Electrochemical Studies of Copper Chemical Mechanical Polishing Mechanism: Effects of Oxidizer Concentration
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ELECTROCHEMICAL STUDIES OF COPPER CHEMICAL MECHANICAL POLISHING MECHANISM: EFFECTS OF OXIDIZER CONCENTRATION J. Lu1, J.E. Garland2, C.M. Petite2, S.V. Babu 1,3,4, D. Roy2,3,5 Center for Advanced Materials Processing and Department of Physics Clarkson University, Potsdam, NY 13699, U.S.A.
Abstract The process of copper chemical-mechanical planarization (CMP) can be considered as an erosion corrosion process. Such a process can be efficiently studied by in situ and ex situ electrochemical techniques, such as potentiodynamic scan and electrochemical impedance spectroscopy (EIS). Using a copper disk as the working electrode in an electrochemical cell, slurries with different oxidizer concentrations have been investigated with the aforementioned techniques. Corresponding dissolution tests were also studied and compared. It is shown that changing the oxidizer concentration leads to the formation of surface films with different structure and composition on the copper surface during CMP process. The nature of these films controls the rate of copper corrosion. These results could be used to explain the change of copper removal rate in different oxidizer concentration, as well as to understand the copper CMP mechanism. Introduction CMP of copper has important technological applications in the field of integrated circuit (IC) fabrication. Along with the expansion of IC technologies, improving the efficiency of Cu-CMP has become a subject of intense investigation in recent years.1 Research efforts in this field have focused on both mechanical2 and chemical3,4 aspects of CMP. Among the different chemical techniques associated with CMP of Cu, a particular approach is now receiving considerable attention; it uses a peroxide-based polishing slurry containing an amino acid complexing agent glycine.3-6 In a recent work,7 we have studied such a system using Fast Fourier Transform Electrochemical Impedance Spectroscopy (FFT-EIS).8,9 The results obtained in that work provided an overall description of the main reaction steps that represent the chemical mechanism of Cu-CMP in peroxide-glycine slurries. In the present work, we explore further details of these reactions, and examine how they are affected by the peroxide-content (in the 0.25-5 wt% range) of the slurry. Chemical Mechanism of Cu-CMP In Glycine-Peroxide Slurries
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Center for Advanced Materials Processing, Box 5707 Department of Physics, Box 5820 3 Corresponding Authors 4 E-Mail: [email protected] 5 E-Mail: [email protected] 2
1 Downloaded from https://www.cambridge.org/core. Access paid by the UCSF Library, on 25 Oct 2019 at 13:09:56, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-767-F6.4
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To clarify in detail the specific goals of our present study, let us summarize our current understanding of the chemical effects of H2O2 and glycine on a Cu surface. A peroxide-based polishing slurry possibly oxidizes Cu as the following process; 2Cu + H2O2 = Cu2O + H2O, Cu2O + H2O2 = 2CuO + H
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