Etch stop in a dep-etch-dep process

1. A method of forming a semiconductor device comprising:

depositing a conductive underlying layer in a cavity of a semiconductor device, a surface of the conductive underlying layer in contact with a surface of a source or drain region;

depositing an etch stop layer of titanium aluminum carbide on the conductive underlying layer;

depositing a first layer of metal on the etch stop layer;

etching the first layer of metal with an etchant comprising NF 3 to create an etch-modified surface of the first layer of metal, the etch stop layer of titanium aluminum carbide acting as an etch stop while etching the first layer; and

depositing a second layer of metal on the etch-modified surface of the first layer of metal.

2. The method of claim 1 , wherein the cavity is a trench.

3. The method of claim 2 , wherein the trench is a high aspect ratio trench.

4. The method of claim 1 , wherein the first layer of metal is tungsten.

5. The method of claim 1 , wherein etching is anisotropic etching using a generated plasma under an environment of a nitride containing gas NF 3 .

6. The method of claim 1 , wherein the method further comprises surface treating the etch-modified surface of the first layer of metal with an environment of mixed gases.

7. The method of claim 6 , wherein the underlying layer comprises a multiplicity of layers.

8. The method of claim 1 , wherein the etch stop layer has a thickness of 0.5 to 10 nanometers.

9. A method of making a semiconductor structure comprising:

creating a cavity in a semiconductor device;

depositing an underlying layer in the cavity, a surface of the conductive underlying layer in contact with a surface of a source or drain region;

depositing an etch stop layer of titanium aluminum carbide on the underlying layer;

depositing a first layer of tungsten on the etch stop layer;

etching the first layer of tungsten with an etchant comprising NF 3 to create an etch-modified surface of the first layer of tungsten, the etch stop layer of titanium aluminum carbide acting as an etch stop while etching the first layer; and

depositing a second layer of tungsten on the etch-modified surface of the first layer of tungsten.

10. The method of claim 9 , wherein the cavity is a trench.

11. The method of claim 10 , wherein the trench is a high aspect ratio trench.

12. The method of claim 9 , wherein etching is anisotropic etching using a generated plasma under an environment of a nitride containing gas NF 3 .

13. The method of claim 9 , wherein the method further comprises surface treating the etch-modified surface of the first layer of tungsten with an environment of mixed gases.

14. The method of claim 13 , wherein the underlying layer comprises a multiplicity of layers.

15. The method of claim 9 , wherein the etch stop layer has a thickness of 0.5 to 10 nanometers.

16. A semiconductor device comprising:

a filled feature;

a conductive underlying layer, a surface of the conductive underlying layer in contact with a surface of a source or drain region; and

a metal fill;

wherein the filled feature comprises an etch stop layer comprising a titanium aluminum carbide layer disposed between and in direct contact with the underlying layer and the metal fill; and

wherein the underlying layer comprises titanium, titanium nitride, cobalt, nickel, platinum, nickel platinum titanium, or a combination thereof.

17. The semiconductor device of claim 16 , wherein the metal fill comprises tungsten.

18. The semiconductor device of claim 16 , wherein the filled feature is a high aspect ratio trench.

19. The semiconductor device of claim 16 , wherein the etch stop layer has a thickness of 0.5 to 10 nanometers.