Dissolution Inhibition in Cu-CMP Using Dodecyl-Benzene-Sulfonic Acid Surfactant with Oxalic Acid and Glycine as Complexing Agents

This work demonstrates that the anionic surfactant, dodecyl-benzene-sulfonic acid (DBSA), is an effective dissolution inhibitor in chemical mechanical planarization (CMP) of Cu. Material removal rates were measured employing slurries, with and without DBSA, containing an oxidizer H 2 O 2 and glycine, oxalic acid (OA), or a glycine-OA mixture as the complexing agent. Polishing was performed at a down-pressure of 2 psi using fumed silica particles. The OA-based slurries supported chemically dominant material removal, which would be useful for processing structures containing fragile low-k dielectrics, and, unlike certain other anionic surfactants, DBSA provided effective surface protection in these systems. Optical profilometry showed that blanket Cu-wafer surfaces, polished with DBSA, were noticeably defect-free. The glycine-OA mixed-complexing-agent system in combination with DBSA yielded most satisfactory results, showing effective suppression of Cu dissolution (∼0 nm/min), as well as providing substantial polish rates with good postpolish surface finish. Considerations for postpolishing cleaning of DBSA were explored using contact-angle measurements. The electrochemical techniques of dc polarization and ac Fourier transform impedance spectroscopy were employed to examine the surface chemistries of a rotating-disk Cu electrode under polishing conditions at 40°C in the absence and in the presence of DBSA.