X-ray micro-beam study of reliability in aluminum-copper interconnect lines

X-ray photoemission spectroscopy and x-ray diffraction are powerful techniques widely used in materials research. The advent of synchrotron radiation facilities as high brightness x-ray sources and recent advances in x-ray optics have extended these techniques to spatially resolved measurements with sub-micron resolution. We have used two such facilities to study two major reliability problems in integrated circuit interconnect technology: electromigration and mechanical stress induced problems.; MAXIMUM at the Advanced Light Source (ALS) is a scanning photoemission microscope based on multilayer coated normal incidence optics. It acquires images of surfaces that map chosen spectral features from photoelectron emission spectra. In situ electromigration experiments were performed in the ultra high vacuum chamber of MAXIMUM on patterned Al-Cu lines. The results demonstrate a Cu rich surface precipitation, changes in Cu distribution as a result of the electromigration process and the detection of shallow voids under the surface oxide layer.; The X-ray micro-beam facility at the Advanced Photon Source (APS) uses diffractive Fresnel Zone Plates to focus intense undulator light into a sub-micron size beam. Microdiffraction experiments were performed to map the stress distribution along patterned Al-Cu lines with a {dollar}sim{dollar}1 {dollar}mu m{dollar} resolution for the first time. Diffraction patterns from single grains were recorded on an x-ray CCD camera and techniques developed to analyze the two dimensional micro-diffraction data for strain-stress analysis. An increase of grain to grain and intra-grain stress variation was found after accelerated electromigration testing. Contrary to predictions, no long range variation of stress due to electromigration was observed.; These observations demonstrate the usefulness and potential of x-ray micro-characterization techniques in the electronic materials area.