Catadioptric illumination system for metrology
AssigneeASML Holding N.V.
InventorsStanislav Y. Smirnov, Yevgeniy Konstantinovich Shmarev
Life of this patent
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Abstract
A catadioptric optical system operates in a wide spectral range. In an embodiment, the catadioptric optical system includes a first reflective surface positioned and configured to reflect radiation; a second reflective surface positioned and configured to reflect radiation reflected from the first reflective surface as a collimated beam, the second reflective surface having an aperture to allow transmission of radiation through the second reflective surface; and a channel structure extending from the aperture toward the first reflective surface and having an outlet, between the first reflective surface and the second reflective surface, to supply radiation to the first reflective surface.
Claims20
A metrology tool, comprising:
- an objective to deliver radiation to a surface and to receive radiation redirected by the surface;
- a detector to receive the redirected radiation from the objective;
- and
- an illumination system to deliver the radiation for redirection to the objective, the illumination system comprising an illumination system catadioptric optical system, the illumination system catadioptric optical system comprising:
- a first reflective surface positioned and configured to reflect radiation,
- a second reflective surface positioned and configured to reflect radiation reflected from the first reflective surface as a collimated beam, the second reflective surface having an aperture to allow transmission of radiation through the second reflective surface, and
- a channel structure extending from the aperture toward the first reflective surface and having an outlet, between the first reflective surface and the second reflective surface, to supply radiation to the first reflective surface.
A catadioptric optical system, comprising:
- a first reflective surface positioned and configured to reflect radiation;
- a second reflective surface positioned and configured to reflect radiation reflected from the first reflective surface as a collimated beam, the second reflective surface having an aperture to allow transmission of radiation through the second reflective surface;
- and
- a channel structure extending from the aperture toward the first reflective surface and having an outlet, between the first reflective surface and the second reflective surface, to supply radiation to the first reflective surface.
A metrology method, comprising:
- delivering radiation to a surface using an objective;
- receiving radiation redirected by the surface using the objective;
- detecting a parameter of the surface using the redirected radiation from the objective;
- and
- delivering the radiation for redirection to the objective using a catadioptric optical system, wherein delivering the radiation for redirection comprises:
- reflecting radiation using a first reflective surface of the catadioptric optical system, and
- reflecting radiation reflected from the first reflective surface using a second reflective surface to form a collimated beam, the second reflective surface having
- an aperture to allow transmission of radiation through the second reflective surface,
- wherein a channel structure extends from the aperture toward the first reflective surface and has an outlet, between the first reflective surface and the second reflective surface, to supply radiation to the first reflective surface.
Dependencies are inferred from the claim text.