US Patent 9269612 Mechanisms of forming damascene interconnect structures

An interconnect structure includes a first trench and a second trench. The second trench is wider than the first trench. Both trenches are lined with a diffusion barrier layer, and a first conductive layer is deposited over the diffusion barrier layer. A metal cap layer is deposited over the first conductive layer. A second conductive layer is deposited over the metal cap layer in the second trench.