A study of aluminum sputter deposition parameters and TiW barrier surface effects on electromigration

This work investigates the impact of thin-film processing parameters on the electromigration (EM) performance of an AlSi/TiW metallization system. The results show that the EM performance of aluminum on a TiW barrier is worse than that of a nonbarrier film and that oxidizing and/or nitriding the TiW barrier prior to AlSi deposition improves fine-line EM performance by more than an order of magnitude. However, the wide-line EM performance is reduced by a factor of two. It is concluded that the EM performance of the AlSi/TiW film is dominated by the interface of the films and is not significantly changed by the AlSi sputter deposition parameters. The effect is shown to be related to the aluminum grain size. The grain size is increased from about 0.8 μm to 4.0-5.0 μm when the TiW is exposed to atmosphere prior to aluminum deposition