System for measuring the image quality of an optical imaging system
AssigneeCarl Zeiss SMT GmbH
InventorsMarkus Mengel, Ulrich Wegmann, Albrecht Ehrmann, Wolfgang Emer, Reiner Clement, Ludo Mathijssen
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Abstract
Methods for measuring the image quality of a projection objective include providing a measuring structure on an image-side of the projection objective, providing an immersion fluid between the projection objective and the measuring structure, directing light through the projection objective and the immersion fluid to the measuring structure while shielding the measuring structure from the immersion fluid, detecting light transmitted by the measuring structure, and determining an image quality of the projection objective based on the detected light.
Claims22
A microlithography projection exposure system, comprising:
- an illumination system for providing radiation having a wavelength of 193 nm;
- a projection objective comprising a plurality of optical elements for imaging a pattern arranged in an object plane of the projection objective to an image plane of the projection objective using the radiation, the projection objective being configured for imaging when an immersion liquid is positioned between the image plane and an optical element of the plurality of optical elements located closest to the image plane;
- a measuring system for measuring at least one imaging parameter of the projection objective, the measuring system comprising:
- a substrate formed from a material transparent to the radiation;
- a layer of material opaque to the radiation;
- at least one aperture formed in the layer of opaque material;
- a detector positioned, during operation, to detect radiation transmitted by the at least one aperture;
- and
- an evaluation device in communication with the detector and programmed so that during operation the evaluation device determines a value for the at least one imaging parameter based on the detected radiation,
- wherein the microlithography projection exposure system is configured to position the measuring system relative to the projection objective so that the at least one aperture is located at the image plane and to provide the immersion liquid between the image plane and the optical element closest to the image plane during operation,
- wherein the measuring system further comprises a protective system positioned, during operation, between the layer of material and the optical element closest to the image plane.
Dependencies are inferred from the claim text.