Changes in the electrical resistance of aluminum and copper interconnections caused by stress-induced migration were studied using simple numerical simulations. When residual thermal stress in an interconnection is not sufficiently relaxed, the electrical resistance increases with storage time; subsequently, the interconnection disconnects suddenly after a set period. In this case, it is difficult to determine the lifetime of an interconnection by measuring the electrical resistance in advance because of this abrupt increase in resistance. The lifetime of copper interconnections is longer than that of aluminum interconnections. Simulation results for aluminum interconnections agree with high-temperature storage tests. (c) 2006 American Vacuum Society.