Projection Lens for a Microlithographic Projection Exposure Apparatus

Abstract

A projection lens for a EUV microlithographic projection exposure apparatus comprises a diaphragm (BL) which is arranged at a distance (D) in front of a mirror (S 2 ) of the lens. The diaphragm (BL) has a non-round aperture with an edge contour that may be configured such two rays of a light bundle disposed symmetrically with respect to a chief ray are treated equally, i.e. either both rays pass through the diaphragm aperture or both are blocked by the diaphragm.

1 . A projection lens for a microlithographic exposure apparatus, comprising: 
 a. a mirror on which a chief ray of a light bundle falls obliquely with respect to a mirror axis,    b. a diaphragm arranged at a distance in front of the mirror, said diaphragm having a diaphragm aperture with a non-round edge contour for controlling a light flux impinging on and reflected from the mirror.