Dependence of electromigration (EM) lifetime for via chains with conventional sputtered Al-Si-Cu films on slope angles of via holes has been investigated. EM testing for tapered (slope angle of 55 degrees) and vertical (slope angle of 85 degrees) via chains with 11 mu m long first metal lines and 12 mu m long second metal lines was performed under the same stress condition. Mean time to failure (MTF) bf the EM for the tapered via chains is one order of magnitude shorter than that for the vertical via chains, although the step coverage of the Al-Si-Cu films in the vias is improved by controlling the slope angle of the via hole for the tapered via. It was found that the MTF for the via chains degrades with decreasing the slope angle of the via hole. In this case, thicknesses of the local passivation Iayer in the via hole increase with decreasing the slope angle of the via hole because of improvement in the step coverage of the passivation layer. The MTF for the tapered via chains with a SiN/PSG dual passivation layer was 10 h, while that with a PSG single passivation layer was at least over 2000 h. It is inferred from these results that the thermal tensile stress induced in the Al film due to the thicker passivation layer increases the diffusivity of Al atoms in the vicinity of the via interface, which results in degradation of the EM resistance for the tapered via chains.