PROJECTION SYSTEM FOR EUV LITHOGRAPHY

摘要

An EUV optical projection system includes at least six reflecting surfaces for imaging an object (OB) on an image (IM). The system is preferably configured to form an intermediate image (IMI) along an optical path from the object (OB) to the image (IM) between a secondary mirror (M2) and a tertiary mirror (M3), such that a primary mirror (M1) and the secondary mirror (M2) form a first optical group (G1) and the tertiary mirror (M3), a fourth mirror (M4), a fifth mirror (M5) and a sixth mirror (M6) form a second optical group (G2). The system also preferably includes an aperture stop (APE) located along the optical path from the object (OB) to the image (IM) between the primary mirror (M1) and the secondary mirror (M2). The secondary mirror (M2) is concave, and the tertiary mirror (M3) is convex. Each of the six reflecting surfaces preferably receives a chief ray (CR) from a central field point at an incidence angle of less than substantially 15 DEG .