Origin of stress gradients induced in capped, copper metallization

Abstract

Stress gradients generated near the top surface of Cu thin films by capping layers, as measured using a combination of conventional and glancing incidence x-ray diffraction, exhibit heterogeneous behavior that is directly related to plastic anisotropy within the Cu grains. A comparison of stress gradients measured from several x-ray reflections to their corresponding Schmid factors yields a consistent, critical resolved shear stress. The results experimentally verify that dislocation-mediated plasticity is responsible for the creation of stress gradients at the Cu film/cap interface. Depth-dependent measurements reveal that the observed gradients are localized to within 200 nm of this interface. © 2014 AIP Publishing LLC.