Mirror, projection objective with such mirror, and projection exposure apparatus for microlithography with such projection objective

US9575224B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Rolf Freimann · Aalen, DE
• Norman Baer · Aalen, DE
• Guido Limbach · Aalen, DE
• Thure Boehm · Aalen, DE
• Gero Wittich · Aalen, DE

Key dates

• Filing date: Mar 18, 2013
• Grant date: Feb 21, 2017
• Expiry date: Jul 6, 2034

Classification

• Technology area (CPC G): Physics
• CPC primary: G21K2201/061
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A mirror (1a; 1a′; 1b; 1b; 1c; 1c′) with a substrate (S) and a layer arrangement configured such that light (32) having a wavelength below 250 nm and incident on the mirror at at least an angle of incidence of between 0° and 30° is reflected with more than 20% of its intensity. The layer arrangement has at least one surface layer system (P′″) having a periodic sequence of at least two periods (P3) of individual layers, wherein the periods (P3) include a high refractive index layer (H′″) and a low refractive index layer (L′″). The layer arrangement has at least one graphene layer. Use of graphene (G, SPL, B) on optical elements reduces surface roughness to below 0.1 nm rms HSFR and/or protects the EUV element against a radiation-induced volume change of more than 1%. Graphene is also employed as a barrier layer to prevent layer interdiffusion.