Interconnect voiding failures caused by stress-induced migration were investigated by analysis of atomic diffusion mechanisms using simple numerical computations for aluminum and copper interconnects. The activation energy for the voiding failure of aluminum interconnects, assuming that the lattice diffusion of atoms is the primary diffusion mechanism of stress-induced migration, was calculated to be approximately 0.8 eV, which was close to the activation energy obtained from actual high-temperature storage tests (i.e., 0.5–0.6 eV). This agreement implies that for aluminum interconnects the assumption is correct, and the lattice diffusion is the primary diffusion mechanism for stress-induced migration. The computed activation energy for voiding failure of copper interconnects was less than 1.5 eV and did not agree with the activation energy obtained from high-temperature storage tests (0.74 eV). The calculated interconnect lifetime was approximately six orders of magnitude larger than that obtained from the high-temperature storage tests. These results suggest that lattice diffusion is not the primary diffusion mechanism for stress-induced migration in copper interconnects.