Study of synergy of monoethanolamine and urea on copper corrosion inhibition in alkaline solution

Abstract

• Cu corrosion in TMAH-containing solution is investigated. • MEA and urea are used as corrosion inhibitors to retard the Cu corrosion. • The synergy of MEA and urea on Cu corrosion inhibition is concentration ratio dependent. • Cu corrosion becomes more serious at low concentration ratio of MEA to urea. • Cu corrosion is effectively retarded at high concentration ratio of MEA to urea. Tetramethylammonium hydroxide (TMAH) is an important constituent used in the post cleaning process of chemical mechanical planarization and lithography; however, its corrosive property causes damage to the Cu metallization. Addition of corrosion inhibitor in the cleaning solution is a promising method to protect Cu. In this study, two corrosion inhibitors, monoethanolamine (MEA) and urea, are used to investigate their synergy on the Cu corrosion protection. Electrochemical and four-point probe methods are adopted to analyze the corrosion behaviors of Cu. Microstructural characterizations of Cu are performed using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. X-ray photoelectron spectroscopy is used to realize the adsorption behaviors of inhibitors on the Cu surface. The results of corrosion current ( I corr ) and charge transfer resistance ( R ct ) indicate that addition of MEA and urea at an identical concentration does not produce a typical synergistic effect on the Cu corrosion protection due to mutual interference of two inhibitors. An increase of the MEA concentration overcomes the mutual interference, giving rise to a reduction of I corr and an increase of R ct . The effective retardation of the Cu corrosion is attributed to the sufficiency of inhibitors which can construct a dense protection layer on the Cu surface.