Small-signal AC resistance and DC resistance of evaporated pure Al interconnection were measured under the DC current stress which envokes electromigration. AC resistance weakly depends on frequency and increases as the frequency is lowered. This is compared with the fluctuation phenomenon in thin metal films which has been observed in flicker noise studies. Time dependent resistance change can be analized by the model of nucleation and growth of the voids in a metal film. Observed drop and preceding oscillaion in resistance can be interpreted as the evidence of the condensation of void nuclei and their phase transition into a macroscopic void.