Removing reflective layers from EUV mirrors

US7919004B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Martin Weiser · Sinsheim, DE
• Olaf Bork · Aalen, DE
• Ulrich Andiel · Ulm, DE

Key dates

• Filing date: Aug 3, 2009
• Grant date: Apr 5, 2011
• Expiry date: Oct 29, 2029

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F1/72
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A method for removing at least one reflective layer (4a, 4b) from an optical element (1) for EUV lithography, wherein the optical element (1) has a substrate (2) and an interlayer (6) between the substrate (2) and the at least one reflective layer (4a, 4b). The method includes etching away the at least one reflective layer (4a, 4b) as far as the interlayer (6) with an etching gas (7), wherein the material of the interlayer (6) does not react with the etching gas (7), and wherein, after the etching away, the interlayer (6) has a surface roughness of less than 0.5 nm rms, preferably of less than 0.2 nm rms, and more preferably of less than 0.1 nm rms. Also, an optical element (1) for reflecting radiation in the EUV wavelength range includes a substrate (2), at least one reflective layer (4a, 4b), and an interlayer (6) arranged between the substrate (2) and the at least one reflective layer (4a, 4b). The interlayer (6) is composed at least partly of a material which does not react with a halogen or a halogen compound as etching gas (7) and which is selected, in particular, from one or more of the following: alkali metal halides, alkaline earth metal halides and aluminum oxide (Al2O3).…