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;
forming a diffusion barrier portion within a lower portion of said contact opening and a first contact metal structure on said diffusion barrier portion, wherein a divot is present at an upper portion of said first contact metal structure, wherein forming said diffusion barrier portion within said lower portion of said contact opening and said first contact metal structure on said diffusion barrier portion comprises:
depositing a contiguous layer of a diffusion barrier material within said contact opening and on said topmost surface of said dielectric structure;
forming a first contact metal on said contiguous layer of said diffusion barrier material, wherein a void is present in said first contact metal;
removing portions of said contiguous layer of said diffusion barrier material and said first contact metal that are present on said topmost surface of said dielectric structure; and
recessing remaining portions of said diffusion barrier material and said first contact metal to provide said diffusion barrier portion and said first contact metal structure;
forming a pair of spaced apart dielectric spacers within said contact opening and on a topmost surface of said diffusion barrier portion and a portion of a topmost surface of said first contact metal structure, wherein each dielectric spacer has a sidewall surface contacting a sidewall surface of said dielectric structure; and
forming a second contact metal structure within said contact opening and between said pair of dielectric spacers, wherein a portion of said second contact metal structure completely fills said divot present in said first contact metal structure.
2. The method of claim 1 , wherein said forming said pair of dielectric spacers comprises:
depositing of a dielectric spacer material; and
etching said dielectric spacer material.
3. The method of claim 1 , wherein said forming said second contact metal structure comprises:
depositing a second contact metal; and
removing portions of said second contact metal that are located outside said contact opening.
4. The method of claim 1 , wherein a topmost surface of diffusion barrier portion is coplanar with a topmost surface of said first contact metal structure.
5. The method of claim 1 , wherein a topmost surface of said second contact metal structure is coplanar with said topmost surface of said dielectric structure.
6. 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.
7. The method of claim 1 , wherein said conductive material portion embedded in said base structure comprises 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.