Patent Number: 7,355,678

Title: Projection system for EUV lithography

Abstract: 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 preferably concave, and the tertiary mirror (M3) is preferably 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.degree.. The system preferably has a numerical aperture greater than 0.18 at the image (IM). The system is preferably configured such that a chief ray (CR) converges toward the optical axis (OA) while propagating between the secondary mirror (M2) and the tertiary mirror (M3).

Inventors: Hudyma; Russell (San Ramon, CA), Mann; Hans-Jurgen (Oberkochen, DE), Dinger; Udo (Oberkochen, DE)

Assignee: Carl Zeiss SMT AG

International Classification: G03B 27/54 (20060101); G03B 27/42 (20060101)

Expiration Date: 2020-04-08 0:00:00