High-Energy Backscattered Electron Imaging of Voids in Aluminum Metallizations

Abstract

ABSTRACTBackscattered electron imaging of microcircuits in scanning transmission electron microscopes at 120 kV is shown to produce improved images of voids in passivated Al metallization lines relative to those obtained with scanning electron microscopes at ≤ 40 kV. At 120 kV, resolutions of about 0.1 μm are achieved for voids imaged beneath 1.0 μm glass overlayers. This technique allows improved characterization of microstructures for basic investigations of void formation and more accurate counting of voids in microcircuits without removing glass overlayers. Smaller voids should also be detectable with the higher voltage.