<title>Barrier layer effects and the use of Ti:W capping layers on the electromigration performance of Al-Si(1%)-Cu(0.5%) alloy</title>

Electromigration performance is investigated for Al-Si(1%)-Cu(0.5%) alloy on a CVD-W or Ti:W barrier layer, and the effectiveness of a Ti:W capping layer to suppress electromigration is explored. Compared to a Ti:W barrier layer, the surface roughness of the CVD-W barrier layer degrades electromigration performance, however, a capping layer of Ti:W sequentially sputtered on top of the aluminum-alloy will substantively improve the electromigration performance when either barrier layer system is used. The improvement is observed to increase with the thickness of the Ti:W capping layer. Investigations of the failure kinetics and material properties indicate the EM performance improvement is primarily due to changes in the Al-alloy micro-structure.