Method of determining lens materials for a projection exposure apparatus

US7239450B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Vladimir Kamenov · Oberkochen, DE
• Daniel Kraehmer · Aalen, DE
• Michael Totzeck · Schwäbisch Gmünd, DE
• Toralf Gruner · Hennef (Sieg), DE
• Aurelian Dodoc · Heidenheim an der Brenz, DE

Key dates

• Filing date: Jul 14, 2005
• Grant date: Jul 3, 2007
• Expiry date: Jul 14, 2025

Classification

• Technology area (CPC G): Physics
• CPC primary: G03F7/70966
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A method of determining materials of lenses contained in an optical system of a projection exposure apparatus is described. First, for each lens of a plurality of the lenses, a susceptibility factor KLT/LH is determined. This factor is a measure of the susceptibility of the respective lens to deteriorations caused by at least one of lifetime effects and lens heating effects. Then a birefringent fluoride crystal is selected as a material for each lens for which the susceptibility factor KLT/LH is above a predetermined threshold. Theses lenses are assigned to a first set of lenses. For these lenses, measures are determined for reducing adverse effects caused by birefringence inherent to the fluoride crystals.