In Situ Observation of Electromigration in Cu Film Using Scanning µ-Reflection High-Energy Electron Diffraction Microscope

Abstract

We have observed void and hillock formation at the grain boundary and inside the grain in the Cu line due to electromigration (EM), by means of in situ nondestructive imaging of micrograins using a scanning µ-reflection high-energy electron diffraction (µ-RHEED) microscope. Accelerated electromigration testing was performed at a dc current density of 5×106 A/cm2 and at 250°C in the scanning µ-RHEED microscope. The triple point of grain boundaries was confirmed to weaken the EM endurance. Furthermore, we conjectured that high EM endurance inside the grain could be achieved with the current flow along the <011> direction for fcc metal such as Cu.