Source/drain via having reduced resistance
A source/drain is disposed over a substrate. A source/drain contact is disposed over the source/drain. A first via is disposed over the source/drain contact. The first via has a laterally-protruding bottom portion and a top portion that is disposed over the laterally-protruding bottom portion.
1. A device, comprising:
a source/drain disposed over a substrate;
a source/drain contact disposed over the source/drain;
a first via disposed over the source/drain contact, wherein the first via has a laterally-protruding bottom portion and a top portion that is disposed over the laterally-protruding bottom portion, and wherein the top portion has tapered sidewalls in a cross-sectional side view;
a first interlayer dielectric (ILD) disposed over the substrate, wherein the first ILD at least partially surrounds the source/drain contact laterally;
an etching-stop layer disposed over the first ILD, wherein the laterally-protruding bottom portion is disposed in the etching-stop layer; and
a second ILD disposed over the etching-stop layer, wherein the top portion is disposed in the second ILD.
2. The device of claim 1 , further comprising:
a gate structure disposed over the substrate; and
a second via disposed over the gate structure, wherein the first via and the second via have substantially co-planar upper surfaces.
3. The device of claim 2 , wherein the first via and the second via are offset with respect to one another in both an X-direction and a Y-direction in a top view.
4. The device of claim 2 , further comprising: a glue layer disposed on side surfaces and a bottom surface of the second via.
5. The device of claim 4 , wherein the glue layer contains titanium or titanium nitride.
6. The device of claim 1 , wherein a first maximum lateral dimension of the laterally-protruding bottom portion is greater than a second maximum lateral dimension of the top portion.
7. The device of claim 1 , wherein the source/drain contact and the first via have different metal material compositions.
8. The device of claim 1 , wherein an uppermost surface of the source/drain contact is narrower than a bottommost surface of the first via.
9. The device of claim 1 , wherein the laterally-protruding bottom portion is in direct contact with the source/drain contact.
10. The device of claim 1 , wherein:
the tapered sidewalls are first sidewalls;
the laterally-protruding bottom portion has second sidewalls in the cross-sectional side view; and
the first sidewalls are more tapered than the second sidewalls in the cross-sectional side view.
11. A device, comprising:
a source/drain disposed over a substrate;
a gate structure disposed over the substrate;
a first interlayer dielectric (ILD) disposed over the gate structure;
an etching-stop layer disposed over the first ILD;
a second ILD disposed over the etching-stop layer;
a gate via disposed over the gate structure, wherein the gate via extends vertically through the first ILD, the etching-stop layer, and the second ILD;
a glue layer disposed between the gate via and the first ILD, the etching-stop layer, and the second ILD;
a source/drain contact disposed over the source/drain, wherein the source/drain contact extends vertically through the first ILD; and
a source/drain via disposed over the source/drain contact, wherein the source/drain via extends vertically through the second ILD and the etching-stop layer, wherein an uppermost surface of the gate via is co-planar with an uppermost surface of the source/drain via, and wherein a bottommost surface of the source/drain via is wider than the uppermost surface of the source/drain via;
wherein:
sidewalls of a bottom segment of the source/drain via are in direct physical contact with sidewalls of the etching-stop layer;
sidewalls of a top segment of the source/drain via are in direct physical contact with sidewalls of the second ILD; and
the bottom segment and the top segment have substantially different shapes in a cross-sectional side view.
12. The device of claim 11 , wherein:
the bottom segment is substantially wider than the source/drain contact; and
the sidewalls of the top segment are more tapered than the sidewalls of the bottom segment.
13. The device of claim 11 , wherein the source/drain via and the gate via are offset from each other in both a first horizontal direction and a second horizontal direction that is perpendicular to the first horizontal direction in a top view.
14. The device of claim 11 , wherein the glue layer contains titanium or titanium nitride.
15. A device, comprising:
a source/drain disposed over a substrate;
a source/drain contact disposed over the source/drain; and
a source/drain via disposed over the source/drain contact, wherein the source/drain via has a laterally-protruding bottom portion and a top portion that is disposed over the laterally-protruding bottom portion, wherein side surfaces of the top portion have a slanted profile in a cross-sectional side view, and wherein a bottom surface of the laterally-protruding bottom portion is wider than a top surface of the top portion in the cross-sectional side view;
a first interlayer dielectric (ILD) disposed over the substrate, wherein the first ILD at least partially surrounds the source/drain contact laterally;
an etching-stop layer disposed over the first ILD, wherein the laterally-protruding bottom portion is located within the etching-stop layer; and
a second ILD disposed over the etching-stop layer, wherein the top portion is located within the second ILD.
16. The device of claim 15 , further comprising:
a gate structure disposed over the substrate; and
a gate via disposed over the gate structure, wherein the gate via and the source/drain via have substantially co-planar upper surfaces, wherein the source/drain via and the gate via are separated from one another in both a first horizontal direction and a second horizontal direction in a top view.
17. The device of claim 16 , further comprising: a glue layer disposed on side surfaces and a bottom surface of the gate via, wherein the glue layer contains titanium or titanium nitride.
18. The device of claim 15 , wherein:
the source/drain contact and the source/drain via have different material compositions; and
an uppermost surface of the source/drain contact is wider than the bottom surface of the laterally-protruding bottom portion of the source/drain via.
19. The device of claim 15 , wherein a bottom surface of the source/drain via is in direct contact with a top surface of the source/drain contact.
20. The device of claim 15 , wherein the top portion of the source/drain via is more slanted than the laterally-protruding bottom portion of the source/drain via in the cross-sectional side view.