Effect of barrier metal under first aluminum layer on reliability of interconnect vias and contact

It is shown that the lifetime due to electromigration is affected by the barrier metal under the first aluminum layer. The reliability of interconnect vias and contacts is greatly improved by using Ti/TiN barrier metal. The effect of barrier metals can be explained by the presence of Si nodules and hillocks at vias. In aluminum with MoSi, many Si nodules induced by MoSi were observed. These Si nodules degrade the reliability of interconnect vias. On the other hand, in aluminum with a Ti/TiN barrier, Si nodules and hillocks were extremely few