Method of etching extreme ultraviolet light (EUV) photomasks

1. A method of etching an extreme ultraviolet photomask, comprising:

providing a photomask comprising, in order, a substrate, a multi-material layer, a capping layer, and a multi-layer absorber layer, the multilayer absorber layer comprising a self-mask layer disposed over a bulk absorber layer, wherein the self-mask layer comprises tantalum and oxygen and the bulk absorber layer comprises tantalum and essentially no oxygen;

etching the self-mask layer using a first etch process; and

etching the bulk absorber layer using a second etch process different than the first, wherein the etch rate of the bulk absorber layer is greater than the etch rate of the self-mask layer during the second etch process.

2. The method of claim 1 , further comprising:

depositing and patterning a photoresist layer atop the self-mask layer prior to etching the self-mask layer.

3. The method of claim 2 , wherein the step of depositing and patterning a photoresist layer further comprises:

depositing and patterning a photoresist layer to a thickness of between about 100-1000 nm.

4. The method of claim 1 , wherein the second etch process maintains a selectivity for the bulk absorber layer over the self-mask layer of at least 10.

5. The method of claim 1 , wherein the self mask layer comprises one of TaSiON, TaBO, or TaON.

6. The method of claim 1 , wherein the bulk absorber layer comprises one of TaSi, TaBN, or TaN.

7. The method of claim 1 , wherein the self-mask layer comprises TaSiON and the bulk absorber layer comprises TaSi.

8. The method of claim 1 , wherein the self-mask layer comprises TaBO and the bulk absorber layer comprises TaBN.

9. The method of claim 1 , wherein the self-mask layer comprises TaON and the bulk absorber layer comprises TaN.

10. The method of claim 1 , wherein the first etch process comprises:

etching the self-mask layer with a process gas comprising at least one of a fluorine containing gas, carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).

11. The method of claim 1 , wherein the first etch process comprises:

etching the self-mask layer with a process gas comprising at least one of trifluoromethane (CHF 3 ), carbon tetrafluoride (CF 4 ), sulfur hexafluoride (SF 6 ), carbon hexafluoride (C 2 F 6 ), carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).

12. The method of claim 1 , wherein the second etch process comprises:

etching the bulk absorber layer with at least one chlorine containing process gas.

13. The method of claim 1 , wherein the second etch process comprises:

etching the bulk absorber layer with a process gas comprising at least one of chlorine (Cl 2 ), carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).

14. The method of claim 1 , wherein the substrate comprises quartz, the multi-material layer comprises molybdenum and silicon, and the capping layer comprises zirconium and silicon.

15. The method of claim 1 , wherein the thickness of the capping layer and the multi-material absorber layer is between about 70 and 130 nm.

16. The method of claim 15 , wherein the thickness of the capping layer and the multi-material absorber layer is about 100 nm.

17. The method of claim 1 , wherein the bulk absorber layer is between about 80-85 percent of the thickness of the multi-layer absorber layer.

18. The method of claim 1 , wherein the self-mask layer is between about 15-20 percent of the thickness of the multi-layer absorber layer.

19. The method of claim 1 , wherein the thickness of the opaque multi-layer absorber layer is between 40-100 nm.

20. A method for creating an image on a blank extreme ultraviolet photomask comprising a photoresist layer, an opaque layer underlying the photoresist layer having an anti-reflective sub-layer and a bulk sub-layer, a capping layer, an EUV reflective multilayer, and a substrate, the method comprising:

creating a patterned image in the photoresist layer;

removing portions of the photoresist layer that do not correspond to the patterned image thereby exposing portions of the anti-reflective sub-layer of the opaque layer not corresponding to the patterned image;

removing the exposed portions of the anti-reflective sub-layer that do not correspond to the patterned image using a first etch process, thereby exposing portions of the bulk sub-layer not corresponding to the patterned image;

removing the exposed portions of the bulk sub-layer underlying the anti-reflective sub-layer that do not correspond to the patterned image using a second etch process having a bulk sub-layer removal rate that is at least 10 time greater than an anti-reflective sub-layer removal rate, thereby exposing portions of the capping layer that do not correspond to the patterned image; and

removing the photoresist layer.

21. The method of claim 20 , wherein the anti-reflective sub-layer comprises one of TaSiON, TaBO, or TaON.

22. The method of claim 20 , wherein the bulk sub-layer comprises one of TaSi, TaBN, or TaN.

23. The method of claim 20 , wherein removing the exposed portions of the anti-reflective sub-layer comprises:

etching the anti-reflective sub-layer with a process gas comprising at least one of a fluorine containing gas, carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).

24. The method of claim 20 , wherein removing the exposed portions of the anti-reflective sub-layer comprises:

etching the anti-reflective sub-layer with a process gas comprising at least one of trifluoromethane (CHF 3 ), carbon tetrafluoride (CF 4 ), sulfur hexafluoride (SF 6 ), carbon hexafluoride (C 2 F 6 ), carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).

25. The method of claim 20 , wherein removing the exposed portions of the bulk sub-layer comprises:

etching the bulk sub-layer with a process gas comprising at least one chlorine containing gas.

26. The method of claim 20 , wherein removing the exposed portions of the bulk sub-layer comprises:

etching the bulk sub-layer with a process gas comprising at least one of chlorine (Cl 2 ), carbon tetrachloride (CCl 4 ), or hydrogen chloride (HCl).