Reflective Optical Element for EUV Lithography and Method of Manufacturing a Reflective Optical Element

摘要

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.

主权项

1. A method of manufacturing a reflective optical element of an optical system for extreme ultraviolet (EUV) lithography, wherein the reflective optical element comprises a multilayer system configured to reflect an incident electromagnetic wave having an operating wavelength in the EUV range, the reflected wave having a phase φ, and a capping layer made from a capping layer material and having a thickness d, wherein the method comprises:
determining, for the capping layer material, a dependency according to which the phase φ 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 a maximum value of the thickness and a minimum value of the thickness in the thickness profile are in the linearity-region.