Interconnection and electromigration scaling theory

Interconnections will become the limit in performance and reliability at submicrometer dimensions. Long-distance interconnections are defined using models based on resistivity, and it is found that more than half of the interconnections will become categorized as such at 0.5-µm feature sizes. The resistivity of even less resistive materials, therefore, will become important. A model for analyzing the trends of material usage for interconnections and for projecting design rules is presented. Electromigration is the driving force away from the lowest resistivity silicon compatible material, namely aluminum. Replacements such as gold, however, have technological problems and the resistivity of refractory metals will be too high for a large fraction of the interconnections. Layered structures are one possible solution to the problems of electromigration and hillocks.