Catadioptric projection objective
View Patent ↗A catadioptric projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective has a first, refractive objective part for imaging the pattern provided in the object plane into a first intermediate image; a second objective part including at least one concave mirror for imaging the first intermediate imaging into a second intermediate image; and a third, refractive objective part for imaging the second intermediate imaging onto the image plane; wherein the projection objective has a maximum lens diameter D max , a maximum image field height Y′, and an image side numerical aperture NA; wherein COMP1=D max /(Y′·NA 2 ) and wherein the condition COMP1<10 holds.
1. A catadioptric projection objective for imaging a pattern provided in an object plane of the projection objective onto an image plane of the projection objective comprising:
a first, refractive objective part for imaging the pattern provided in the object plane into a first intermediate image;
a second objective part including at least one concave mirror for imaging the first intermediate image into a second intermediate image;
a third, refractive objective part for imaging the second intermediate image onto the image plane;
wherein: the projection objective has a maximum lens diameter D max , a maximum image field height Y′, and an image side numerical aperture NA;
wherein
COMP 1 =D max /( Y ′·NA 2 )
and wherein the following condition holds:
COMP 1<10.
2. Projection objective according to claim 1 , wherein NA>1.2.
3. Projection objective according to claim 1 , wherein a first concave mirror having a first continuous mirror surface and at least one second concave mirror having a second continuous mirror surface are arranged in the second objective part; pupil surfaces are formed between the object plane and the first intermediate image, between the first and the second intermediate images and between the second intermediate image and the image plane; and all concave mirrors are arranged optically remote from a pupil surface.
4. Projection objective according to claim 1 , having a number N L of lenses and a number N OP of imaging objective parts concatenated at intermediate images;
where
COMP 2= D max N L /( Y ′·NA 2 )
COMP 3 =D max N L /( N OP ·Y ′·NA 2 );
and wherein at least one of the following conditions holds:
COMP 2<300
COMP 3<100.
5. Projection objective according to claim 1 , wherein the projection objective includes at least one double asphere comprising a first aspheric surface and a second aspheric surface immediately adjacent to the first aspheric surface.
6. Projection objective according to claim 5 , wherein the double asphere is formed by facing adjacent aspheric surfaces of two subsequent lenses.
7. Projection objective according to claim 6 , wherein a distance, measured along the optical axis, between the first and second aspheric surfaces of the double asphere is smaller than a thickness, measured along the optical axis, of the thinner of two lenses forming the double asphere.
8. Projection objective according to claim 6 , wherein the third objective part includes at least one double asphere.
9. Projection objective according to claim 8 , wherein the double asphere is positioned optically between the second intermediate image and the pupil surface of the third objective part.
10. Projection objective according to claim 6 , wherein the first objective part includes at least one double asphere.
11. Projection objective according to claim 10 , wherein the double asphere is positioned optically close to or at a pupil surface of the first objective part.
12. Projection objective according to claim 1 , wherein the first objective part and the third objective part each include at least one double asphere formed by facing adjacent aspheric surfaces of two subsequent lenses.
13. Projection objective according to claim 1 , wherein the first objective part includes at least one lens having a lens surface where angles of incidence of rays transiting that lens surface include angles of incidence larger than 60°.
14. Projection objective according to claim 13 , wherein that lens surface is positioned optically close to the pupil surface.
15. Projection objective according to claim 1 , wherein an axial mirror-lens distance between a first lens of the third objective part and a vertex of a mirror geometrically nearest to that lens is more than 5% of an axial distance between the object surface OS and the image surface IS.
16. Projection objective according to claim 1 , wherein all concave mirrors have an aspheric mirror surface.
17. Projection objective according to claim 1 , wherein the first objective part, the second objective part and the third objective part share a common straight optical axis.
18. Projection objective according to claim 1 , wherein an aperture stop is positioned in the third objective part between a region of maximum beam diameter and the image surface in a region of a converging beam.
19. A projection-exposure system for use in microlithography having an illumination system and a catadioptric projection objective, wherein the projection objective is configured according to claim 1 .
20. A method for fabricating semiconductor devices or other types of micro devices, comprising:
providing a mask having a prescribed pattern;
illuminating the mask with ultraviolet light having a prescribed wavelength; and
projecting an image of the pattern onto a photosensitive substrate arranged in the vicinity of the image plane of a projection objective using a catadioptric projection objective according to of claim 1 .