Interfacial characterization of Cu/Ru bimetallic corrosion: Effect of polyphenol antioxidants

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Shyam S. Venkataraman, sam_unt@yahoo.com, Kyle K. Yu, walrusyu@gmail.com, Karthik S. Pillai, karthik_unt@yahoo.com, Fan Yang, yangfan1984111@yahoo.com, Praveen N. Reddy, Chyan@unt.edu, and Oliver Chyan, chyan@unt.edu. Department of Chemistry, University of North Texas, PO # 305070, Denton, TX 76203-5070
Bimetallic corrosion can occur when dissimilar metals are placed in electrical contact under environment with electrolytes. Ruthenium (Ru) has been a leading candidate as the new diffusion barrier for Cu interconnects for the next generation integrated circuit devices. In this paper, we report an interfacial study of the autoxidation of gallic acid and its related polyphenols in bimetallic corrosion of Cu on Ru and Ta substrates. Autoxidation of gallic acid is greatly enhanced by increase in the pH forming different oxidized products with peroxide as the by-product. Our experimental results indicate that Gallic acid corrodes Cu only at low basic conditions, however no Cu corrosion can be seen either at acidic or at more alkaline conditions (pH > 11). Formations of different oxidized products of Gallic acid are characterized using different techniques like cyclic voltammetry, differential pulse voltammetry, UV-Vis spectroscopy and infrared spectroscopy. A detailed mechanism is proposed for the Cu/Ru bimetallic corrosion in polyphenols.