Comprehensive electromigration studies on dual-damascene Cu interconnects with ALD WCxNy barriers

Am important improvement in electromigration (EM) resistance was revealed upon the introduction of atomic-layer-deposited WCN barriers in dual-damascene Cu interconnects. At stress level EM failure were found to increase with WCN thickness and to be consistently superior compared to I-PVD deposited barriers. Although the voiding scenario is identical for both ALD and I-PVD barriers, a reduction of the current density exponent and the activation energy is observed for ALD. In contrast to the influence of WCN barrier thickness on the EM behaviour, the effect of specific pre-clean procedures prior to the ALD process turned out to the less pronounced.