Electro-migration reduction

1. An interconnect structure, comprising:

a conductive feature embedded in a dielectric layer;

a capping barrier layer disposed over the conductive feature and the dielectric layer; and

an adhesion layer sandwiched between the capping barrier layer and the dielectric layer,

wherein the adhesion layer comprises a degree of crystallinity between about 40% and about 70%.

2. The interconnect structure of claim 1 , wherein the dielectric layer comprises amorphous silicon oxide.

3. The interconnect structure of claim 1 , wherein the capping barrier layer comprises aluminum nitride.

4. The interconnect structure of claim 1 , wherein the adhesion layer is disposed over the conductive feature.

5. The interconnect structure of claim 1 , wherein the adhesion layer comprises beta silicon nitride.

6. The interconnect structure of claim 1 , wherein the adhesion layer comprises hexagonal silicon oxide, hexagonal silicon carbide, diamond cubic silicon, tetragonal titanium oxide, hexagonal chromium oxide, or hexagonal aluminum oxide.

7. The interconnect structure of claim 1 , further comprising:

a conductive capping layer disposed between the conductive feature and the capping barrier layer.

8. A semiconductor structure, comprising:

a contact feature in a dielectric layer, the contact feature comprising

a metal fill layer,

a barrier layer disposed between the metal fill layer and the dielectric layer, and

a conductive capping layer over the metal fill layer and the barrier layer;

a capping barrier layer disposed over the conductive capping layer and the dielectric layer; and

an adhesion layer sandwiched between the capping barrier layer and the dielectric layer,

wherein the capping barrier layer comprises aluminum nitride.

9. The semiconductor structure of claim 8 , wherein the dielectric layer comprises amorphous silicon oxide.

10. The semiconductor structure of claim 8 , wherein the conductive capping layer comprises cobalt.

11. The semiconductor structure of claim 8 , wherein the adhesion layer comprises beta silicon nitride, hexagonal silicon oxide, hexagonal silicon carbide, diamond cubic silicon, tetragonal titanium oxide, hexagonal chromium oxide, or hexagonal aluminum oxide.

12. The semiconductor structure of claim 11 , wherein the adhesion layer comprises a degree of crystallinity between about 40% and about 70%.

13. The semiconductor structure of claim 8 , wherein the barrier layer comprises titanium, titanium nitride, tantalum, tantalum nitride, molybdenum, ruthenium, nickel nitride, tungsten nitride, copper nitride, manganese nitride, or cobalt nitride.

14. A method, comprising,

receiving a workpiece including a dielectric layer and a conductive feature embedded in the dielectric layer;

forming an adhesion layer on a top surface of the dielectric layer; and

depositing a capping barrier layer over the adhesion layer,

wherein the capping barrier layer comprises aluminum nitride.

15. The method of claim 14 , wherein the dielectric layer comprises amorphous silicon oxide and the conductive feature comprises copper and manganese.

16. The method of claim 14 , further comprising:

after the forming of the adhesion layer, annealing the workpiece to increase a degree of crystallinity of the adhesion layer.

17. The method of claim 14 , wherein the depositing of the capping barrier layer comprises use of atomic layer deposition (ALD).

18. The method of claim 14 , wherein the adhesion layer comprises silicon nitride, silicon oxide, silicon carbide, silicon, titanium oxide, chromium oxide, or aluminum oxide.

19. The method of claim 14 , further comprising:

before the forming of the adhesion layer, selectively depositing a cobalt layer over the conductive feature.

20. The method of claim 19 ,

wherein, after the forming of the adhesion layer, the adhesion layer is absent from a top surface of the cobalt layer.