Bundle-guiding optical collector for collecting the emission of a radiation source
View Patent ↗A bundle-guiding optical collector collects an emission of a radiation source and forms a radiation bundle from the collected emission. A reflective surface of the collector is the first bundle-forming surface downstream of the radiation source. The reflective surface is formed such that it converts the radiation source into a family of images in a downstream plane. The family of images includes a plurality of radiation source images which are offset to each other in two dimensions (x, y) in a direction perpendicular to the beam direction of the transformed radiation bundle and are arranged relative to each other in a non-rotationally symmetric manner relative to the beam direction of the transformed radiation bundle. The transformed radiation bundle in the downstream plane has a non-rotationally symmetric bundle edge contour relative to the beam direction of the transformed radiation bundle. The result is a collector in which the radiation bundle shape generated by the collector. In other words, the illumination distribution generated by the collector in a defined manner in the plane downstream of the collector has a shape which is freely selectable to the greatest possible extent.
1. An optical system having an illumination field, the optical system comprising:
a bundle-guiding optical collector configured to collect radiation emitted by a radiation source and to form a transformed radiation bundle from a collected source-side radiation bundle, the bundle-guiding optical collector comprising a reflective surface which is a first bundle-forming surface downstream of the radiation source; and
a bundle-guiding optical element upstream of the illumination field along a path of the radiation through the optical system,
wherein:
the reflective surface comprises a plurality of reflective facets that complement each other to provide a total reflector surface;
at least some of the facets have aspheric reflector surfaces;
the reflective surface is configured to convert the radiation into a family of images in a downstream plane;
the family of images includes a plurality of radiation source images offset from each other in two dimensions relative to a beam direction of the transformed radiation bundle;
the family of images is arranged relative to each other in a non-rotationally symmetric manner with respect to the beam direction of the transformed radiation bundle so that the transformed radiation bundle in the downstream plane has a non-rotationally symmetric bundle edge contour relative to the beam direction of the transformed radiation bundle; and
the bundle-guiding optical element is in the downstream plane.
2. The optical system according to claim 1 , wherein the reflective surface is configured so that the bundle edge contour is adapted to a shape of a field to be illuminated.
3. The optical system according to claim 1 , wherein the reflective surface is configured so that the bundle edge contour is adapted to a shape of the bundle-guiding optical element.
4. The optical system according to claim 3 , wherein the bundle-guiding optical element comprises a field facet mirror.
5. The optical system according to claim 1 , wherein the facets form a parquet.
6. The optical system according to claim 1 , wherein at least two of the facets are different surface areas.
7. The optical system according to claim 1 , wherein the facets comprise facets having differently shaped edge contours.
8. The optical system according to claim 1 , wherein the facets are in rows and/or columns, and a height of the rows and/or a width of the columns varies along a course from a first side of the reflective surface to a second side of the reflective surface.
9. The optical system according to claim 1 , wherein at least some of the facets have ellipsoidal reflector surfaces.
10. The optical system according to claim 1 , wherein the reflective surface between the facets is smoothed out so that the reflective surface is continuously differentiable at any point within a boundary of the reflective surface.
11. The optical system according to claim 1 , wherein the reflective surface between the facets is smoothed so that a continuous illumination distribution is obtained within the bundle edge contour.
12. The optical system according to claim 1 , wherein the reflective surface is a freeform surface.
13. The optical system according to claim 1 , wherein segments of the reflective surface and/or the facets are actively deformable or tiltable.
14. The optical system according to claim 1 , wherein a tilting angle of the facets is configured so that imaging errors caused by downstream components are compensated.
15. The optical system according to claim 1 , wherein the non-rotationally symmetric bundle edge contour has at least a two-fold symmetry.
16. An optical system having an illumination field, the optical system comprising:
a bundle-guiding optical collector configured to collect radiation emitted by a radiation source and to form a transformed radiation bundle from a collected source-side radiation bundle, the bundle-guiding optical collector comprising a reflective surface which is a first bundle-forming surface downstream of the radiation source; and
a bundle-guiding optical element upstream of the illumination field along a path of the radiation through the optical system,
wherein:
a collector edge contour of the reflective surface has a shape that is mirror-symmetric in relation to two perpendicular axes spanning the collector edge contour;
the reflective surface of the collector is configured so that a bundle edge contour of the transformed radiation bundle in a downstream plane has a shape that is mirror-symmetric in relation to a maximum of one axis that is perpendicular to a main beam direction of the transformed radiation bundle in a vicinity of the plane;
the reflective surface of the collector is configured to convert the radiation into a family of images in the downstream plane;
the family of images includes a plurality of radiation source images; and
the bundle-guiding optical element is in the downstream plane.
17. A system having an illumination field, the system comprising:
a radiation source capable of emitting radiation;
a collector; and
a bundle-guiding optical element,
wherein:
the collector is a bundle-guiding optical collector configured to collect the radiation emitted by the radiation source and to form a transformed radiation bundle from a collected source-side radiation bundle;
the bundle-guiding optical collector comprises a reflective surface which is a first bundle-forming surface down-stream of the radiation source;
the reflective surface is configured to convert the radiation into a family of images in a downstream plane which is upstream of the illumination field of the system;
the family of images includes a plurality of radiation source images offset from each other in two dimensions relative to a beam direction of the trans-formed radiation bundle;
the family of images is arranged relative to each other in a non-rotationally symmetric manner with respect to the beam direction of the transformed radiation bundle so that the transformed radiation bundle in the downstream plane has a non-rotationally symmetric bundle edge contour relative to the beam direction of the transformed radiation bundle;
the bundle-guiding optical element is in the downstream plane; and
the system is an EUV illumination system.
18. The system according to claim 17 , wherein the non-rotationally symmetric bundle edge contour has at least a two-fold symmetry.
19. An apparatus, comprising:
an EUV illumination system, comprising:
a radiation source capable of emitting radiation;
a collector;
a bundle-guiding optical element; and
a projection objective configured to image an object field illuminated by the EUV illumination system into an image field in an image plane,
wherein:
the collector is a bundle-guiding optical collector configured to collect the radiation emitted by the radiation source and to form a trans-formed radiation bundle from a collected source-side radiation bundle;
the bundle-guiding optical collector comprises a reflective surface which is a first bundle-forming surface down-stream of the radiation source;
the reflective surface is configured to convert the radiation into a family of images in a downstream plane which is upstream of the object plane of the projection objective;
the family of images includes a plurality of radiation source images offset from each other in two dimensions relative to a beam direction of the trans-formed radiation bundle;
the family of images is arranged relative to each other in a non-rotationally symmetric manner with respect to the beam direction of the transformed radiation bundle so that the transformed radiation bundle in the downstream plane has a non-rotationally symmetric bundle edge contour relative to the beam direction of the transformed radiation bundle;
the bundle-guiding optical element is in the downstream plane; and
the apparatus is an EUV projection exposure apparatus.
20. The apparatus according to claim 19 , wherein the downstream plane does not coincide with a plane selected from the group consisting of a field plane of the projection objective, a pupil plane of the projection objective, a plane conjugated with the field plane of the projection objective, and a plane conjugated with the pupil plane of the projection objective.
21. The apparatus according to claim 19 , wherein the downstream plane coincides with a plane selected from the group consisting of a field plane of the projection objective, a pupil plane of the projection objective, a plane conjugated with the field plane of the projection objective, and a plane conjugated with the pupil plane of the projection objective.
22. The apparatus according to claim 19 , wherein the non-rotationally symmetric bundle edge contour has at least a two-fold symmetry.