Reflective optical element for EUV lithography and method of manufacturing a reflective optical element

• Main Authors: Muellender Stephan, Wabra Norbert, Bittner Boris, Von Hodenberg Martin, Conradi Olaf, Enkisch Hartmut
• Format: Patent
• Language: English
• Published: 28.03.2017
• Subjects: APPARATUS SPECIALLY ADAPTED THEREFOR; CINEMATOGRAPHY; ELECTROGRAPHY; GAMMA RAY OR X-RAY MICROSCOPES; HOLOGRAPHY; IRRADIATION DEVICES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES; MATERIALS THEREFOR; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; NANOTECHNOLOGY; NUCLEAR ENGINEERING; NUCLEAR PHYSICS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; ORIGINALS THEREFOR; PERFORMING OPERATIONS; PHOTOGRAPHY; PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES,e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTORDEVICES; PHYSICS; SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOTOTHERWISE PROVIDED FOR; TRANSPORTING

A reflective optical element of an optical system for EUV lithography and an associated manufacturing method. The reflective optical element (20) includes a multilayer system (23, 83) for reflecting an incident electromagnetic wave having an operating wavelength in the EUV range, the reflected wave having a phase φ, and a capping layer (25, 85) made from a capping layer material. The method includes determining a dependency according to which the phase of the reflected wave varies with the thickness d of the capping layer, determining a linearity-region in the dependency in which the phase of the reflected wave varies substantially linearly with the thickness of the capping layer, and creating a thickness profile in the capping layer such that both the maximum thickness and the minimum thickness in the thickness profile are in the linearity-region.