Projection system for EUV lithography
View Patent ↗There is provided an EUV optical projection system. The system includes a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, and a sixth mirror situated in an optical path from an object plane to an image plane, for imaging an object in said object plane into an image in said image plane. The image has a width W and a secant length SL, and the width W is greater than about 2 mm.
1. An EUV optical projection system, comprising:
a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, and a sixth mirror situated in an optical path from an object plane to an image plane, for imaging an object in said object plane into an image in said image plane,
wherein said image has a width W and a secant length SL,
wherein said width W is greater than about 2 mm,
wherein said system has a numerical aperture greater than 0.2 at said image, and forms an intermediate image along said optical path.
2. The system according to claim 1 , wherein said width W is between about 2 mm and about 3 mm.
3. The system according to claim 1 , wherein said intermediate image is formed between said second mirror and said third mirror.
4. The system according to claim 1 , said second mirror is concave.
5. The system according to claim 1 , wherein said third mirror is convex.
6. The system according to claim 1 , further comprising an aperture stop located along said optical path, between said first mirror and said second mirror.
7. The system according to claim 6 , wherein said aperture stop is not located on said first mirror, and not located on said second mirror.
8. The system according to claim 1 , wherein said first mirror is concave, said fourth mirror is concave, said fifth mirror is convex, and said sixth mirror is concave.
9. The system according to claim 1 , wherein said system has a RMS wavefront error of less than or equal to 0.017λ.
10. An EUV optical projection system, comprising:
a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror, and a sixth mirror situated in an optical path from an object plane to an image plane, for imaging an object in said object plane into an image in said image plane,
wherein said third mirror is convex,
wherein said image has a width W and a secant length SL,
wherein said width W is greater than about 2 mm, and
wherein said system has a RMS wavefront error of less than or equal to 0.017λ.
11. The system according to claim 10 , wherein said width W is between about 2 mm and about 3 mm.
12. The system according to claim 10 , wherein said system forms an intermediate image along said optical path.
13. The system according to claim 12 , wherein said intermediate image is formed between said second mirror and said third mirror.
14. The system according to claim 12 , wherein said second mirror is concave.
15. The system according to claim 10 , further comprising an aperture stop located along said optical path, between said first mirror and said second mirror.
16. The system according to claim 15 , wherein said aperture stop is not located on said first mirror, and not located on said second mirror.
17. The system according to claim 10 , wherein said first mirror is concave, said fourth mirror is concave, said fifth mirror is convex, and said sixth mirror is concave.