A composite metallization of Al over doped poly‐Si should exhibit superior electromigration resistance, since even after the Al develops an open circuit, the poly‐Si would be expected to provide electrical continuity. However, results indicate that poly‐Si reduces the lifetime of Al by a ×2 and a further decrease occurs over stepped topographies. Thus, while electron beam evaporated Al/poly‐Si exhibits acceptable lifetimes, induction‐source Al/poly‐Si may be only marginal in this regard. Failures occur predominantly at steps by nonuniform grain boundary diffusion in Al, until the metal opens up. This followed by the electromigration of Si into Al and localized melting.