration (ECM) of copper (Cu), a material that is widely used for electrical connections, can drive corrosion processes and ultimately lead to component failure. METHODOLOGY In this work, a miniaturized test chip, manufactured with techniques used in the semiconductor industry, is employed to investigate ECM and corrosion mechanisms of copper electrodes covered by an organic coating. Combinations of applied bias and aqueous electrolytes atop the organic layers are used to drive ions into and inside the coating. The distribution of ions in the polymer layer and at the interface Cu/coating is investigated by optical, electrochemical and analytical methods (e.g. EIS, LA-ICP-MS). The experimental work is complemented with a dynamic multi-ion finite element simulation model created with COMSOL Multiphysics®. The simulation model of polymer coated copper structures is developed starting from a previous electrochemical model of Cu electrodes in aqueous electrolytes, which was validated experimentally. Refinement and validation is achieved by comparison with literature and experimental data acquired through test chip measurements. RESULTS The course of current and solution resistance transients determined by EIS show the slow progression of corrosion processes until a fast breakdown is observed. Experimental results and the comparison with simulation enable insights into electrochemical migration of Cu and corrosion mechanisms. The combination of the two helps elucidate corrosion processes and thereby allows the identification of on-going electrochemical processes in electronic components at different stages.