Imaging optical unit for a metrology system for examining a lithography mask
First Claim
1. An imaging optical unit for a metrology system for examining a lithography mask, wherein the lithography mask can be arranged in an object field of the imaging optical unit, the object field being defined by two mutually perpendicular object field coordinates, the imaging optical unit comprising:
- an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1, in which the aperture stop is arranged on a mirror of the imaging optical unit, and the mirror is configured to reflect imaging light within an edge contour of the aperture stop; and
at least four mirrors, which are arranged in an imaging-light path between the object field and an image field,wherein the imaging optical unit comprises an isomorphic configuration in which an imaging scale in the direction of one of the two object field coordinates does not differ from an imaging scale in the direction of the other of the two object field coordinates.
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Abstract
An imaging optical unit serves within a metrology system for examining a lithography mask. The lithography mask can be arranged in an object field of the imaging optical unit. The object field is defined by two mutually perpendicular object field coordinates. The imaging optical unit has an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1. This results in an imaging optical unit which can be used for the examination of lithography masks that are designed for projection exposure with an anamorphic projection optical unit.
18 Citations
21 Claims
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1. An imaging optical unit for a metrology system for examining a lithography mask, wherein the lithography mask can be arranged in an object field of the imaging optical unit, the object field being defined by two mutually perpendicular object field coordinates, the imaging optical unit comprising:
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an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1, in which the aperture stop is arranged on a mirror of the imaging optical unit, and the mirror is configured to reflect imaging light within an edge contour of the aperture stop; and at least four mirrors, which are arranged in an imaging-light path between the object field and an image field, wherein the imaging optical unit comprises an isomorphic configuration in which an imaging scale in the direction of one of the two object field coordinates does not differ from an imaging scale in the direction of the other of the two object field coordinates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An imaging optical unit for a metrology system for examining a lithography mask
wherein the lithography mask can be arranged in an object field of the imaging optical unit, the object field being defined by two mutually perpendicular object field coordinates, comprising an anamorphic configuration in which an imaging scale in the direction of one of the two object field coordinates differs from an imaging scale in the direction of the other of the two object field coordinates.
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14. A metrology system for examining a lithography mask, comprising:
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an illumination optical unit for illuminating the lithography mask to be examined, an imaging optical unit in which the lithography mask can be arranged in an object field of the imaging optical unit, the object field being defined by two mutually perpendicular object field coordinates, the imaging optical unit comprising; an aperture stop of which the aspect ratio in the direction of the two object field coordinates differs from 1; and at least four mirrors, which are arranged in an imaging-light path between the object field and an image field, and a spatially resolving detection device, arranged in an image field of the imaging optical unit. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification