The activation energy for electromigration damage in Cu multi-layer interconnections was studied. The Cu multi-layer interconnections, with a width of about 0.7, were fabricated by means of Ar sputtering. The Al-Cu multi-layer interconnections were also prepared by using conventional processes. The current densities which were applied to the interconnections ranged from 16 to 24MA/cm2. After the electromigration tests, voids were found in the Cu layer of TiWN/Cu/TiWN multi-layers, and Cu hillocks formed at the anode side. The activation energies for electromigration damage of the Cu and Al-Cu interconnections were 0.97 and 0.62eV, respectively. The activation energies and times-to-failure of Cu and Al-Cu showed that the lifetime of the Cu interconnections at 110C was some 3 orders of magnitude longer than that of Al-Cu.

T.Fukada, T.Mori, Y.Toyoda, M.Hasegawa, K.Namba, K.Ogata: Applied Surface Science, 1995, 91, 227-33