Patent Number: 
Section: claims

1. Reflective optical element having an optically effective surface and comprising:an element substrate;a reflection layer system;at least one deformation reduction layer which, upon the optically effective surface being irradiated with electromagnetic radiation, reduces a maximum deformation level of the reflection layer system in comparison with an analogous construction of a reflective optical element without the deformation reduction layer; andan intermediate layer arranged between the reflection layer system and the deformation reduction layer and configured to block transfer of surface roughnesses to the reflection layer system,wherein the reflection layer system comprises at least one layer composed of a first material having a first coefficient of thermal expansion, and the at least one deformation reduction layer comprises a second material having a second coefficient of thermal expansion, and wherein the first and the second coefficients of thermal expansions have mutually opposite signs. 2. Reflective optical element according to claim 1, wherein the first material comprises at least one of zirconium (Zr), yttrium (Y), molybdenum (Mo), niobium (Nb), silicon (Si), germanium (Ge), rhodium (Rh), ruthenium (Ru), ruthenium dioxide (RuO2) and ruthenium-silicon (RuSi). 3. Reflective optical element according to claim 1, wherein the second material is selected from the group consisting essentially of ZrMo2O8, ZrW2O8, HfMo2O8, HfW2O8, Zr2(MoO4)3, Zr2(WO4)3, Hf2(MoO4)3, Hf2(WO4)3, ScF3, ZnC2N2, ZnF2, Y2W3O12 and BiNiO3. 4. Reflective optical element according to claim 1, wherein the intermediate layer comprises at least one of quartz and silicon (Si). 5. Reflective optical element according to claim 1, wherein the intermediate layer is unprocessed. 6. Reflective optical element according to claim 1, wherein the intermediate layer is mechanically processed or ion beam figured. 7. Reflective optical element according to claim 1 and configured for an operating wavelength of less than 30 nm. 8. Reflective optical element according to claim 1, configured as a mirror for a microlithographic projection exposure apparatus or a mask inspection apparatus. 9. Reflective optical element according to claim 1, configured as a reticle for a microlithographic projection exposure apparatus. 10. Optical system of a microlithographic projection exposure apparatus, comprising at least one reflective optical element according to claim 1 and configured into an illumination device or a projection lens of the projection exposure apparatus. 11. Optical system of a mask inspection apparatus, comprising at least one reflective optical element according to claim 1 and configured into an illumination device or an inspection lens of the mask inspection apparatus. 12. Microlithographic projection exposure apparatus comprising an illumination device and a projection lens, wherein the projection exposure apparatus comprises a reflective optical element according to claim 1 configured into the illumination device or the projection lens. 13. Mask inspection apparatus comprising an illumination device and an inspection lens, wherein the mask inspection apparatus comprises a reflective optical element according to claim 1 configured into the illumination device or the inspection lens. 14. Reflective optical element having an optically effective surface and comprising:an element substrate;a reflection layer system;at least one deformation reduction layer which, upon the optically effective surface being irradiated with electromagnetic radiation, reduces a maximum deformation level of the reflection layer system in comparison with an analogous construction of a reflective optical element without the deformation reduction layer; andan intermediate layer arranged between the reflection layer system and the deformation reduction layer and configured to block transfer of surface roughnesses to the reflection layer system,wherein an effective volume change ΔVeff of an arrangement comprising the reflection layer system and the deformation reduction layer that results from a heating of the optically effective surface by a predetermined temperature difference is a maximum of 90% of a volume change V1 of the reflection layer system alone that results from the heating. 15. Reflective optical element according to claim 14, wherein the effective volume change ΔVeff of the arrangement is a maximum of 90% of the volume change V1 for a heating of the optically effective surface (by a temperature difference of at least 1K. 16. Reflective optical element having an optically effective surface and comprising:an element substrate;a reflection layer system; andat least one deformation reduction layer which, upon the optically effective surface being irradiated with electromagnetic radiation, reduces a maximum deformation level of the reflection layer system in comparison with an analogous construction of a reflective optical element without the deformation reduction layer;wherein the at least one deformation reduction layer comprises a heat distribution layer at a location facing the element substrate, and wherein the heat distribution layer has a thermal conductivity that is greater than a thermal conductivity of the element substrate alone. 17. Reflective optical element according to claim 16, wherein the heat distribution layer has a thermal conductivity of at least 100 W/mK. 18. Reflective optical element according to claim 16, wherein the heat distribution layer comprises at least one material selected from the group consisting essentially of graphite, aluminium (Al), silver (Ag), gold (Au), copper (Cu) and ZrW2O8. 19. Reflective optical element according to claim 16, wherein a heat insulation layer configured to delay entry of heat into the element substrate is arranged between the element substrate and one of the reflection layer system and the deformation reduction layer. 20. Reflective optical element according to claim 19, wherein the heat insulation layer comprises quartz. 21. Reflective optical element according to claim 16, further comprising:an intermediate layer arranged between the reflection layer system and the deformation reduction layer and configured to block transfer of surface roughnesses to the reflection layer system.