Projection objective, especially for microlithography, and method for adjusting a projection objective

US7310187B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Alexander Epple · Aalen, DE
• Paul Graeupner · Aalen, DE
• Winfried Kaiser · Cologne, DE
• Reiner Garreis · Aalen, DE
• Wilhelm Ulrich · Aalen, DE

Key dates

• Filing date: Apr 13, 2007
• Grant date: Dec 18, 2007
• Expiry date: Apr 13, 2027

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F7/70341
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A method of adjusting a projection objective permits the projection objective to be adjusted between an immersion configuration and a dry configuration with few interventions in the system, and therefore to be used optionally as an immersion objective or as a dry objective. The projection objective has a multiplicity of optical elements which are arranged along an optical axis of the projection objective, the optical elements comprising a first group of optical elements following the object plane and a last optical element following the first group, arranged next to the image plane and defining an exit surface of the projection objective which is arranged at a working distance from the image plane. The last optical element is substantially without refracting power and has no curvature or only slight curvature. The method comprises varying the thickness of the last optical element, changing the refractive index of the space between the exit surface and the image plane by introducing or removing an immersion medium, and preferably axial displacement of the last optical element in order to set a suitable working distance.