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This report studies the electromigration performance of W-plug via structures under the reservoir effect. The lifetime improvement factor M was observed to be a weak function of the stressing current and approximately equal to 2. A Simple model is included in the report to explain this observation. The model also predicts the most effective reservoir length for electromigration lifetime improvement.

The electromigration (EM) performance of W-plug via-fed lead test structures has been investigated. It was observed that the median time-to-failure (MTTF) and time-to- ailure dispersion (σ) depended on the number of vias servicing the lead. With multiple-vias feeding the metal lead, the early times-to-failure tended to be suppressed. In general, as the number of W-plug vias feeding the metal lines increases, MTTF tended to increase and σ tended to decrease. Also, the activation energy (0.85 eV) observed during this via-fed EM study is consistent with reports of interfacial diffusion.

This letter reports the effects of via current density on electromigration (EM) failure in Al–0.5 Cu conductors. Two-level metallization structures, differing in the number of feeding vias (1, 6, and 15), were made with the same pattern of Al lines at two levels to allow simultaneous EM testing of upper- and lower-level lines. It was established that the lower-level lines were more susceptible to the impact of the via, resulting in a failure by the formation of a local void beneath a via and a strong dependence of EM lifetime on the via current density. The results led to a phenomenological equation that incorporates via structure into failure kinetics.

The temperature-composition phase diagram of the Ni-Cr system was calculated using a first-principles approach based on a statistical-mechanical approximation for the configurational entropy and a tigh-binding method for electronic structure calculations. A self-consistent tight-binding Hamiltonian with only d-electrons was implemented by imposing a condition of zero charge transfer. Hamiltonian parameters were taken from the results of first-principles band-structure calculations. The effects of self-consistent d-electron numbers for pure Ni and Cr on the phase diagram and thermochemical properties were also investigated.