Effect of vacuum break after the barrier layer deposition on the electromigration performance of aluminum based line interconnects

Electromigration (EM) experiments have been performed for aluminum (Al) based interconnect of samples with and without air exposure after barrier layer deposition and prior to aluminum deposition. The intention of air exposure is normally performed to improve the efficiency of barrier layer against the Al diffusion. However, the EM performance of such air exposed samples is found to be controversial. It has been found that in the case of highly accelerated tests, the EM life-time decreases and failure rate increases for the samples with air exposure, while these variations has been found to be negligible in the case of moderate accelerated tests. Finite element analyses reveal 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 aluminum.