Methods for fabricating integrated circuits with improved contact structures

1. A method for fabricating integrated circuits, the method comprising:

providing a semiconductor substrate disposed with a device therein and/or thereon;

forming a contact structure in electrical contact with the device, wherein the contact structure includes a barrier layer and a plug metal overlying the barrier layer;

forming a hardmask overlying the contact structure;

performing an etch to form a via opening through the hardmask and to expose the barrier layer and the plug metal;

after performing the etch to form the via opening through the hardmask, forming a contact cap on the fill metal and barrier layer;

removing a remaining portion of the hardmask with a wet etchant, wherein the contact cap inhibits the wet etchant from etching the barrier layer; and

filling the via opening with a conductive material to form an interconnect to the contact structure.

2. The method of claim 1 wherein forming a hardmask over the contact structure comprises forming a titanium nitride hardmask over the contact structure.

3. The method of claim 1 further comprising depositing dielectric material over the semiconductor substrate, wherein forming a contact structure comprises:

etching a contact opening through the dielectric material;

depositing a barrier material in the contact opening to form the barrier layer; and

depositing a fill metal over the barrier layer to form the plug metal filling the contact opening.

4. The method of claim 1 further comprising:

depositing a dielectric material over the contact structure, wherein performing the etch to form the via opening comprises etching the dielectric material to form the via opening therethrough, wherein forming the contact cap on the fill metal and barrier layer comprises selectively depositing tungsten in the via opening on the fill metal and laterally growing the tungsten to cover the barrier layer.

5. The method of claim 1 wherein removing a remaining portion of the hardmask with a wet etchant comprises removing a remaining portion of the hardmask with an etchant including an oxidizer, a pH adjustor and/or a tungsten corrosion inhibitor.

6. The method of claim 1 further comprising:

depositing a dielectric material over the contact structure, wherein performing the etch to form the via opening comprises etching the dielectric material to form the via opening therethrough, wherein forming the contact cap on the fill metal and barrier layer comprises selectively depositing tungsten in the via opening on the fill metal and laterally growing the tungsten into contact with the dielectric material to cover the barrier layer.

7. The method of claim 1 wherein forming a contact structure in electrical contact with the device comprises depositing fluorine free tungsten (FFW), tungsten nitride, or tungsten carbide to form the barrier layer.

8. The method of claim 7 wherein removing a remaining portion of the hardmask with a wet etchant comprises removing a remaining portion of the hardmask with a wet etchant selective to titanium nitride over FFW, such that the contact structure is configured to inhibit the wet etchant from etching the barrier layer.

9. The method of claim 7 further comprising depositing dielectric material over the semiconductor substrate, wherein forming a contact structure comprises:

etching a contact opening through the dielectric material; and

exposing the substrate to a non-halogen organometallic tungsten precursor and a reducing agent to deposit a tungsten-rich film in the contact opening, wherein the tungsten-rich film is the barrier layer.

10. The method of claim 9 wherein forming a contact structure further comprises substantially filling the contact opening with tungsten to form the plug metal.

11. The method of claim 7 further comprising depositing dielectric material over the semiconductor substrate, wherein forming a contact structure comprises:

etching a contact opening through the dielectric material;

exposing the semiconductor substrate to a non-halogen organometallic tungsten precursor and a reducing agent to deposit a tungsten-rich film in the contact opening;

exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film, wherein the tungsten-rich film and the one or more tungsten layers form the barrier layer.

12. The method of claim 11 wherein forming a contact structure further comprises substantially filling the contact opening with tungsten to form the plug metal.

13. A method for fabricating integrated circuits, the method comprising:

providing a semiconductor substrate disposed with a device therein and/or thereon;

forming a contact structure in electrical contact with the device, wherein the contact structure includes a barrier layer and a plug metal;

forming a dielectric layer and a hardmask over the contact structure;

etching the hardmask and dielectric layer to form a via opening through the hardmask and dielectric layer and to expose the contact structure;

forming a contact cap in the via opening over the plug metal and the barrier layer;

removing a remaining portion of the hardmask with a wet etchant, wherein the contact cap inhibits the wet etchant from etching the barrier layer; and

filling the via opening with a conductive material to form an interconnect to the contact structure.

14. The method of claim 13 wherein forming the contact cap on the barrier layer and the plug metal comprises selectively growing the contact cap from the plug metal into contact with the dielectric layer to cover the barrier layer.

15. The method of claim 13 further comprising depositing dielectric material over the semiconductor substrate, wherein forming a contact structure comprises:

etching a contact opening through the dielectric material;

depositing a barrier material in the contact opening to form the barrier layer; and

depositing a fill metal over the barrier layer to form the plug metal, wherein the plug metal fills the contact opening.

16. The method of claim 13 wherein forming the contact cap in the via opening over the fill metal and barrier layer comprises selectively depositing tungsten on the fill metal and covering the barrier layer by lateral growth of the tungsten.

17. A method for fabricating integrated circuits, the method comprising:

providing a semiconductor substrate disposed with a device therein and/or thereon;

forming a contact structure in electrical contact with the device, wherein forming the contact structure includes depositing fluorine free tungsten (FFW), tungsten nitride, or tungsten carbide to form a barrier layer and forming a plug metal overlying the barrier layer;

forming a hardmask overlying the contact structure;

performing an etch to form a via opening through the hardmask and to expose the barrier layer and the plug metal;

removing a remaining portion of the hardmask with a wet etchant, wherein the contact structure is configured to inhibit the wet etchant from etching the barrier layer; and

filling the via opening with a conductive material to form an interconnect to the contact structure.

18. The method of claim 17 wherein removing a remaining portion of the hardmask with a wet etchant comprises removing a remaining portion of the hardmask with a wet etchant selective to titanium nitride over FFW, such that the contact structure is configured to inhibit the wet etchant from etching the barrier layer.

19. The method of claim 17 wherein forming the contact structure in electrical contact with the device comprises depositing fluorine free tungsten (FFW) to form the barrier layer.

20. The method of claim 17 wherein forming the contact structure in electrical contact with the device comprises depositing tungsten carbide to form the barrier layer.