Patent Number: 
Section: claims

1. An illumination optical unit, comprising:a pupil facet mirror comprising a multiplicity of facets having a form; anda diaphragm comprising first and second regions,wherein:the illumination optical unit is configured to illuminate an object field imageable via an imaging optical unit with radiation from an EUV radiation source;the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a discrete symmetry group in the diaphragm plane;the diaphragm is in a region of an intermediate focal plane of the illumination optical unit; andthe at least one region has a rectangular form with an aspect ratio corresponding exactly to an aspect ratio of the facets of the pupil facet mirror. 2. The illumination optical unit of claim 1, wherein the first region is marginally surrounded completely by the second region. 3. An illumination system, comprising:an EUV radiation source; andan illumination optical unit configured to illuminate an object field imageable via an imaging optical unit with radiation from the EUV radiation source, the illumination optical unit comprising:a pupil facet mirror comprising a multiplicity of facets having a form; anda diaphragm comprising first and second regions,wherein:the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a discrete symmetry group in the diaphragm plane,the at least one region has a rectangular form with an aspect ratio corresponding exactly to an aspect ratio of the facets of the pupil facet mirror; andthe diaphragm is in a region of an intermediate focal plane of illumination system. 4. The illumination system of claim 3, wherein a vacuum separation is between a source unit comprising the EUV radiation source and the illumination optical unit, and the diaphragm is at a boundary between the source unit and the illumination optical unit. 5. The illumination system of claim 3, wherein the first region is marginally surrounded completely by the second region. 6. An apparatus, comprising:an illumination system, comprising:an EUV radiation source; andan illumination optical unit, comprising:a pupil facet mirror comprising a multiplicity of facets having a form; anda diaphragm comprising first and second regions; andan imaging optical unit configured to image the object field into an image field,wherein:the illumination optical unit configured to illuminate the object field;the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a discrete symmetry group in the diaphragm plane;the at least one region has rectangular form with an aspect ratio corresponding exactly to an aspect ratio of the facets of the pupil facet mirror;the diaphragm is in a region of an intermediate focal plane of the illumination system; andthe apparatus is an EUV projection exposure apparatus. 7. The apparatus of claim 6, wherein a vacuum separation is between a source unit comprising the EUV radiation source and the illumination optical unit, and the diaphragm is at a boundary between the source unit and the illumination optical unit. 8. A method of using an EUV projection exposure apparatus which comprises an illumination system and an imaging optical unit, the method comprising:using the illumination system to illuminate a reticle; andusing the imaging optical unit to project a section of the reticle onto a light-sensitive material,wherein the EUV projection exposure apparatus is an EUV projection exposure apparatus of claim 6. 9. The apparatus of claim 6, wherein the first region is marginally surrounded completely by the second region. 10. An apparatus, comprising:an illumination optical unit, comprising:a pupil facet mirror comprising a multiplicity of facets having a form; anda diaphragm comprising first and second regions; andan imaging optical unit configured to image the object field into an image field,wherein:the illumination optical unit is configured to illuminate the object field imageable via an imaging optical unit with radiation from an EUV radiation source;the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a discrete symmetry group in the diaphragm plane;the diaphragm is in a region of an intermediate focal plane of the illumination optical unit;the at least one region has a rectangular form with an aspect ratio corresponding exactly to an aspect ratio of the facets of the pupil facet mirror; andthe apparatus is an EUV projection exposure apparatus. 11. The apparatus of claim 10, wherein a vacuum separation is between a source unit comprising the EUV radiation source and the illumination optical unit, and the diaphragm is at a boundary between the source unit and the illumination optical unit. 12. The apparatus of claim 10, wherein the first region is marginally surrounded completely by the second region. 13. A method of using an EUV projection exposure apparatus which comprises an illumination system and an imaging optical unit, the method comprising:using the illumination system to illuminate a reticle; andusing the imaging optical unit to project a section of the reticle onto a light-sensitive material,wherein the EUV projection exposure apparatus is an EUV projection exposure apparatus of claim 10. 14. An illumination optical unit, comprising:a pupil facet mirror comprising a multiplicity of facets having a form; anda diaphragm comprising first and second regions,wherein:the illumination optical unit is configured to illuminate an object field imageable via an imaging optical unit with radiation from an EUV radiation source;the first region is transmissive to the EUV radiation;the second region is opaque to the EUV radiation;the first and second regions define a diaphragm plane;at least one region selected from the group consisting of the first region and the second region has a two-fold but not a four-fold rotational symmetry in the diaphragm plane;the at least one region has a form adapted to the form of the facets of the pupil facet mirror; andthe at least one region has a polygonal form. 15. The illumination optical unit of claim 14, wherein the first region is marginally surrounded completely by the second region. 16. The illumination optical unit of claim 14, wherein the diaphragm has the same symmetry properties as the facets of the pupil facet mirror. 17. An illumination system, comprising:an EUV radiation source; andthe illumination optical unit of claim 14. 18. The illumination system of claim 17, wherein the diaphragm is in a region of an intermediate focal plane of the illumination system. 19. The illumination system of claim 17, wherein:the illumination system has a vacuum separation between a source unit and the illumination optical unit;the source unit comprises the EUV radiation source; andthe diaphragm is at a boundary between the source unit and the illumination optical unit. 20. An apparatus comprising:an illumination system comprising:an EUV radiation source; andthe illumination optical unit of claim 14,wherein the apparatus is an EUV projection exposure apparatus. 21. The apparatus of claim 20, wherein the diaphragm is in a region of an intermediate focal plane of the illumination system. 22. The apparatus of claim 20, wherein:the illumination system has a vacuum separation between a source unit and the illumination optical unit;the source unit comprises the EUV radiation source; andthe diaphragm is at a boundary between the source unit and the illumination optical unit. 23. A method of using an EUV projection disposure apparatus comprising an illumination system and an imaging optical unit, the method comprising:using the illumination system to illuminate a reticle; andusing the imaging optical unit to project a section of the reticle onto a light-sensitive material,wherein the illumination system comprises an EUV radiation source and the illumination optical unit of claim 14. 24. The method of claim 23, wherein the diaphragm is in a region of an intermediate focal plane of the illumination system. 25. The method of claim 23, wherein:the illumination system has a vacuum separation between a source unit and the illumination optical unit;the source unit comprises the EUV radiation source; andthe diaphragm is at a boundary between the source unit and the illumination optical unit.