In situ x-ray microscopic observation of the electromigration in passivated Cu interconnects

X-ray imaging of electromigration in a passivated Cu interconnect was perfo rmed with 100-nm spatial resolution. A time sequence of 200 images, recorde d with the European Synchrotron Radiation Facility x-ray microscope in 2.2 h at 4 keV photon energy, visualizes the mass flow of Cu at current densiti es up to 2x10(7) A/cm(2). Due to the high penetration power through matter and the element specific image contrast, x-ray microscopy is a unique tool for time-resolved, quantitative mass transport measurements in interconnect s. Model calculations predict that failures in operating microprocessors ar e detectable with 30 nm resolution by nanotomography. (C) 2001 American Ins titute of Physics.