High numerical aperture ring field projection system for extreme ultraviolet lithography

摘要

An all-reflective 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 of less than substantially 12°, and each of the six mirrors receives a chief ray at an incidence angle of less than substantially 15°. Four of the six reflecting surfaces have an aspheric departure of less than substantially 7 &mgr;m. Five of the six reflecting surfaces have an aspheric departure of less than substantially 14 &mgr;m. Each of the six reflecting surfaces has an aspheric departure of less than 16.0 &mgr;m.