The effects of dielectric layers upon electromigration failure were studied in situ by using high-voltage scanning electron microscopy and conventional accelerated testing. Various passivation layers were deposited onto wafers with Al interconnect test structures, following identical prior processing. Interconnects with compliant polymer and 0.1µm-thick SiO2 layers exhibited marked lifetime extensions as compared with those having more rigid 1µm-thick SiO2 layers. Unpassivated lines behaved very differently, and failed much sooner than did those covered with 0.1µm of SiO2. Increasing the passivation thickness, from 0.5 to 4µm, increased the electromigration lifetime of SiO2-covered specimens.

Effects of Dielectric Materials on Electromigration Failure. J.C.Doan, S.Lee, S.H.Lee, P.A.Flinn, J.C.Bravman, T.N.Marieb: Journal of Applied Physics, 2001, 89[12] 7797-808