Self-forming barrier for use in air gap formation

1. An etch back air gap (EBAG) process, comprising:

forming an initial structure comprising a dielectric layer disposed on a substrate and a liner disposed to line a trench defined in the dielectric layer;

impregnating a metallic interconnect material with dopant material;

filling a remainder of the trench with the impregnated metallic interconnect material to form an intermediate structure; and

annealing the intermediate structure to drive the dopant material out of the impregnated metallic interconnect material and through the liner to thereby form, at an exterior of the liner, a self-forming layer comprising a chemical-attack and plasma-attack immune material.

2. The EBAG process according to claim 1 , wherein the dopant material comprise manganese (Mn).

3. The EBAG process according to claim 1 , further comprising prior to annealing:

exposing the intermediate structure to air;

depositing a removable layer over the dielectric layer, the liner and the impregnated metallic interconnect material; and

depositing a hard mask over the removable layer.

4. The EBAG process according to claim 1 , wherein the annealing comprises timed, controlled heating of the intermediate structure.

5. The EBAG process according to claim 4 , wherein the timed, controlled heating comprises heating the intermediate structure to a temperature of approximately 400° C. for approximately one hour.

6. The EBAG process according to claim 1 , further comprising:

applying a litho-stack to the intermediate structure;

pattern transferring to expose a portion of the intermediate structure;

removing the dielectric layer in the portion of the intermediate structure; and

applying a dielectric capping stack to the intermediate structure.

7. The EBAG process according to claim 6 , wherein the removing comprises damaging and etching the dielectric layer in the portion of the intermediate structure.

8. The EBAG process according to claim 3 , further comprising depositing a cap over the impregnated metallic interconnect material, the cap comprising tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru).

9. The EBAG process according to claim 1 , further comprising

prior to the annealing, depositing a removable layer and a hard mask over the impregnated metallic interconnect material.

10. The EBAG process according to claim 1 , wherein the liner comprises tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru).

11. The EBAG process according to claim 1 , further comprising

prior to the annealing, depositing a removable layer and a hard mask over and directly onto the impregnated metallic interconnect material and wherein the liner comprises tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru).

12. An etch back air gap (EBAG) process, comprising:

forming an initial structure comprising a dielectric layer disposed on a substrate and formed to define a trench;

lining the trench with dopant material;

lining the dopant material with an additional liner; and

filling a remainder of the trench with metallic interconnect material to form an intermediate structure,

wherein the lining of the trench with the dopant material comprises annealing of the intermediate structure to drive the dopant material through the additional liner to thereby form, at an exterior of the additional liner, a self-forming layer comprising a chemical-attack and plasma-attack immune material.

13. The EBAG process according to claim 12 , wherein the dopant material comprise manganese (Mn) and the additional liner comprises tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru).

14. The EBAG process according to claim 12 , further comprising:

planarizing an upper surface of the intermediate structure;

applying a litho-stack to the intermediate structure;

pattern transferring to expose a portion of the intermediate structure;

removing the dielectric layer in the portion of the intermediate structure; and

applying a dielectric capping stack to the intermediate structure.

15. An etch back air gap (EBAG) process, comprising:

forming an initial structure comprising a dielectric layer disposed on a substrate and formed to define a trench;

lining the trench with a liner;

lining the liner with material dopant;

filling a remainder of the trench with metallic interconnect material to form an intermediate structure; and

annealing of the intermediate structure to drive the dopant material through the liner to thereby form, at an exterior of the liner, a self-forming layer comprising a chemical-attack and plasma-attack immune material.

16. The EBAG process according to claim 15 , wherein the dopant material comprise manganese (Mn) and the liner comprises tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru).

17. The EBAG process according to claim 15 , wherein:

the lining of the trench comprises chemical vapor deposition (CVD) of tantalum (Ta), tantalum nitride (TaN), cobalt (Co) or ruthenium (Ru), and

the lining of the liner comprises atomic layer deposition (ALD) or CVD processing of manganese nitride (MnN).

18. The EBAG process according to claim 15 , wherein the annealing comprises heating the intermediate structure to a temperature of about 400° C. for about one hour.

19. The EBAG process according to claim 15 , further comprising:

planarizing an upper surface of the intermediate structure;

applying a litho-stack to the intermediate structure;

pattern transferring to expose a portion of the intermediate structure;

removing the dielectric layer in the portion of the intermediate structure; and

applying a dielectric capping stack to the intermediate structure.

20. The EBAG process according to claim 15 , wherein the dopant material comprise manganese (Mn).