Voidless contact metal structures
Voidless contact metal structures are provided. In one embodiment, a voidless contact metal structure is provided by first providing a first contact metal that contains a void within a contact opening. The void is then opened to provide a divot in the first contact metal. After forming a dielectric spacer atop a portion of first contact metal, a second contact metal is then formed that lacks any void. The second contact metal fills the entirety of the divot within the first contact metal. In another embodiment, two diffusion barrier structures are provided within a contact opening, followed by the formation of a contact metal structure that lacks any void.
1. A method of forming a contact structure, said method comprising:
providing, from bottom to top, a base structure and a dielectric structure, wherein a conductive material portion is embedded in said base structure, and wherein a contact opening is located within said dielectric structure and exposes a topmost surface of said conductive material portion and vertical sidewall surfaces of said dielectric structure;
forming a first continuous diffusion barrier layer within said contact opening, wherein said first continuous diffusion barrier layer contacts an entire exposed topmost surface of said conductive material portion and is in direct contact with said entire exposed vertical sidewall surfaces of said dielectric structure, and wherein said first continuous diffusion barrier layer contains an overhang region located in an upper portion of said contact opening;
etching said upper portion of said first continuous diffusion barrier layer to remove said overhang region and to expose an upper portion of said vertical sidewall surfaces of said dielectric structure, while maintaining a lower portion of said first continuous diffusion barrier layer in said contact opening, wherein said lower portion of said first continuous barrier layer includes a horizontal portion that is present on said entire topmost surface of said conductive material portion;
forming a second continuous diffusion barrier layer directly on entire exposed surfaces of said first continuous diffusion barrier layer including said horizontal portion of said first continuous diffusion barrier layer, said exposed upper portion of said vertical sidewall surfaces of the dielectric structure, and a topmost surface of said dielectric structure;
forming a contact metal within said opening and directly on said second diffusion barrier layer; and
removing portions of said contact metal and said second diffusion barrier layer that are present on said topmost surface of said dielectric structure, wherein after removing portions of said contact metal and said second diffusion barrier layer that are present on said topmost surface of said dielectric structure, a topmost surface of a remaining portion of said contact metal and a topmost surface of a remaining portion of said second diffusion barrier layer are coplanar with each as well as being coplanar with said topmost surface of said first diffusion barrier layer and said topmost surface of said dielectric structure.
2. The method of claim 1 , wherein said etching process comprises an anisotropic etch.
3. The method of claim 1 , wherein said first diffusion barrier layer and second diffusion barrier layer comprise a same diffusion barrier material.
4. The method of claim 1 , wherein said first diffusion barrier layer and second diffusion barrier layer comprise different diffusion barrier materials.
5. The method of claim 1 , wherein said contact metal comprises a conductive metal or a metal alloy.
6. The method of claim 1 , wherein said removing said portions of said contact metal and said second diffusion barrier layer further removes an upper portion of said dielectric structure.
7. The method of claim 6 , wherein said removing portions of said contact metal and said second diffusion barrier layer comprises a planarization process.
8. The method of claim 7 , wherein after performing said planarization process, a U-shaped second diffusion barrier portion remains in said contact opening.
9. The method of claim 1 , wherein said conductive material portion embedded in said base structure is a doped semiconductor material, and said doped semiconductor material is surrounded on both sides by a semiconductor material.
10. The method of claim 1 wherein said conductive material portion embedded in said base structure is at least one of an elemental metal, an alloy of at least two elemental metals, an elemental metal nitride, an elemental metal silicide, and a doped semiconductor material, and said conductive material portion is surrounded on both sides by an insulator material.
11. The method of claim 1 , wherein said forming said contact metal is performed without forming a void in said contact metal.