Electromigration experiments were performed for Al-based interconnects of samples with and without air exposure after barrier layer deposition and prior to Al deposition. The intention of air exposure was normally performed to improve the efficiency of barrier layer against the Al diffusion. However, the electromigration performance of such air exposed samples was found to be controversial. It was found that in the case of highly accelerated tests, the electromigration lifetime decreased and failure rate increased for samples with air exposure, while these variations were found to be negligible in the case of moderate accelerated tests. Finite element analyses revealed that high temperature gradient exists in the metallization at highly accelerated test and this gradient enhances the atomic flux divergence due to triple point formed by titanium nitride, titanium oxide and Al.

Effect of Vacuum Break after Barrier Layer Deposition on the Electromigration Performance of Aluminum Based Line Interconnects. C.M.Tan, A.Roy, K.T.Tan, D.S.K.Ye, F.Low: Microelectronics and Reliability, 2005, 45[9-11], 1449-54