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

US7209292B2 · 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: May 30, 2003
• Grant date: Apr 24, 2007
• Expiry date: Mar 23, 2024

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. The projection objective includes optical elements arranged along an optical axis thereof, which include a first group of elements following the object plane and a last optical element following the first group, which is arranged near the image plane. The last optical element defines 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 or only slight curvature. The method includes 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 axially displacing the last optical element to set a working distance.