- Conference date: 29−31 Mar 1993
- Location: Austin, Texas (USA)
Electromigration was studied from two aspects: a detailed observation of hillocks by transmission electron microscopy and scanning electron microscopy, and a statistical analysis of the densities and sizes of voids and hillocks. The detailed observation revealed that hillocks do not form new aluminum grains but that the growth of pre‐existing grains forms hillocks. That is, the growth points are within the grains, not at the surfaces. It is suggested that plastic deformation processes such as lattice diffusion, dislocation motion, and grain boundary slide other than grain boundary diffusion take part in hillock formation. The statistical analysis revealed that voids and hillocks have a uniform but not random distribution. Intervals between voids and between a void and the next hillock are some characteristically distributed with an average that depends on the current density. The number of voids and hillocks formed per unit conductor length by electromigration is proportional to the current density. This relationship can contribute to the increasing dependence of conductor lifetime on current density (Black’s relationship).
- Current density
- Grain boundaries
- Statistical analysis
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