The via resistance analysis at ALD-to-PVD TaN transition layer

We demonstrate that when a thin ALD (atomic layer deposition) TaN as a barrier metal is deposited to the Cu interconnect, the upper via resistance is significantly increased. We also exhibit that the abnormal upper via resistance is consistent with the N/Ta increase by nitrogen diffusion. To overcome this issue, we investigate a hybrid TaN (PVD TaN on the top of ALD TaN), which prevents the nitrogen diffusion to the bottom of the upper via, resulting in the improvement of the upper via resistance.