Contacts for highly scaled transistors
A semiconductor device and methods of forming the same are disclosed. The semiconductor device includes a substrate, first and second source/drain (S/D) regions, a channel between the first and second S/D regions, a gate engaging the channel, and a contact feature connecting to the first S/D region. The contact feature includes first and second contact layers. The first contact layer has a conformal cross-sectional profile and is in contact with the first S/D region on at least two sides thereof. In embodiments, the first contact layer is in direct contact with three or four sides of the first S/D region so as to increase the contact area. The first contact layer includes one of a semiconductor-metal alloy, an III-V semiconductor, and germanium.
1. A structure, comprising:
a substrate;
a first fin and a second fin rising above the substrate along a first direction;
an isolation structure spacing the first fin apart from the second fin along a second direction perpendicular to the first direction;
a first source/drain structure disposed over the first fin;
a second source/drain structure disposed over the second fin and merging with the first source/drain structure at a merged portion;
a dielectric layer disposed over the first source/drain structure, the second source/drain structure, and the isolation structure;
a semiconductor alloy layer extending through the dielectric layer to physically contact the first source/drain structure, the second source/drain structure and the merged portion; and
a void disposed between the first source/drain structure and the second source/drain structure along the second direction.
2. The structure of claim 1 , further comprising:
a metal layer disposed over the semiconductor alloy layer,
wherein the metal layer is spaced apart from the first source/drain structure, the second source/drain structure, the merged portion, and the dielectric layer by the semiconductor alloy layer.
3. The structure of claim 2 , wherein the metal layer comprises tungsten, copper, or cobalt.
4. The structure of claim 1 , wherein the semiconductor alloy layer comprises titanium, cobalt, nickel, nickel cobalt, other metals, or a combination thereof.
5. The structure of claim 4 , wherein the semiconductor alloy layer further comprises germanium (Ge), InAs, InGaAs, or InP.
6. The structure of claim 1 , wherein thicknesses of the first source/drain structure and the second source/drain structure along the first direction decrease toward the merged portion.
7. The structure of claim 1 , wherein the substrate, the first fin and the second fin comprise the same composition.
8. The structure of claim 1 ,
wherein, along the second direction, the void comprises a first width adjacent the isolation structure and a second width adjacent the merged portion,
wherein the first width is greater than the second width.
9. A structure, comprising:
a substrate;
a first fin and a second fin rising above the substrate along a first direction;
an isolation structure spacing the first fin apart from the second fin along a second direction perpendicular to the first direction;
a first diamond-shaped source/drain structure disposed over the first fin;
a second diamond-shaped source/drain structure disposed over the second fin and merging with the first diamond-shaped source/drain structure at a merged portion;
a dielectric layer disposed over the first diamond-shaped source/drain structure, the second diamond-shaped source/drain structure, and the isolation structure;
a semiconductor alloy layer extending through the dielectric layer to physically contact the first diamond-shaped source/drain structure, the second diamond-shaped source/drain structure and the merged portion; and
a void disposed between the first diamond-shaped source/drain structure and the second diamond-shaped source/drain structure along the second direction,
wherein the semiconductor alloy layer comprises titanium, cobalt, nickel, nickel cobalt, other metals, or a combination thereof.
10. The structure of claim 9 ,
wherein, along the second direction, the void comprises a first width adjacent the isolation structure and a second width adjacent the merged portion,
wherein the first width is greater than the second width.
11. The structure of claim 9 , wherein the semiconductor alloy layer further comprises germanium (Ge), InAs, InGaAs, or InP.
12. The structure of claim 9 , further comprising:
a metal layer disposed over the semiconductor alloy layer,
wherein the metal layer is spaced apart from the first diamond-shaped source/drain structure, the second diamond-shaped source/drain structure, the merged portion, and the dielectric layer by the semiconductor alloy layer.
13. A semiconductor structure, comprising:
a first fin;
a second fin spaced apart from the first fin by an isolation structure;
a first epitaxial feature disposed on the first fin;
a second epitaxial feature disposed on the second fin and merging with the first epitaxial feature at a merged portion;
an interlayer dielectric (ILD) layer over the first epitaxial feature, the second epitaxial feature and the merged portion;
a semiconductor alloy layer extending through the ILD layer to interface the first epitaxial feature, the second epitaxial feature and the merged portion; and
a metal layer disposed over the semiconductor alloy layer,
wherein a space between the first epitaxial feature and the second epitaxial feature as well as below the merged portion comprises a gap.
14. The semiconductor structure of claim 13 ,
wherein the merged portion is disposed directly over the isolation structure.
15. The semiconductor structure of claim 13 , wherein the semiconductor alloy layer comprises titanium, cobalt, nickel, nickel cobalt, other metals, or a combination thereof.
16. The semiconductor structure of claim 13 , further comprising:
a metal layer disposed over the semiconductor alloy layer.
17. The semiconductor structure of claim 16 , wherein the metal layer comprises tungsten, copper, or cobalt.
18. The semiconductor structure of claim 16 , wherein sidewalls of the metal layer are spaced apart from the ILD layer by the semiconductor alloy layer.
19. The semiconductor structure of claim 13 , wherein the merged portion is disposed between the gap and the semiconductor alloy layer.
20. The semiconductor structure of claim 13 , wherein the semiconductor alloy layer further comprises germanium (Ge), InAs, InGaAs, or InP.