N-work function metal with crystal structure
A method includes forming a dummy gate stack over a semiconductor substrate, wherein the semiconductor substrate is comprised in a wafer. The method further includes removing the dummy gate stack to form a recess, forming a gate dielectric layer in the recess, and forming a metal layer in the recess and over the gate dielectric layer. The metal layer has an n-work function. A portion of the metal layer has a crystalline structure. The method further includes filling a remaining portion of the recess with metallic materials, wherein the metallic materials are overlying the metal layer.
1. A device comprising:
a semiconductor substrate;
an Inter-Layer Dielectric (ILD) layer over the semiconductor substrate;
gate spacers in the ILD; and
a replacement gate in the ILD and between opposite portions of the gate spacers, wherein the replacement gate comprises:
a high-k gate dielectric layer, wherein the high-k gate dielectric layer has a cross-sectional view of a U-shape, and the high-k gate dielectric layer comprises a bottom portion and sidewall portions over, and connected to opposite ends of, the bottom portion;
a diffusion barrier layer over the bottom portion of the high-k gate dielectric layer; and
an n-type work-function layer over the diffusion barrier layer, wherein the n-type work-function layer is a compound, and the compound comprises titanium and aluminum, and the n-type work-function layer comprises portions having crystalline structures.
2. The device of claim 1 , wherein all portions of the n-type work-function layer with the crystalline structures have a total volume percentage higher than about 80 percent of a total volume of the n-type work-function layer.
3. The device of claim 1 , wherein the crystalline structures comprises portions having crystalline directions selected from the group consisting of a (200) crystalline direction, a (201) crystalline direction, a (111) crystalline direction, and combinations thereof.
4. The device of claim 3 , wherein the crystalline structures comprise a portion with a (111) crystalline direction.
5. The device of claim 1 , wherein the high-k gate dielectric layer comprises an oxide selected from hafnium oxide, lanthanum oxide, and aluminum oxide.
6. The device of claim 1 further comprising:
a titanium nitride layer over the n-type work-function layer; and
a filling metal over the bottom portion of the n-type work-function layer.
7. The device of claim 6 further comprising a blocking layer over the titanium nitride layer, wherein the blocking layer comprises titanium nitride.
8. The device of claim 6 , wherein the filling metal comprises aluminum.
9. The device of claim 1 further comprising:
a wetting layer over the n-type work-function layer.
10. The device of claim 9 , wherein the wetting layer comprises cobalt.
11. The device of claim 1 , wherein the crystalline structures of the n-type work-function layer comprises a hexagonal close packing structure.
12. The device of claim 1 , wherein the n-type work-function layer comprises a titanium aluminum compound.
13. The device of claim 1 , wherein more than 5 volume percent of the n-type work-function layer is crystalline.
14. The device of claim 1 , wherein the diffusion barrier layer is selected from the group consisting essentially of a titanium nitride layer, a tantalum nitride layer, and a composite layer comprising a titanium nitride layer and a tantalum nitride layer over the titanium nitride layer.
15. A device comprising:
a first gate spacer and a second gate spacer;
a high-k gate dielectric extending between the first gate spacer and the second gate spacer, wherein the high-k gate dielectric comprises a bottom portion and sidewall portions having bottom ends connected to opposite ends of the bottom portion;
a titanium-aluminum-containing layer over the high-k gate dielectric, wherein the titanium-aluminum-containing layer includes at least a portion having a (111) crystalline direction;
a blocking layer over the titanium-aluminum-containing layer; and
a filling metal overlying the blocking layer, wherein the titanium-aluminum-containing layer, the blocking layer, and the filling metal are between the first gate spacer and the second gate spacer.
16. The device of claim 15 , wherein the blocking layer is in contact with the titanium-aluminum-containing layer.
17. The device of claim 15 further comprising a diffusion barrier selected from the group consisting essentially of a titanium nitride layer, a tantalum nitride layer, and a composite layer comprising a titanium nitride layer and a tantalum nitride layer over the titanium nitride layer.
18. The device of claim 15 , wherein more than 80 volume percent of the titanium-aluminum-containing layer are crystalline.
19. The device of claim 15 , wherein the titanium-aluminum-containing layer comprises portions having (200) and (201) crystalline directions.
20. The device of claim 19 , wherein the titanium-aluminum-containing layer further comprises portions having a (111) crystalline direction.
21. The device of claim 15 , wherein more than 5 volume percent of the titanium-aluminum-containing layer is crystalline.
22. The device of claim 15 , wherein the blocking layer comprises titanium nitride.
23. The device of claim 15 , wherein the titanium-aluminum-containing layer comprises a titanium aluminum compound.
24. The device of claim 15 , wherein the filling metal comprises aluminum.
25. A device comprising:
a first gate spacer and a second gate spacer;
a high-k gate dielectric, wherein the high-k gate dielectric has a cross-sectional view of a U-shape, and the high-k gate dielectric comprises a bottom portion and sidewall portions over, and connected to opposite ends of, the bottom portion;
a first metal-containing layer over the bottom portion of the high-k gate dielectric, wherein the first metal-containing layer comprises crystalline portions, and the first metal-containing layer is an n-type work-function layer; and
a second metal-containing layer over the first metal-containing layer, wherein the second metal-containing layer is formed of a material different from first metal-containing layer, and wherein the high-k gate dielectric, the first metal-containing layer, and the second metal-containing layer extend between the first gate spacer and the second gate spacer.
26. The device of claim 25 , wherein the first metal-containing layer comprises a titanium aluminum compound.
27. The device of claim 26 further comprising a titanium nitride layer between the high-k gate dielectric and the first metal-containing layer that comprises the titanium aluminum compound.
28. The device of claim 25 , wherein the high-k gate dielectric comprises an oxide selected from hafnium oxide, lanthanum oxide, and aluminum oxide.
29. The device of claim 25 , wherein the first metal-containing layer further comprises crystalline portions having a (111) structure.
30. The device of claim 25 , wherein each of the first metal-containing layer and the second metal-containing layer comprises:
a bottom portion; and
sidewall portions having bottom ends connected to opposite ends of the bottom portion.
31. The device of claim 25 , wherein more than 80 volume percent of the first metal-containing layer are crystalline.
32. The device of claim 25 further comprising a wetting layer over the second metal-containing layer, wherein the wetting layer comprises titanium nitride.
33. The device of claim 32 , wherein the wetting layer comprises cobalt.
34. The device of claim 25 further comprising a filling metal over the second metal-containing layer.
35. The device of claim 34 , wherein the filling metal comprises aluminum.
36. The device of claim 25 , wherein more than 5 volume percent of the first metal-containing layer is crystalline.
37. The device of claim 25 further comprising a blocking layer over the second metal-containing layer, wherein the blocking layer comprises titanium nitride.
38. The device of claim 25 , wherein the high-k gate dielectric comprises an oxide selected from hafnium oxide, lanthanum oxide, and aluminum oxide.
39. The device of claim 25 further comprising a diffusion barrier layer between the high-k gate dielectric and the first metal-containing layer, wherein the diffusion barrier layer is selected from the group consisting essentially of a titanium nitride layer, a tantalum nitride layer, and a composite layer comprising a titanium nitride layer and a tantalum nitride layer over the titanium nitride layer.