Self-aligned via structures with barrier layers

1. An interconnect structure comprising:

a conductive line feature over a substrate;

a conductive etch stop layer disposed directly on the conductive line feature, the conductive etch stop layer being electrically conductive;

a contact via disposed directly on the conductive etch stop layer; and

a barrier layer disposed along a sidewall of the conductive line feature, a sidewall of the conductive etch stop layer, and a sidewall of the contact via,

wherein a composition of the conductive line feature is the same as a composition of the contact via.

2. The interconnect structure of claim 1 , wherein a composition of the conductive etch stop layer is different from the composition of the conductive line feature.

3. The interconnect structure of claim 1 ,

wherein the contact via includes a first end away from the substrate and a second end closer to the substrate than the first end,

wherein a width of the first end is substantially identical to a width of the second end.

4. The interconnect structure of claim 1 , wherein the sidewall of the contact via is flush with the sidewall of the conductive etch stop layer.

5. The interconnect structure of claim 4 ,

wherein the sidewall of the conductive line feature is flush with the sidewall of the conductive etch stop layer,

wherein the barrier layer extends continuously along the sidewall of the conductive line feature, the sidewall of the conductive etch stop layer, and the sidewall of the contact via.

6. The interconnect structure of claim 1 ,

wherein a first portion of the conductive etch stop layer is disposed between the conductive line feature and the contact via,

wherein a second portion of the conductive etch stop layer is not disposed between the conductive line feature and the contact via,

wherein a portion of the barrier layer is disposed over the second portion.

7. The interconnect structure of claim 1 , further comprising a glue layer between the conductive line feature and the substrate, wherein the barrier layer extends into the substrate below the glue layer.

8. The interconnect structure of claim 1 , wherein the barrier layer comprises metal nitride.

9. An interconnect structure comprising:

a first conductive line feature over a substrate;

a second conductive line feature over the substrate;

a conductive etch stop layer over the first and second conductive line features;

a first contact via over a first portion of the conductive etch stop layer over the first conductive line feature;

a second contact via over a second portion of the conductive etch stop layer over the second conductive line feature; and

a barrier layer disposed along a sidewall of the first conductive line feature, a sidewall of the conductive etch stop layer, and a sidewall of the first contact via,

wherein a sidewall of the first contact via is flush with a sidewall of the first conductive line feature,

wherein a sidewall of the second portion of the conductive etch stop layer is flush with a sidewall of the second conductive line feature.

10. The interconnect structure of claim 9 ,

wherein the first and second conductive line features comprise ruthenium, copper, cobalt, aluminum, or a combination thereof,

wherein the conductive etch stop layer comprises tungsten, tantalum, or a combination thereof.

11. The interconnect structure of claim 9 ,

wherein the first contact via includes a first end away from the substrate and a second end closer to the substrate than the first end,

wherein a width of the first end is substantially identical to a width of the second end.

12. The interconnect structure of claim 9 ,

wherein the barrier layer extends continuously along the sidewall of the first conductive line feature, the sidewall of the first portion of the conductive etch stop layer, and the sidewall of the first contact via.

13. The interconnect structure of claim 9 , wherein a portion of the barrier layer is disposed over the second portion of the conductive etch stop layer.

14. The interconnect structure of claim 9 , further comprising a glue layer between the first conductive line feature and the substrate, wherein the barrier layer extends into the substrate below the glue layer.

15. The interconnect structure of claim 9 , wherein the barrier layer comprises nitrogen.

16. A method comprising:

depositing a layer stack over a substrate, wherein the layer stack comprises:

a first metal layer,

a conductive etch stop layer disposed directly on the first metal layer,

wherein the conductive etch stop layer comprises a metal,

a second metal layer disposed directly on the conductive etch stop layer, and

a cap layer over the second metal layer; and

patterning the layer stack to form conductive line features out of the first metal layer and contact vias out of the second metal layer,

wherein a composition of the first metal layer is the same as a composition of the second metal layer.

17. The method of claim 16 , wherein the layer stack further comprises:

a first glue layer between the first metal layer and the substrate; and

a second glue layer between the second metal layer and the cap layer.

18. The method of claim 16 , wherein the patterning of the layer stack comprises:

etching the layer stack to form first openings along layer stack features;

depositing a protection layer over the layer stack features;

depositing a hard mask layer over the layer stack features;

patterning the hard mask layer to form second openings;

depositing a reverse material in the second openings; and

patterning the layer stack features using the reverse material as an etch mask.

19. The method of claim 16 , further comprising depositing a barrier layer over the conductive line features and the contact vias.

20. The method of claim 19 ,

wherein a plurality of the contact vias is disposed over a plurality of the conductive line features,

wherein the barrier layer extends from sidewalls of the plurality of the contact vias to sidewalls of the plurality of the conductive line features.