Reflective mask blank for EUV lithography and process for its production, as well as substrate with reflective layer for such mask blank and process for its production

1. A substrate with reflective layer for EUV lithography (EUVL) having a reflective layer for reflecting EUV light formed on a substrate,

wherein the reflective layer is a multilayer reflective film having a low refractive index layer and a high refractive index layer alternately stacked plural times,

among the respective layers constituting the multilayer reflective film, at least one layer of at least one pair of adjacent low refractive index layer and high refractive index layer is made to be a reflectivity distribution correction layer, and

the reflectivity distribution correction layer has a thickness distribution which satisfies the following formula (1) in a radial direction from the center of the substrate:

−0.011 x 2 +0.1 x− 100−α≦ y≦− 0.011 x 2 +0.1 x+ 100+α  (1)

wherein x is a location in a radial direction from the center of the substrate represented by the relative value where the center of the film-forming surface on the substrate on which the reflective layer is to be formed, is 0%, and the outer edge at the reflectivity measurement position farthest from the center of the film-forming surface, is 100%; y is the amount of change of the thickness of the reflectivity distribution correction layer represented by the rate of change where the minimum value of the thickness of the reflectivity distribution correction layer is 0%, and the maximum value of the thickness of the reflectivity distribution correction layer is 100%; and α is 25.

2. The substrate with reflective layer for EUVL according to claim 1 , wherein the thickness distribution of the reflectivity distribution correction layer is by the thickness distribution of the low refractive index layer constituting the reflectivity distribution correction layer.

3. The substrate with reflective layer for EUVL according to claim 1 , wherein the thickness distribution of the reflectivity distribution correction layer is by the thickness distribution of the high refractive index layer constituting the reflectivity distribution correction layer.

4. The substrate with reflective layer for EUVL according to claim 1 , wherein the thickness distribution of the reflectivity distribution correction layer is by the total thickness distribution of the low refractive index layer and the high refractive index layer constituting the reflectivity distribution correction layer.

5. A substrate with reflective layer for EUVL having a reflective layer for reflecting EUV light formed on a substrate,

wherein the reflective layer is a multilayer reflective film having a low refractive index layer and a high refractive index layer alternately stacked plural times, and

the change of the peak reflectivity of light in the EUV wavelength region in a radial direction from the center of the substrate, is within 0.18%.

6. The substrate with reflective layer for EUVL according to claim 1 , which has a protective layer for the reflective layer formed on the reflective layer.

7. The substrate with reflective layer for EUVL according to claim 1 , wherein in the multilayer reflective film, the stacked number of bilayer of the low refractive index layer and the high refractive index layer is from 30 to 60, and the reflectivity distribution correction layer is present within a stacked number of bilayer of at most 20 from the uppermost layer of the multilayer reflective film.

8. The substrate with reflective layer for EUVL according to claim 1 , wherein the multilayer reflective film is a Mo/Si multilayer reflective film having a molybdenum (Mo) layer and a silicon (Si) layer alternately stacked plural times.

9. The substrate with reflective layer for EUVL according to claim 5 , which has a protective layer for the reflective layer formed on the reflective layer.

10. The substrate with reflective layer for EUVL according to claim 5 , wherein the multilayer reflective film is a Mo/Si multilayer reflective film having a molybdenum (Mo) layer and a silicon (Si) layer alternately stacked plural times.

11. A process for producing the substrate with reflective layer for EUVL as defined in claim 1 , which comprises forming on the substrate the multilayer reflective film by alternately stacking a low refractive index layer and a high refractive index layer plural times by a sputtering method.

12. A reflective mask blank for EUV lithography (EUVL), which has an absorber layer for absorbing EUV light formed on the multilayer reflective film of the substrate with reflective layer for EUVL as defined in claim 1 .

13. The reflective mask blank for EUVL according to claim 12 , which has a low reflective layer for inspection light to be used for inspection of a mask pattern formed on the absorber layer.

14. A reflective mask for EUV lithography obtained by patterning the reflective mask blank for EUVL as defined in claim 12 .

15. A process for producing the substrate with reflective layer for EUVL as defined in claim 5 , which comprises forming on the substrate the multilayer reflective film by alternately stacking a low refractive index layer and a high refractive index layer plural times by a sputtering method.

16. A reflective mask blank for EUV lithography (EUVL), which has an absorber layer for absorbing EUV light formed on the multilayer reflective film of the substrate with reflective layer for EUVL as defined in claim 5 .

17. The reflective mask blank for EUVL according to claim 16 , which has a low reflective layer for inspection light to be used for inspection of a mask pattern formed on the absorber layer.

18. A reflective mask for EUV lithography obtained by patterning the reflective mask blank for EUVL as defined in claim 16 .