Imaging optical system and projection exposure system including the same
AssigneeCarl Zeiss SMT GmbH
InventorsHans-Juergen Mann, Wilheim Ulrich, Stephan Muellender, Hartmut Enkisch
Life of this patent
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Abstract
An imaging optical system has a plurality of mirrors. These image an object field in an object plane into an image field in an image plane. In the imaging optical system, the ratio of a maximum angle of incidence of imaging light) on reflection surfaces of the mirrors and an image-side numerical aperture of the imaging optical system is less than 33.8°. This can result in an imaging optical system which offers good conditions for a reflective coating of the mirror, with which a low reflection loss can be achieved for imaging light when passing through the imaging optical system, in particular even at wavelengths in the EUV range of less than 10 nm.
Claims29
An imaging optical system which during operation directs light along a path from an object plane to an image plane to image an object field in the object plane into an image field in the image plane, the imaging optical system comprising:
- a plurality of mirrors arranged to direct the light along the path,
- wherein:
- for each mirror of the plurality of mirrors, during operation of the imaging optical system, the light is incident on the mirror at an angle of incidence;
- for each mirror of the plurality of mirrors, the mirror has a reflectivity at the angle of incidence for light having a wavelength which is less than 10 nm;
- the plurality of mirrors has an average reflectivity based on the reflectivity for each mirror at the angle of incidence for that mirror for the light having the wavelength which is less than 10 nm;
- and
- the average reflectivity of the plurality of mirrors is greater than 50% for the light having the wavelength which is less than 10 nm.
An imaging optical system which during operation directs light along a path from an object plane to an image plane to image an object field in the object plane into an image field in the image plane, the imaging optical system comprising:
- a plurality of mirrors arranged to direct the light along the path,
- wherein at least one of the plurality of mirrors comprises a coating which comprises a plurality of B4C/CsI bilayers.
An imaging optical system which during operation directs light along a path from an object plane to an image plane to image an object field in the object plane into an image field in the image plane, the imaging optical system comprising:
- a plurality of mirrors arranged to direct the light along the path,
- wherein:
- for each mirror of the plurality of mirrors, during operation of the imaging optical system, the light is incident on the mirror at an angle of incidence;
- for each mirror of the plurality of mirrors, the mirror has a reflectivity at the angle of incidence for light having a wavelength which is less than 6.9 nm;
- the plurality of mirrors has an average reflectivity based on the reflectivity for each mirror at the angle of incidence for that mirror for the light having the wavelength which is less than 6.9 nm;
- and
- the average reflectivity of the plurality of mirrors is greater than 58% for the light having the wavelength which is less 6.9 nm.
An imaging optical system which during operation directs light along a path from an object plane to an image plane to image an object field in the object plane into an image field in the image plane, the imaging optical system comprising:
- a plurality of mirrors arranged to direct the light along the path,
- wherein:
- each of the mirrors comprises a reflective coating for light having a wavelength which is less than 10 nm;
- the plurality of mirrors has an average reflectivity which is greater than 50% for the light having the wavelength which is less 10 nm;
- and
- at least one of the plurality of mirrors comprises a coating which comprises a plurality of B4C/CsI bilayers.
Dependencies are inferred from the claim text.