Schott Ag

Hellma Materials Gmbh & Co. Kg

Hellma Materials Gmbh

Regina Martin

Lutz Parthier

Wolfgang Triebel

Christian Muehlig

Jochen Alkemper

Gordon Von Der Goenna

Gabriela Toepfer

Karin Poehl

Martin Letz

Gunther Wehrhan

Joerg Staeblein

Klaus Petermann

Konrad Knapp

Christian MÜHLIG

A method is described for quantitative determination of suitability of an optical material, especially alkali halide and alkaline earth halide single crystals, for optical components exposed to high energy densities, especially of pulsed laser light at wavelengths under 250 nm. In this procedure radiation-dependent transmission of the optical material is determined at ultraviolet wavelengths by fluorescence measurements for fluorescence induced by ultraviolet radiation at these ultraviolet wavelengths. This is accomplished by a method including determining an induced fluorescence maximum of a non-linear absorption process, measuring a slope (|dT/dH|) of a functional relationship representing the dependence of the radiation-dependent transmission on fluence (H) for the induced fluorescence and determining radiation-dependent transmissions from this slope for particular fluence values.

Method for quantitative determination of the suitability of crystals for optical components exposed to high energy densities, crystals graded in this way and uses thereof

An optical material for lithographic applications is selected from crystal materials by a testing method. The crystal materials are preferably quartz and/or alkali or alkaline earth halides, especially fluorides, or mixed crystals. The testing method includes three tests to measure irreversible radiation damage: 1) the optical material is irradiated with ultraviolet radiation at 193 nm and the non-intrinsic fluorescence intensity at 740 nm is measured; 2) the optical material is irradiated with high energy density laser light and a change in respective absorptions before and after irradiation at 385 nm is measured; and 3) the optical material is irradiated with an X-ray or radioactive source to form all possible color centers and a difference of respective surface integrals of corresponding absorption spectra in ultraviolet spectral and/or visible spectral regions is measured before and after irradiation.

Method of testing optical materials by irradiating with high energy density radiation, optical materials selected by said method and uses thereof

The optical elements for ultraviolet radiation, especially for microlithography, are made from cubic granet, cubic spinel, cubic perovskite and/or cubic M(II)- as well as M(IV)-oxides. The optical elements are made from suitable crystals of YAlO, LuAlO, CaAlSiO, KNaAlF, KNaScF, KLiAlFand/or NaAlLiF, (Mg, Zn)AlO, CaAlO, CaBOand/or LiAlO, BaZrOand/or CaCeO. A front lens used in immersion optics for microlithography at wavelengths under 200 nm is an example of a preferred optical element of the present invention.

Method for making optical elements for microlithography, the lens systems obtained by the method and their uses

The method determines the extent of irreversible radiation damage of an optical material. The method includes the following three tests to determine the extent of irreversible radiation damage: 1) the optical material is irradiated with ultraviolet radiation at a wavelength of 193 nm and the non-intrinsic fluorescence intensity at a wavelength of 740 nm is measured; 2) the optical material is irradiated with high energy laser light and a change in respective absorptions at a wavelength of 385 nm is determined before and after irradiation; and 3) the optical material is irradiated with an energetic radiation source to form all possible color centers and a difference of respective surface integrals of corresponding absorption spectra in ultraviolet spectral and/or visible spectral regions is measured before and after irradiation.

Method for determination of irreversible radiation damage of optical materials

The method tests the suitability of an optical material having a radiation-induced absorption, especially of an alkali or alkaline earth halide, for production of an optical element exposed to high-energy irradiation. The method includes pre-irradiating the optical material with laser radiation until rapid damage induced in the optical material with the laser radiation is saturated; subsequently measuring fluorescence of the optical material during and/or immediately after irradiating the optical material with excitation radiation and determining the non-intrinsic fluorescence and intrinsic fluorescence present in the measured fluorescence. Suitability may be preferably determined according to a ratio of the amount of non-intrinsic fluorescence to intrinsic fluorescence. A device for performing the method including a barrier device for blocking scattered excitation radiation is also provided.

Determining the suitability of an optical material for the production of optical elements, corresponding device, and use of said material

A method is described for quantitative determination of suitability of an optical material, especially alkali halide and alkaline earth halide single crystals, for optical components exposed to high energy densities, especially of pulsed laser light at wavelengths under 250 nm. In this procedure radiation-dependent transmission of the optical material is determined at ultraviolet wavelengths by fluorescence measurements for fluorescence induced by ultraviolet radiation at these ultraviolet wavelengths. This is accomplished by a method including determining an induced fluorescence maximum of a non-linear absorption process, measuring a slope (|dT/dH|) of a functional relationship representing the dependence of the radiation-dependent transmission on fluence (H) for the induced, fluorescence and determining radiation-dependent transmissions from this slope for particular fluence values.

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Jena, Germany

Regina Martin