Advanced elemental analysis methods for sub 30nm defects in a defect review SEM

Abstract

as development phases became shorter, fast defect characterization is highly important. In addition, new chemicals involved in sub 28nm semiconductor processes introduce new types of defects. The variety of defect types complicates defect root cause analysis, so that image based defect analysis is limited, and defect material information becomes more important. Thus elemental analysis of defects in a defect review SEM gains importance in sub 28nm processes.This work presents a new type of Energy Dispersive X ray Spectrometer (EDX), integrated together with a unique e-beam column and high collection solid angle. It allows x-ray count rates that are more than an order of magnitude higher compared to traditional detectors. The high count rate speeds up the analysis period to less than 2 seconds for sub 30nm defects. Short analysis time is critical for such small sized defects as they can disappear due to charging or evaporation. In addition, the new detector-column configuration becomes sensitive to very thin films (down to 1nm), something that was not reasonable for the traditional SiLi x-ray spectrometers.Traditional EDX requires >5keV beam energies and >500pA beam current. New layers that are introduced to < 40nm processes, such as Ultra Low K materials, are sensitive to high electron doses. The new, fast EDX allows defect analysis on sensitive layers without damaging the analysis area