Amorphous layers for reducing copper diffusion and method forming same

1. A method comprising:

forming a first conductive feature over a substrate;

forming an amorphous metal cap on the first conductive feature;

depositing a dielectric layer over the amorphous metal cap;

etching the dielectric layer to form an opening; and

filling the opening with a conductive material to form a second conductive feature contacting the amorphous metal cap.

2. The method of claim 1 , wherein the forming the amorphous metal cap comprises:

forming a metal cap comprising a polycrystalline structure; and

performing a treatment process on the metal cap to convert the metal cap into the amorphous metal cap, wherein the treatment process comprises bombarding the metal cap.

3. The method of claim 2 , wherein the treatment process is performed using a process gas that comprises a nitrogen-containing process gas.

4. The method of claim 3 , wherein the process gas further comprises, and wherein a hydrogen-to-nitrogen atomic ratio of the process gas is in a range between about 1 and about 3.

5. The method of claim 2 , wherein the forming the metal cap comprises:

treating the first conductive feature with a nitrogen-containing process gas to form a copper nitride layer; and

conducting a metal-containing process gas to the copper nitride layer, wherein the metal-containing process gas comprises a metal, and wherein the metal cap comprises a nitride of the metal.

6. The method of claim 1 further comprising:

depositing a first etch stop layer over the first conductive feature, wherein the dielectric layer is deposited over the first etch stop layer; and

performing a treatment process to amorphize the first etch stop layer.

7. The method of claim 6 , wherein the depositing the first etch stop layer is performed at a temperature in a range between about 300° C. and about 380° C.

8. The method of claim 6 further comprising, after the second conductive feature is formed, performing a high-temperature process, wherein the first etch stop layer is converted to have polycrystalline structures.

9. The method of claim 6 further comprising:

depositing a second etch stop layer over the first etch stop layer; and

depositing a third etch stop layer over the second etch stop layer, wherein the dielectric layer is formed over the third etch stop layer, and the opening further extends through the third etch stop layer and the second etch stop layer.

10. The method of claim 1 , wherein the forming the amorphous metal cap comprises forming a cobalt nitride layer.

11. A method comprising:

forming an etch stop layer over a first conductive feature;

depositing a dielectric layer over the etch stop layer;

etching the dielectric layer to form an opening, wherein the etch stop layer is exposed through the opening;

etching-through the etch stop layer to extend the opening into the etch stop layer; and

filling the opening with a conductive material to form a second conductive feature, wherein at a first time after the second conductive feature is formed, the etch stop layer has an amorphous structure.

12. The method of claim 11 further comprising, at a second time that is after the first time, performing a thermal treatment process to convert the etch stop layer as a polycrystalline layer.

13. The method of claim 11 , wherein the forming the etch stop layer comprises:

depositing the etch stop layer; and

performing a treatment process to convert the etch stop layer as an amorphous layer.

14. The method of claim 13 , wherein before the treatment process, the etch stop layer has a polycrystalline structure.

15. The method of claim 11 , wherein the forming the etch stop layer comprises depositing an aluminum nitride layer.

16. The method of claim 11 further comprising, before the etch stop layer is formed, forming a metal cap over the first conductive feature, wherein the metal cap has an additional amorphous structure.

17. The method of claim 16 , wherein the forming the metal cap comprises forming a cobalt nitride layer.

18. A method comprising:

performing a treatment process on a first conductive feature using a nitrogen-containing process gas;

conducting a cobalt-containing process gas to the first conductive feature that has been treated in the treatment process to form a cobalt nitride layer, wherein the cobalt nitride layer comprises a polycrystalline structure;

converting the cobalt nitride layer as an amorphous layer;

forming an etch stop layer over the cobalt nitride layer;

forming a dielectric layer over the etch stop layer; and

forming a conductive feature in the dielectric layer, wherein the conductive feature contacts the cobalt nitride layer.

19. The method of claim 18 , wherein the cobalt-containing process gas comprises an organic gas.

20. The method of claim 18 , wherein the etch stop layer is formed as an additional amorphous layer.