Method of forming interconnect structures

1. A method comprising:

forming a first conductive feature in a first dielectric layer;

forming an etch stop layer over the first dielectric layer;

forming a second dielectric layer over the etch stop layer;

etching the second dielectric layer and the etch stop layer to form an opening, wherein a portion of the etch stop layer is interposed between a bottom of the opening and the first conductive feature;

sputtering the portion of the etch stop layer to extend the opening toward the first conductive feature and form an extended opening, wherein the extended opening exposes the first conductive feature; and

filling the extended opening with a conductive material to form a second conductive feature in the second dielectric layer.

2. The method of claim 1 , wherein forming the etch stop layer comprises depositing a metal-doped aluminum nitride layer over the first dielectric layer.

3. The method of claim 1 , wherein forming the etch stop layer comprises in situ doping the etch stop layer with metal dopants.

4. The method of claim 1 , wherein the sputtering further removes a portion of the second dielectric layer.

5. The method of claim 1 , wherein the sputtering is performed using ions of an inert gas.

6. The method of claim 1 , wherein etching the second dielectric layer and the etch stop layer comprises chemically etching the second dielectric layer and the etch stop layer.

7. The method of claim 1 , wherein a thickness of the portion of the etch stop layer is between about 0.1 Å and about 0.5 Å.

8. A method comprising:

forming a first conductive feature in a first dielectric layer;

depositing an etch stop layer over the first dielectric layer;

depositing a second dielectric layer over the etch stop layer;

depositing a first mask layer over the second dielectric layer;

depositing a second mask layer over the first mask layer;

performing a first patterning process on the second dielectric layer to form an opening in the second dielectric layer, wherein the first mask layer and the second mask layer are used as a combined mask;

removing the second mask layer;

performing a second patterning process on the second dielectric layer and the etch stop layer to extend the opening into the etch stop layer, wherein a bottom of the opening is disposed within the etch stop layer after performing the second patterning process;

performing a sputtering process on the bottom of the opening to expose a portion of the first conductive feature; and

depositing a conductive material into the opening to form a second conductive feature in the second dielectric layer, wherein the second conductive feature is in electrical contact with the first conductive feature.

9. The method of claim 8 , wherein depositing the etch stop layer comprises depositing a metal-doped aluminum nitride layer over the first dielectric layer.

10. The method of claim 9 , wherein depositing the metal-doped aluminum nitride layer comprises:

depositing an aluminum nitride layer over the first dielectric layer; and

in situ doping the aluminum nitride layer with metal dopants.

11. The method of claim 8 , wherein the sputtering process is performed using an inert gas.

12. The method of claim 8 , wherein removing the second mask layer comprises performing a wet etch process on the second mask layer.

13. The method of claim 8 , wherein performing the first patterning process on the second dielectric layer comprises performing an etch process on the second dielectric layer, the etch process chemically etching the second dielectric layer.

14. The method of claim 8 , wherein performing the second patterning process on the second dielectric layer and the etch stop layer comprises performing an etch process on the second dielectric layer and the etch stop layer, the etch process chemically etching the second dielectric layer and the etch stop layer.

15. A method comprising:

forming a metallization layer over a substrate;

depositing a metal-doped aluminum nitride layer over the metallization layer;

depositing a dielectric layer over the metal-doped aluminum nitride layer;

depositing a first mask layer over the dielectric layer;

depositing a second mask layer over the first mask layer;

performing a first etch process on the dielectric layer to form an opening in the dielectric layer, wherein the first mask layer and the second mask layer are used as a combined etch mask, and wherein the opening exposes the metal-doped aluminum nitride layer;

performing a second etch process on the dielectric layer and the metal-doped aluminum nitride layer to extend the opening into the metal-doped aluminum nitride layer, wherein the first mask layer is used as an etch mask, and wherein a portion of the metal-doped aluminum nitride layer is interposed between a bottom of the opening and a top surface of the metallization layer after performing the second etch process;

performing a sputtering process to remove the portion of the metal-doped aluminum nitride layer and expose a conductive feature of the metallization layer; and

filling the opening with a conductive material.

16. The method of claim 15 , wherein the metal-doped aluminum nitride layer is an etch stop layer.

17. The method of claim 15 , wherein depositing the metal-doped aluminum nitride layer comprises:

depositing an aluminum nitride layer over the metallization layer; and

in situ doping the aluminum nitride layer with metal dopants.

18. The method of claim 15 , further comprising, before performing the second etch process, removing the second mask layer.

19. The method of claim 15 , wherein the sputtering process is performed using non-reactive ions.

20. The method of claim 15 , wherein a thickness of the portion of the metal-doped aluminum nitride layer is between about 0.1 Å and about 0.5 Å.