Coulometric reduction (CR) has been widely used to study atmospheric copper corrosion and tarnishing phenomena and to measure the copper corrosion rate. To find other CR applications, this technique was used to study the reaction of copper electrodes with fluorine-containing plasmas used for silicon etching. Copper samples were submitted to SF6-plasma environments and the CR time of the chemical species formed over the surface was measured. The CR test was made using a fixed cathodic current density (0.05 mA/cm(2)) to obtain voltage-time data (E vs. t). Two plateaus, at around -550 and -750 mV, were found. The -550 mV plateau corresponds to Cu2O reduction. Additional CF4-plasma exposure tests and Rutherford backscattering spectroscopy analysis indicated that the -750 mV plateau corresponds to a Cu-F compound. Surprisingly no Cu2S was detected by CR. CR is a fast technique that proved to be useful in determining, in a qualitative way, chemical reactions that take place at the electrode surface in silicon-etching microelectronic processes. There must be further study of the potential of this technique as a quantitative tool. (C) 2003 The Electrochemical Society.