Electromigration characterization of damascene copper interconnects using normally and highly accelerated tests

We have completed a set of experiments on damascene Chemical Vapor Deposition Copper (CVD-Cu) interconnects using Wafer Level and Package Level Reliability (WLR and PLR) tests. Two line widths have been extensively characterized : w=4 and 0.6 mu m For both line widths, the activation energy values extracted using WLR and PLR data are in good agreement demonstrating that the active diffusion paths remain the same over the wide range of used measurement conditions : Ea=0.65eV for w=4 mu m, Ea=0.7-0.8eV for w=0.6 mu m. Moreover, Scanning Electron Microscope (SEM) observations gave evidences of grain boundary diffusion in spite of Ea experimental values lower than the reference values of the literature. (C) 2000 Elsevier Science Ltd. All rights reserved.