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

Abstract

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 and glycine, oxalic acid (OA), or a glycine–OA mixture as the complexing agent. Polishing was performed at a down-pressure of using fumed silica particles. The OA-based slurries supported chemically dominant material removal, which would be useful for processing structures containing fragile low- 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 , 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 in the absence and in the presence of DBSA.