| 摘要 |
An imaging optical unit (7) for a projection exposure apparatus serves for imaging an object field (4) in an object plane (5) into an image field (8) in an image plane (9). The image field (8) is arranged at a field distance (FA) from the object plane (5). The optical unit (7) has a plurality of mirrors (M1 to M8) which predefine beam path sections (171 to 179) of an imaging beam path (17). An object region (18) of the optical unit (7) is bounded by the object plane (5) and an object-side intermediate plane (19) parallel thereto. Said object-side intermediate plane is that plane at the smallest distance from the object plane (5) for which it holds true that the used reflection surfaces of all mirrors (M2, M4, M6) which are at a distance from the object plane (5) that is less than half of the field distance (FA) are arranged between the object plane (5) and the object-side intermediate plane (19). An image region (20) of the optical unit (7) is bounded by an image-side intermediate plane (21) parallel to the object plane (5) and an image field reference plane (22). The latter contains a central image field point and runs parallel to the object plane (5). The image-side intermediate plane (21) is that plane at the largest distance from the object plane (5) for which it holds true that, the used reflection surfaces of all mirrors (M1, M3, M5, M7 and M8) which are at a distance from the object plane (5) that is greater than half of the field distance (FA) are arranged beyond the image-side intermediate plane (21). An intermediate region (23) of the optical unit (7) is arranged between the intermediate planes (19, 21). A distance (A) between the intermediate planes (19, 21) is at least 40% of the field distance (FA). At least two beam path sections (171 to 177) pass completely through the intermediate region (23). The result is an imaging optical unit having small angles of incidence or small angle-of-incidence bandwidths. |
