Electromigration Investigations of Al-Cu Interconnect Reliability

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9975893HeskettWith the continual shrinking of semiconductor devices, failures due to electromigration-induced damage in metal interconnects have become a significant problem and concern. It has been known for some time that the addition of small amounts of copper in aluminum interconnects increases their resistance to electromigration. However, the exact role of this copper is not well understood. In this proposal the PIs will combine theoretical modeling with a variety of experimental techniques to examine and clarify the role of copper in the early stages of electromigration-induced damage of aluminum alloy interconnects. Furthermore the PIs will develop a reliable method for extrapolating the results of accelerated stress tests to normal operating conditions.Specific outcomes of their work will include the following:1. Development of a microscopic model of the electromigration process.2. Reevaluation of the conventional model used to extrapolate the results of accelerated stress tests. (Determination of the correct temperature dependence in "Black's Law".)3. Determination of the physical meaning of the stress-induced activation energy for copper and aluminum diffusion in Al-Cu metal lines.4. Determination of copper and aluminum-copper precipitate mobility in these systems as well as the specific role they play in blocking aluminum diffusion.5. Rutherford Backscattering measurements of the current-induced diffusion of copper in Al-Cu interconnects.6. Focused Ion Beam measurements of the role of film morphology (i.e. grain size distribution) in electromigration.These studies will directly address a real world problem in the microelectronics industry and will result in a significant advance in current understanding of metal diffusion under highly stressed conditions.***