AlSiCu/Ti(TiN)//TiN/Ti interconnect structures, which have been fabricated by depositing a Ti or TiN additional layer on the TiN/Ti barrier exposed in atmospheric ambient and then by depositing AlSiCu on the additional layer without breaking vacuum, have shown improved electromigration lifetimes. These were 1.9 and 6.5 times longer than that of the conventional AlSiCu//TiN/Ti structure, for the TiN and Ti additional layer, respectively. From an analysis of these results, it has been assumed that elongated lifetimes were caused by an enhancement of the Al(111) crystallographic orientation in the AlSiCu/TiN//TiN/Ti structure, and caused by both a reduction of the Si nodule concentration in AlSiCu due to Al-Si-Ti ternary alloy formation and Al(111) texture further enhanced by the additional Ti underlayer in the AlSiCu/Ti//TiN/Ti structure.