Atomic flux divergence based finite element analyses were performed to show the difference in the electromigration failure mechanisms at different test conditions for Cu dual damascene line-via test structures. A combined driving force approach adapted in the model consists of driving forces from electron-wind, stress-migration and thermo-migration. It was shown that the failure mechanisms depend on the test condition and the stress free temperature of the structure. As the failure time depends on the failure mechanisms, the life-time prediction from accelerated test would be inaccurate if the invariability of failure mechanisms was assumed. It was also found that the interconnect life-time could be improved by lowering the final annealing temperature of the structure.

Effect of Test Condition and Stress Free Temperature on the Electromigration Failure of Cu Dual Damascene Submicron Interconnect Line-Via Test Structures. A.Roy, C.M.Tan, R.Kumar, X.T.Chen: Microelectronics and Reliability, 2005, 45[9-11], 1443-8