CVD Co film was investigated as an alternative barrier layer to the conventional PVD TaN\Ta in V1\M2 structure for 32nm node. We improved via filling performance and upstream (V1→M2) electromigration (EM) lifetime by more than three times. Excellent step coverage of CVD barrier makes it possible to reduce the thickness of the barrier metal by 30% and to increase the volume of Cu in metal lines. RC delay also reduced with decrease in resistance. Since adhesion at the interface between the barrier-Co and Cu also is strong, migration of Cu atoms is dramatically slowed down. EM in the via is finally deterred due to absence of pre-existing voids, consequently lifetime increases. This CVD Co process is expected to be beneficial for the next technology generation beyond 20nm node.
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