Reflective element for mask blank and process for producing reflective element for mask blank

1. A process for producing a reflective element suitable for a mask blank, the process comprising:

(1) forming a reflective layer on a first surface of a substrate,

(2) forming a first protective layer on the reflective layer,

(3) cleaning the substrate to form an exposed part of the reflective layer, wherein the exposed part is not covered with the first protective layer, and

(4) forming a second protective layer on a first surface side of the substrate to cover the exposed part with the second protective layer.

2. The process of claim 1 , wherein the second protective layer has a thickness in a range of 0.3 to 3.0 nm.

3. The process of claim 1 , wherein the second protective layer has a thickness in a range of 0.3 to 0.6 nm.

4. The process of claim 1 , wherein the first protective layer comprises ruthenium (Ru) or a ruthenium compound.

5. The process of claim 1 , wherein the process further comprises:

(5) forming an absorber layer on the first surface side of the substrate after (4), and

(6) optionally forming a low reflective layer on the absorber layer.

6. The process of claim 5 , wherein the process further comprises (6) forming a low reflective layer on the absorber layer.

7. The process of claim 6 , wherein the low reflective layer and the absorber layer comprise tantalum (Ta).

8. The process of claim 5 , wherein the process further comprises (7) etching the absorber layer and, if the low reflective layer is present, the low reflective layer.

9. The process of claim 1 , wherein the first protective layer and the second protective layer are made of the same material.

10. The process of claim 1 , wherein the second protective layer is made of a different material than the first protective layer.

11. The process of claim 8 , wherein

(7) comprises etching with dry etching gas ions, and

the second protective layer is made of a material that has an etching durability higher than an etching durability of the first protective layer,

wherein the etching durability of the material and the etching durability of the first protective layer are with respect to the dry etching gas ions.

12. The process of claim 1 , wherein the reflective layer has a repeating structure of a Mo film and a Si film.

13. A reflective element, comprising:

a substrate having a first surface,

a reflective layer formed on the first surface, and

a protective layer formed on the reflective layer,

wherein the protective layer has a first layer and a second layer, and

the second layer covers an exposed part of the reflective layer where the first layer does not exist.

14. The reflective element of claim 13 , wherein at least a part of the surface on a first layer side of the second layer is an oxide layer.

15. The reflective element of claim 14 , wherein the reflective layer has a repeating structure of a Mo film and a Si film.

16. The reflective element of claim 14 , wherein the first layer comprises ruthenium (Ru) or a ruthenium compound.

17. The reflective element of claim 14 , wherein the second layer is made of a different material than the first layer.

18. The reflective element of claim 14 , wherein the second layer has a thickness in a range of 0.3 to 3.0 nm.

19. The reflective element of claim 14 , wherein the second layer has a thickness in a range of 0.3 to 0.6 nm.

20. The reflective element of claim 14 , further comprising an absorber layer comprising tantalum (Ta), wherein the absorber layer is disposed on the protective layer.

21. The reflective element of claim 14 , further comprising a low reflective layer comprising tantalum nitride (TaN), wherein the low reflective layer is disposed on the absorber layer.