Structure and method for reflective-type mask

1. A reflective mask, comprising:

a substrate;

a reflective multilayer formed on the substrate;

an absorber layer formed on the reflective multilayer, wherein the absorber layer is patterned to have openings according to an integrated circuit layout; and

a protection layer formed over the reflective multilayer within the openings.

2. The reflective mask of claim 1 , wherein the protection layer is of a material having hardness greater than about 8.

3. The reflective mask of claim 1 , wherein the protection layer has a refractive index greater than about 0.95 and an extinction coefficient less than 0.005.

4. The reflective mask of claim 1 , wherein the protection layer includes silicon carbide.

5. The reflective mask of claim 1 , wherein the protection layer includes a Ru alloy selected from the group consisting of YRu, ZrRu, CrRu, RuCo, RuNi, HfRu, RuGe, and combination thereof.

6. The reflective mask of claim 1 , wherein the protection layer includes an yttrium (Y) layer.

7. The reflective mask of claim 1 , wherein the substrate includes a low thermal expansion material (LTEM).

8. The reflective mask of claim 1 , wherein the reflective multilayer includes a plurality of alternating molybdenum-silicon (Mo/Si) films.

9. The reflective mask of claim 1 , wherein the reflective multilayer includes a plurality of alternating molybdenum-beryllium (Mo/Be) films.

10. The reflective mask of claim 1 , wherein the absorber layer includes tantalum boron nitride (TaBN).

11. The reflective mask of claim 1 , wherein the protection layer is further formed on the absorber layer.

12. A reflective mask, comprising:

a substrate;

a reflective multilayer formed on the substrate;

a capping layer of a first material formed on the reflective multilayer;

an absorber layer formed on the capping layer; and

a protection layer of a second material formed on the absorber layer, wherein the absorber layer and the protection layer are both patterned according to an integrated circuit layout, and wherein one of the first and second materials has hardness greater than about 8.

13. The reflective mask of claim 12 , wherein the first and second materials are the same.

14. The reflective mask of claim 12 , wherein one of the first and second materials has a cleaning durability greater than that of ruthenium (Ru);

a refractive index greater than about 0.95; and

an extinction coefficient less than 0.005.

15. The reflective mask of claim 12 , wherein one of the first and second materials includes a Ru alloy selected from the group consisting of YRu, ZrRu, CrRu, RuCo, RuNi, HfRu, RuGe, and combination thereof.

16. The reflective mask of claim 12 , wherein one of the first and second materials includes one of silicon carbide and yttrium (Y).

17. A method for forming a reflective mask for photolithography, comprising:

providing a substrate;

forming a reflective multilayer on the substrate;

forming an absorber layer over the reflective multilayer;

patterning the absorber layer to have a plurality of openings; and

one of following two operations:

before the forming of the absorber layer, forming a capping layer over the reflective multilayer, wherein the capping layer has hardness greater than about 8; and

after the patterning of the absorber layer, forming a first protection layer in the openings.

18. The method of claim 17 , further comprising, before the patterning of the absorber layer:

forming a second protection layer over the absorber layer, wherein the patterning of the absorber layer also patterns the second protection layer.

19. The method of claim 17 , wherein the first protection layer has hardness greater than about 8.

20. The method of claim 17 , wherein the capping layer and the first protection layer are of the same material that has:

a cleaning durability greater than that of ruthenium (Ru);

a refractive index greater than about 0.95; and

an extinction coefficient less than 0.005.