| CPC H01L 21/76846 (2013.01) [H01L 21/76873 (2013.01); H01L 21/76886 (2013.01); H01L 23/5226 (2013.01); H01L 23/53209 (2013.01); H01L 23/53266 (2013.01); H01L 21/76813 (2013.01); H01L 21/76831 (2013.01); H01L 21/76834 (2013.01); H01L 21/76877 (2013.01); H01L 21/76882 (2013.01); H01L 23/485 (2013.01); H01L 23/532 (2013.01); H01L 23/53295 (2013.01)] | 19 Claims |

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1. A method for forming an interconnect structure, the method comprising:
forming a cobalt-containing contact directly on a first source/drain feature, wherein the cobalt-containing contact includes a cobalt-containing bulk layer, the cobalt-containing contact has an upper portion above a top surface of a gate structure, the cobalt-containing contact has a lower portion below the top surface of the gate structure, the upper portion is formed in a first interlayer dielectric layer and a first contact etch stop layer, and the gate structure is disposed between the first source/drain feature and a second source/drain feature;
forming a tungsten-containing via directly on the cobalt-containing contact, wherein the tungsten-containing via is formed in a second interlayer dielectric layer and a second contact etch stop layer, wherein the forming the tungsten-containing via includes:
forming a tungsten-containing bulk layer, and
forming a titanium-and-nitrogen-containing barrier layer along a bottom and a sidewall of the tungsten-containing bulk layer; and
forming a copper-containing trace directly on the tungsten-containing via, wherein the copper-containing trace is formed in a third interlayer dielectric layer and a third contact etch stop layer;
wherein the gate structure is a first gate structure and the lower portion of the cobalt-containing contact and the first source/drain feature are disposed between the first gate structure and a second gate structure.
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