Optical assembly with suppression of degradation

US9632436B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Stefan Schmidt · Aalen, DE
• Dirk Heinrich Ehm · Beckingen, DE
• Markus Walter · Wertheim, DE

Key dates

• Filing date: Jan 22, 2014
• Grant date: Apr 25, 2017
• Expiry date: Dec 26, 2034

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F7/70983
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An optical assembly including: a beam generating system generating radiation (6) at an operating wavelength, an optical element (13, 14) arranged in a residual gas atmosphere (16) and subjected to the radiation, which induces a degradation of a surface of the optical element, and a feed device feeding at least one gaseous constituent into the residual gas atmosphere, to suppress the degradation of the surface. Either a beam diameter (d) of the radiation at the surface of the optical element, lies above a threshold value (dc), thereby suppressing the degradation by the gaseous constituent, or, if the beam diameter (d) at the surface (14a) of the optical element (14) lies below the threshold value (dc) so that the effectiveness of the suppression of the degradation is reduced, at least one further device (25, 27) enhancing suppression of the degradation of the surface (14a) is assigned to the optical element (14).