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

US9606446B2 · kind B2 · utility

Assignee

• Carl Zeiss SMT GmbH · DE

Inventors

• Norbert Wabra · Werneck, DE
• Boris Bittner · Roth, DE
• Martin von Hodenberg · Oberkochen, DE
• Hartmut Enkisch · Aalen, DE
• Stephan Muellender · Aalen, DE
• Olaf Conradi · Sonthofen, DE

Key dates

• Filing date: Jun 5, 2015
• Grant date: Mar 28, 2017
• Expiry date: Sep 16, 2035

Classification

• Technology area (CPC G): Physics
• CPC primary: G21K1/062
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

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.