By FIB, TEM, and EDS analyses, we observed the near-bamboo structured Al-Cu interconnect terminated with W plugs before and after electromigration (EM), and investigated Cu and Al atomic behavior during EM. While Cu atoms were supersaturated in the Al-Cu line before EM,&thgr;-Al2Cuprecipitates were found only in the anode side after EM. It indicates that transportation of Cu atoms from the cathode side toward the anode side occurred by electron wind. Amorphous layers of the order of 10 nm thickness were found to exist on both side walls of the Al-Cu line before and after EM. After EM, voids were found to be formed inside the amorphous layer along side walls of Al-Cu layer. It is supposed that interface between the amorphous layer and the Al-Cu line side wall is a dominant diffusion path of Al atoms in the case of near-bamboo structured Al-Cu line. We found that the surface of the void after EM was either (111) or (110) faceted plane. It is supposed that a diffusion path of Al atoms on the surface of the void cannot be explained only by the surface energy of lattice plane. ©1998 American Institute of Physics.