Catoptric objectives and systems using catoptric objectives
View Patent ↗In general, in one aspect, the invention features an objective arranged to image radiation from an object plane to an image plane, including a plurality of elements arranged to direct the radiation from the object plane to the image plane, wherein the objective has an image side numerical aperture of more than 0.55 and a maximum image side field dimension of more than 1 mm, and the objective is a catoptric objective.
1. An objective arranged to image radiation from an object plane to an image plane, the objective comprising:
a plurality of elements arranged to direct the radiation from the object plane to the image plane,
wherein:
the objective has an image side numerical aperture of about 0.4 or more,
the objective is a catoptric objective having a first element that has an opening for passage of the radiation from the object plane to the image plane,
the objective has a field independent obscuration related to the opening that is less than 30% of an aperture radius at a pupil plane of the objective,
a central portion of the pupil plane is obscured,
the objective defines an optical axis,
the optical axis intersects the central portion of the pupil plane, and
the objective is configured to be used in a microlithography projection exposure apparatus.
2. The objective of claim 1 , wherein the plurality of elements includes at least one element that does not have an opening.
3. The objective of claim 1 , wherein the objective has a maximum image side field dimension of more than 1 mm.
4. The objective of claim 1 , wherein the radiation has a wavelength λ of about 100 nm or less.
5. The objective of claim 1 , wherein for a meridional section of the objective, the radiation has a maximum angle of incidence on a surface of each of the elements of less than 22°.
6. The objective of claim 1 , wherein the plurality of elements includes no more than six elements.
7. The objective of claim 1 , wherein the plurality of elements includes more than six elements.
8. The objective of claim 7 , wherein the plurality of elements includes eight elements.
9. The objective of claim 1 , wherein the plurality of elements includes a second element that has an opening for passage of the radiation from the object plane to the image plane.
10. The objective of claim 1 , wherein the plurality of elements comprises a first group of elements and a second group of elements, the first group of elements being arranged to image the radiation from the object plane to a first intermediate-image plane, and the second group of elements being arranged to image the radiation from the intermediate-image plane to the image plane.
11. The objective of claim 10 , wherein none of the elements in the first group of elements includes an opening.
12. The objective of claim 10 , wherein at least one of the elements in the second group of elements includes an opening for passage of the radiation from the object plane to the image plane.
13. The objective of claim 1 , wherein at least one of the elements is rotationally symmetric with respect to the optical axis.
14. The objective of claim 1 , wherein at least one of the elements is not rotationally symmetric with respect to the optical axis.
15. A lithography tool, comprising the objective of claim 1 and an illumination system which during operation directs the radiation to the object plane.
16. The lithography tool of claim 15 , wherein the radiation from the illumination system is incident at the object plane at angles of about 10° or less.
17. An objective arranged to image radiation from an object plane to an image plane, the objective comprising:
a plurality of elements arranged to direct the radiation from the object plane to the image plane,
wherein:
the objective has an image side numerical aperture of about 0.4 or more,
the objective is a catoptric objective having a first element that has an opening for passage of the radiation from the object plane to the image plane,
the objective has a field independent obscuration related to the opening that is less than 30% of an aperture radius at a pupil plane of the objective,
the pupil plane has a central portion having a perimeter that defines an entire area of the central portion of the pupil plane,
the entire area of the central portion of the pupil plane is obscured, and
the objective is configured to be used in a microlithography projection exposure apparatus.