Abstract
Atomic-scale electromigration (EM) in unpassivated copper metal lines was directly observed in ultrahigh vacuum at room temperature by transmission electron microscopy. It was found that copper atoms on a (211) crystal plane vanished directionally within half an hour when applying an electric current with a density of 2× 106 A cm2 through the tested Cu line. The EM-induced atomic migration appeared to be anisotropic, and the combination of {111} planes and 〈110〉 directions was suggested to be the easiest electromigration system for crystalline copper. EM-induced mass transport was also found to be responsible for the weakening (111) texture of the Cu lines after electric current stressing. c 2005 American Institute of Physics.