Electrochemical examination of surface films formed during chemical mechanical planarization of copper in acetic acid and dodecyl sulfate solutions

• Published in: Thin solid films 2009-06, Vol.517 (16), p.4587-4592
• Main Authors: Zheng, J.P., Roy, D.
• Format: Article
• Language: English
• Subjects: Acetic acid; Condensed matter: structure, mechanical and thermal properties; Copper chemical mechanical polishing; Electron, ion, and scanning probe microscopy; Exact sciences and technology; Impedance spectroscopy; Other nonelectronic physical properties; Physical properties of thin films, nonelectronic; Physics; Rotating disc electrode; Structure and morphology; thickness; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Surfactant; Thin film structure and morphology
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2009.03.063

Electrochemical impedance spectroscopy (EIS) is employed to study the competitive reactions of surface corrosion and passivating film formation on a Cu-rotating disc electrode (RDE) in pH-adjusted solutions of H 2O 2, acetic acid (HAc) and ammonium dodecyl sulfate (ADS). The surface reactions that occur at the open circuit potential of this system are relevant for chemical mechanical planarization (CMP) of Cu-interconnect structures. The results show how the discontinuous film of Cu-oxides formed by H 2O 2 acts both to dissolve (via reactions with HAc) and to passivate the Cu surface. The relatively more continuous ADS film serves as a dissolution suppressor and regulates the removal of Cu/Cu-oxide surface layers. The results presented here also demonstrate the utility of EIS involving RDEs to design slurry chemistries for Cu-CMP.