Projection objective having mirror elements with reflective coatings

US8279404B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Danny Chan · Fremont, US
• Hans-Juergen Mann · Oberkochen, DE
• Sascha Migura · Aalen, DE

Key dates

• Filing date: Feb 10, 2010
• Grant date: Oct 2, 2012
• Expiry date: Feb 18, 2031

Classification

• Technology area (CPC G): Physics
• CPC primary: G21K2201/067
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

An optical system is disclosed that includes a plurality of elements arranged to image radiation at a wavelength λ from an object field in an object surface to an image field in an image surface. The elements include mirror elements having a reflective surface formed by a reflective coating positioned at a path of radiation. At least one of the mirror elements has a rotationally asymmetrical reflective surface deviating from a best-fit rotationally symmetric reflective surface by about λ or more at one or more locations. The elements include an apodization correction element effective to correct a spatial intensity distribution in an exit pupil of the optical system relative to the optical system without the apodization correcting element. The apodization correction element can be effective to increase symmetry of the spatial intensity distribution in the exit pupil relative to the optical system without the apodization correcting element.