Abstract
Surface atomic steps in unpassivated copper lines under electromigration (EM) have been directly observed in ultrahigh vacuum by in situ transmission electron microscopy (in situ TEM). The combination of {111} planes and 〈110〉 directions for crystalline Cu were found to be the most favored EM paths. The in situ TEM study of EM-induced evolution of Cu surface structures provides a sound basis for understanding the dependence of EM-induced atomic migration mechanism on crystal orientation of crystalline Cu. The understanding shall lead to the effective strategy of using appropriate passivation layer to suppress the electromigration. c 2007 American Institute of Physics.