Imaging euv optical unit for imaging an object field into an image field
OwnerAlexander WOLFinventor
Life of this patent
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Abstract
An imaging EUV optical unit serves images an object field into an image field. The imaging optical unit has a plurality of mirrors for guiding EUV imaging light along an imaging beam path. The plurality of the mirrors includes at least two normal incidence mirrors and at least one grazing incidence mirror. The last two mirrors in the imaging beam path are normal incidence mirrors and lack an imaging light passage opening. A reflection surface of an antepenultimate mirror in the imaging beam path faces the last mirror in the imaging beam path. This EUV optical unit can have improved usability for an EUV projection exposure apparatus.
Claims20
An imaging EUV optical unit configured to image an object field in an object plane into an image field in an image plane, the imaging EUV optical unit comprising:
- a plurality of mirrors configured to guide EUV imaging light along an imaging beam path from the object field towards the image field, wherein:
- the EUV imaging light has a wavelength of less than 30 nanometers;
- the plurality of mirrors comprises two normal incidence (NI) mirrors and two grazing incidence (GI) mirrors;
- the plurality of mirrors comprises a last mirror in the imaging beam path, a penultimate mirror in the imaging beam path and an antepenultimate mirror in the imaging beam path;
- the penultimate mirror is an NI mirror lacking a passage opening for the imaging light;
- the last mirror is an NI mirror lacking a passage opening for the imaging light;
- the antepenultimate mirror comprises a reflection surface facing the last mirror;
- and
- an overall transmission of the plurality of mirrors for the EUV imaging light is greater than 10%.
Dependencies are inferred from the claim text.