The computer aided vacancy migration analysis due to hydrostatic stress distribution was developed to predict SiV lifetime in an organic ultra low-k dielectric or silicon oxide / Cu interconnects. The SiV acceleration tests were carried out in various widths of Cu lines and these results were compared with the vacancy migration analysis. The narrower line indicated to be higher SiV failure rate in organic dielectric, while a remarkable failure rate increase in a certain width of line were observed in SiO2 dielectric. The value of vacancy concentration obtained by the vacancy migration analysis showed similar behavior. These results reveal that the vacancy migration analysis is a practical to apply to predict reliability of interconnects.