Carl-zeiss-smt Ag

Daniel Krähmer

Michael Gerhard

Wilhelm Ulrich

Toralf Gruner

Manfred Maul

Christian Wagner

Winfried M Kaiser

Birgit Enkisch

Martin Brunotte

Christof Zaczek

Eric Eva

An objective for a microlithography projection system has at least one fluoride crystal lens. The effects of birefringence, which are detrimental to the image quality, are reduced if the lens axis of the crystal lens is oriented substantially perpendicular to the {100}-planes or {100}-equivalent crystallographic planes of the fluoride crystal. If two or more fluoride crystal lenses are used, they should have lens axes oriented in the (100)-, (111)-, or (110)-direction of the crystallographic structure, and they should be oriented at rotated positions relative to each other. The birefringence-related effects are further reduced by using groups of mutually rotated (100)-lenses in combination with groups of mutually rotated (111)- or (110)-lenses. A further improvement is also achieved by applying a compensation coating to at least one optical element of the objective.

Objective with fluoride crystal lenses

Radiation-induced damage to a lens material in a projection exposure system is reduced by selection of maximum design fluence values Hfor lenses and at least one lens made of a material having a characteristic transition point Tafter exposure to a given amount of radiation, wherein, for instance, T&#x3c;0.8. Hamong other relationships and/or characteristics of the lenses.

Projection optical system

An objective (), in particular for a microlithography projection apparatus, has lenses or lens parts falling into at least two groups. The first group () is made of a first crystalline material and the second group () is made of a second crystalline material. In the first group (), an outermost aperture ray () is subject to a first optical path difference between two mutually orthogonal states of linear polarization; and the same outermost aperture ray is subject to a second optical path difference in the second group (). The two different crystalline materials are selected so that the first and second optical path difference approximately compensate each other. A suitable selection consists of calcium fluoride for the first and barium fluoride for the second crystalline material.

Objective with lenses made of a crystalline material

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Aalen, Germany

Daniel Krähmer