Suppression of bimodal stress-induced voiding using high-diffusive dopant from Cu-alloy seed layer

The effect of impurity doping to Cu from Cu-alloy (CuSn and CuTi) seed layer on stress-induced voiding in Cu dual-damascene interconnects has been investigated. Significant suppression of both voiding inside vias and under vias was observed for CuSn. In addition, CuSn had 9 times the electromigration resistance of pure Cu, with available increments of sheet resistance. The difference in terms of reliability improvement between the doping materials is due to higher diffusivity of Sn into Cu in comparison to Ti. We have demonstrated high reliable Cu dual-damascene interconnects using high-diffusive dopant in the Cu-alloy seed layer.