Patent Number: 
Section: claims

1. A reflective optical element, comprising:a substrate;a dielectric layer system; anda metallic coating between the substrate and the dielectric layer system,wherein the dielectric layer system is configured to reflect radiation at an operating wavelength greater than or equal to 150 nm and comprises at least one four-layer sequence of layers, the at least one four-layer sequence of layers comprising:a layer composed of material having a lower refractive index n1 at the operating wavelength,a layer composed of material having a higher refractive index n2 at the operating wavelength,a first layer composed of material having a medium refractive index n3 at the operating wavelength, where n1<n3<n2, anda second layer composed of the material having the medium refractive index n3,wherein the four-layer sequence is (LM1HM2)m or (HM1LM2)m, where L designates the layer composed of material having the lower refractive index n1 at the operating wavelength, H designates the layer composed of material having the higher refractive index n2 at the operating wavelength, M1 designates the first layer composed of material having a refractive index n3 at the operating wavelength, and M2 designates the second layer composed of material having a refractive index n3 at the operating wavelength, and where m designates a number of the four-layer sequences in the dielectric layer system, andwherein the layer (L) composed of material having the lower refractive index n1 is composed of at least one of: aluminum fluoride, cryolite, chiolite, lithium fluoride and magnesium fluoride, the layer (H) composed of material having the higher refractive index n2 is composed of at least one of: neodymium fluoride, gadolinium fluoride, dysprosium fluoride, lanthanum fluoride and aluminum oxide, and the layers (M1, M2) composed of material having the medium refractive index n3 are composed of at least one of: magnesium fluoride, yttrium fluoride and silicon dioxide. 2. The reflective optical element as claimed in claim 1, wherein the layer of the dielectric layer system which is furthest away from the substrate is a layer composed of material having the medium refractive index n3. 3. The reflective optical element as claimed in claim 1, wherein the layer of the dielectric layer system which is second closest to the substrate is composed of material having the medium refractive index n3. 4. The reflective optical element as claimed in claim 1, wherein the metallic coating comprises at least one of: aluminum, an aluminum-silicon alloy, an aluminum-manganese alloy, an aluminum-silicon-manganese alloy, and rhodium. 5. An optical system for a lithography device or a microscopy device comprising a reflective optical element as claimed in claim 1. 6. The reflective optical element as claimed in claim 1, configured for an operating wavelength in a deep ultraviolet (DUV) or vacuum ultraviolet (VUV) wavelength range. 7. A lithography device for an operating wavelength in a DUV or VUV wavelength range comprising a reflective optical element as claimed in claim 1. 8. A microscope device for an operating wavelength in a DUV or VUV wavelength range comprising a reflective optical element as claimed in claim 1. 9. A reflective optical element, comprising:a substrate;a dielectric layer system configured to reflect radiation at an operating wavelength between 240 nm and 300 nm; anda metallic coating between the substrate and the dielectric layer system,wherein the dielectric layer system comprises at least one four-layer sequence of layers, the at least one four-layer sequence of layers comprising:a layer composed of material having a lower refractive index n1 at the operating wavelength,a layer composed of material having a higher refractive index n2 at the operating wavelength,a first layer composed of material having a medium refractive index n3 at the operating wavelength, where n1<n3<n2, anda second layer composed of the material having the medium refractive index n3,wherein the four-layer sequence is (LM1HM2)m or (HM1LM2)m, where L designates the layer composed of material having the lower refractive index n1 at the operating wavelength, H designates the layer composed of material having the higher refractive index n2 at the operating wavelength, M1 designates the first layer composed of material having a refractive index n3 at the operating wavelength, and M2 designates the second layer composed of material having a refractive index n3 at the operating wavelength, and where m designates a number of the four-layer sequences in the dielectric layer system, andwherein the layer (L) composed of material having the lower refractive index n1 is composed of at least one of: aluminum fluoride, cryolite, chiolite, lithium fluoride and magnesium fluoride, the layer (H) composed of material having the higher refractive index n2 is composed of at least one of: yttrium oxide, hafnium oxide, scandium oxide, zirconium oxide, aluminum nitride and synthetic diamond, and the layers (M1, M2) composed of material having the medium refractive index n3 is composed of at least one of: barium fluoride, gadolinium fluoride, lanthanum fluoride, neodymium fluoride, dysprosium fluoride, aluminum oxide, yttrium fluoride, ytterbium fluoride and silicon dioxide. 10. The reflective optical element as claimed in claim 9, wherein the layer of the dielectric layer system which is furthest away from the substrate is a layer composed of material having the medium refractive index n3. 11. The reflective optical element as claimed in claim 9, wherein the layer of the dielectric layer system which is second closest to the substrate is composed of material having the medium refractive index n3. 12. The reflective optical element as claimed in claim 9, wherein the metallic coating comprises at least one of: aluminum, an aluminum-silicon alloy, an aluminum-manganese alloy, an aluminum-silicon-manganese alloy, and rhodium. 13. A lithography device for operating within the 240 nm to 300 nm wavelength range comprising a reflective optical element as claimed in claim 9. 14. A microscope device for operating within the 240 nm to 300 nm wavelength range comprising a reflective optical element as claimed in claim 9. 15. A reflective optical elementa substrate;a dielectric layer system configured to reflect radiation an operating wavelength between 150 nm and 240 nm; anda metallic coating between the substrate and the dielectric layer system,wherein the dielectric layer system comprises at least one four-layer sequence of layers, the at least one four-layer sequence of layers comprising:a layer composed of material having a lower refractive index n1 at the operating wavelength,a layer composed of material having a higher refractive index n2 at the operating wavelength, anda first layer composed of material having a medium refractive index n3 at the operating wavelength, where n1<n3<n2, anda second layer composed of the material having the medium refractive index n3,wherein the four-layer sequence is (LM1HM2)m or (HM1LM2)m, where L designates the layer composed of material having the lower refractive index n1 at the operating wavelength, H designates the layer composed of material having the higher refractive index n2 at the operating wavelength, M1 designates the first layer composed of material having a refractive index n3 at the operating wavelength, M2 designates the second layer composed of material having a refractive index n3 at the operating wavelength, and where m designates a number of the four-layer sequences in the dielectric layer system, andwherein the layer (L) composed of material having the lower refractive index n1 is composed of at least one of: aluminum fluoride, cryolite, chiolite, lithium fluoride and magnesium fluoride, the layer (H) composed of material having the higher refractive index n2 is composed of at least one of: neodymium fluoride, gadolinium fluoride, dysprosium fluoride, lanthanum fluoride and aluminum oxide, and the layers (M1, M2) composed of material having the medium refractive index n3 are composed of at least one of: magnesium fluoride, yttrium fluoride and silicon dioxide. 16. The reflective optical element as claimed in claim 15, wherein the layer of the dielectric layer system which is second closest to the substrate is composed of material having the medium refractive index n3. 17. The reflective optical element as claimed in claim 15, wherein the metallic coating comprises at least one of: aluminum, an aluminum-silicon alloy, an aluminum-manganese alloy, an aluminum-silicon-manganese alloy, and rhodium. 18. A lithography device for operating within the 150 nm and 240 nm wavelength range comprising a reflective optical element as claimed in claim 15. 19. A microscope device for operating within the 150 nm and 240 nm wavelength range comprising a reflective optical element as claimed in claim 15.