Film stack including metal hardmask layer for sidewall image transfer fin field effect transistor formation

1. A method for formation of a fin field effect transistor (FinFET) device, the method comprising:

forming a mandrel mask and a large feature (FX) mask on a metal hardmask layer of a film stack, the film stack comprising a silicon on insulator (SOI) layer located underneath the metal hardmask layer and an amorphous carbon layer located on top of the metal hardmask layer, wherein forming the mandrel mask and the FX mask comprises:

etching the amorphous carbon layer to form a plurality of mandrels on the metal hardmask layer;

depositing a sidewall image transfer (SIT) spacer layer over the plurality of mandrels and on the metal hardmask layer;

performing etchback of the SIT spacer layer to expose top surfaces of the plurality of mandrels; and

removing the plurality of mandrels, wherein a portion of the SIT spacer layer that remains on the metal hardmask layer comprises the mandrel mask;

etching the mandrel mask and the FX mask simultaneously into the metal hardmask layer; and

etching the mandrel mask and the FX mask into the SOI layer using the etched metal hardmask layer as a mask.

2. The method of claim 1 , wherein the film stack further comprises:

a buried oxide (BOX) layer located underneath the SOI layer;

a thermal silicon oxide layer located on top of the SOI layer and underneath the metal hardmask layer;

and

a cap layer located on top of the amorphous carbon layer.

3. The method of claim 1 , wherein the SIT spacer layer comprises one of silicon oxide and silicon nitride, and is deposited by conformal deposition.

4. The method of claim 1 , wherein the FX mask is formed on the SIT spacer layer before etchback of the SIT spacer layer is performed, such that a portion of the SIT spacer layer comprises the FX mask.

5. The method of claim 1 , further comprising forming a cut mask over the etched SOI layer after etching the mandrel mask and the FX mask into the SOI layer, wherein the cut mask is configured to remove an unnecessary feature formed by the mandrel mask or the FX mask in the SOI layer.

6. The method of claim 1 , further comprising forming a cut mask on the metal hardmask layer before etching the mandrel mask and the FX mask into the metal hardmask layer, wherein the cut mask is configured to remove a portion of the mandrel mask or the FX mask corresponding to an unnecessary feature.

7. The method of claim 1 , wherein the metal hardmask layer comprises titanium nitride (TiN).

8. The method of claim 2 , wherein the cap layer comprises silicon nitride.

9. The method of claim 2 , wherein the cap layer comprises the same material as the SIT spacer layer, and wherein the cap layer is not removed before deposition of the SIT spacer layer.

10. The method of claim 2 , wherein the cap layer comprises a different material from the SIT spacer layer, and wherein the cap layer is removed before deposition of the SIT spacer layer.

11. The method of claim 2 , wherein the mandrel mask and the FX mask are etched into the thermal silicon oxide layer using the etched metal hardmask layer as a mask before etching the mandrel mask and the FX mask into the SOI layer.

12. A film stack for formation of a fin field effect transistor (FinFET) device, comprising:

a buried oxide (BOX) layer;

a silicon on insulator (SOI) layer located on the BOX layer;

a thermal silicon oxide layer located on top of the SOI layer;

a metal hardmask layer located on top of the thermal silicon oxide layer; and

an amorphous carbon layer located on top of the metal hardmask layer, wherein the amorphous carbon layer comprises a plurality of mandrels corresponding to a mandrel mask located on the metal hardmask layer, and further comprising a sidewall image transfer (SIT) spacer layer located over the plurality of mandrels and the metal hardmask layer.

13. The film stack of claim 12 , wherein the metal hardmask layer comprises titanium nitride (TiN).

14. The film stack of claim 12 , further comprising a cap layer located on top of the amorphous carbon layer.

15. The film stack of claim 12 , wherein the cap layer comprises silicon nitride.

16. The film stack of claim 12 , further comprising a cap layer located on top of the amorphous carbon layer, wherein the cap layer comprises the same material as the SIT spacer layer.

17. The film stack of claim 12 , wherein the SIT spacer layer comprises one of silicon oxide and silicon nitride.

18. The film stack of claim 12 , wherein a portion of the SIT spacer layer comprises a large feature (FX) mask.