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1. (WO2018010960) PROJECTION OPTICAL UNIT FOR EUV PROJECTION LITHOGRAPHY

Pub. No.:    WO/2018/010960    International Application No.:    PCT/EP2017/065936
Publication Date: Fri Jan 19 00:59:59 CET 2018 International Filing Date: Thu Jun 29 01:59:59 CEST 2017
IPC: G03F 7/20
G02B 17/06
Applicants: CARL ZEISS SMT GMBH
Inventors: SCHWAB, Markus
ENKISCH, Hartmut
SCHICKETANZ, Thomas
Title: PROJECTION OPTICAL UNIT FOR EUV PROJECTION LITHOGRAPHY
Abstract:
A projection optical unit (7) for EUV projection lithography has a plurality of mirrors (M1 to M10) for imaging an object field (4) into an image field (8) with illumination light (3). At least one of the mirrors (M1, M9, M10) is embodied as an NI mirror and at least one of the mirrors (M2 to M8) is embodied as a GI mirror. A mirror dimension Dx of the at least one NI mirror in a plane of extent (xz) perpendicular to a plane of incidence (yz) satisfies the following relationship: 4 LLWx/IWPVmax < Dx. A mirror dimension Dy of the at least one GI mirror in the plane of incidence (yz) satisfies the following relationship: 4 LLWy/(IWPVmax cos(a)) < Dy. Here, LLWx and LLWy denote the étendue of the projection optical unit (7) in the plane of extent (xz) and in the plane of incidence (yz) and IWPVmax denotes the maximum difference between a maximum angle of incidence and a minimum angle of incidence of the illumination light (3) on the reflection surface of the NI mirror (M1, M9, M10) and on the reflection surface of the GI mirror (M2 to M8). a denotes the angle of incidence of a chief ray (16) of the central field point on the reflection surface of the GI mirror (M2 to M8). This results in a projection optical unit which is optimizable, in particular for very short EUV illumination light wavelengths.