| 摘要 |
An all-refelctive optical system for a projection photolithography camera has a source of EUV radiation, a wafer and a mask to be imaged on the wafer. The optical system includes a first concave mirror, a second mirror, a third convex mirror, a fourth concave mirror, a fifth convex mirror and a sixth concave mirror. The system is configured such that five of the six mirrors receives a chief ray at an incidence angle less than substantially 12 DEG , and each of the six mirrors receives a chief ray at an incidence angle of less than substantially 15 DEG . Four of the six reflecting surfaces have an aspheric departure of less than substantially 7 mu m. Five of the six reflecting surfaces have an aspheric departure of less than substantially 14 mu m. Each of the six refelecting surfaces has an aspheric departure of less than 16.0 mu m.
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