Surface topology changes during electromigration in metallic thin film stripes

Electromigration damage in silver and aluminum thin film stripes was observed by scanning electron microscopy. Early formation of voids and surface growths occured in regions of maximum temperature and in the same cross-section. Once formed, void damage was comparatively stable, and failure ultimately occurred at the cathode end of the stripes. The growths in the aluminum stripe were nucleated at grain boundaries and were restricted to the boundary. The flux of atoms into one growth was approximated to be 2 X 108 atoms h-1. Growths in the silver stripe were not restricted by the grain size but had the appearance of surface undulations. Large protrusions appeared in coincidence with a catastrophic upswing in stripe resistance. It is felt that local failure of a thin oxide and subsequent "extrusion" may be responsible for this behavior. © 1969.