Real-time SEM/FIB studies of whisker growth and surface modification

Abstract

We report on real-time measurements that enable us to watch the morphology of whiskers and hillocks forming in real-time and provide insight into the mechanisms controlling their growth and initiation. These measurements show that whiskers appear to grow out of a single grain on the surface with little lateral growth. To understand why whiskers initiate at specific sites, we modified the surface using the focused ion beam to remove the oxide in selected areas. Whiskers did not grow out of these uncovered areas, indicating that the underlying grain structure is important to whisker growth and it is not sufficient to just remove the oxide barrier. In comparison with whiskers, we found that hillock formation is accompanied by a large amount of grain growth and often by grain rotation at the surface.