Objective for EUV microscopy, EUV lithography, and x-ray imaging
Disclosed is an imaging apparatus for EUV spectroscopy, EUV microscopy, EUV lithography, and x-ray imaging. This new imaging apparatus could, in particular, make significant contributions to EUV lithography at wavelengths in the range from 10 to 15 nm, which is presently being developed for the manufacturing of the next-generation integrated circuits. The disclosure provides a novel adjustable imaging apparatus that allows for the production of stigmatic images in x-ray imaging, EUV imaging, and EUVL. The imaging apparatus of the present invention incorporates additional properties compared to previously described objectives. The use of a pair of spherical reflectors containing a concave and convex arrangement has been applied to a EUV imaging system to allow for the image and optics to all be placed on the same side of a vacuum chamber. Additionally, the two spherical reflector segments previously described have been replaced by two full spheres or, more precisely, two spherical annuli, so that the total photon throughput is largely increased. Finally, the range of permissible Bragg angles and possible magnifications of the objective has been largely increased.
1. An adjustable apparatus for forming an image of an object, the apparatus comprising:
a. at least one pair of concentric spherical reflectors wherein the reflectors share a common center and wherein each pair includes a convex reflector containing a radius of curvature R 1 and a Bragg angle θ 1 , and a concave reflector containing a radius of curvature R 2 and a Bragg angle θ 2 ; wherein the spherical reflectors are concentric with a mathematical sphere that contains a radius RT, wherein:
RT=R 1 cos(θ 1 )= R 2 cos(θ 2 );
b. a ray pattern established by reflection of radiation from the object on the reflectors; and
c. an axis of symmetry of the ray pattern from the object, through the common center, to an image of the object and wherein the apparatus is configured to allow the ray pattern to be rotated about the axis.
2. An adjustable apparatus for forming an image of an object comprising:
a. at least one pair of concentric spherical reflectors wherein the reflectors share a common center and wherein each pair includes a convex reflector containing a radius of curvature R 1 and a Bragg angle θ 1 , and a concave reflector containing a radius of curvature R 2 and a Bragg angle θ 2 ; wherein the spherical reflectors are concentric with a mathematical sphere that contains a radius RT, wherein:
RT=R 1 cos(θ 1 )= R 2 cos(θ 2 );
b. a ray pattern established by reflection of radiation from the object on the reflectors; and
c. an axis of symmetry of the ray pattern from the object, through the common center, to an image of the object and wherein the apparatus is configured to allow the ray pattern to be rotated about the axis preserving the same Bragg angles after the rotation.
3. The apparatus of claim 1 wherein the spherical reflectors are spherical annuli.
4. The apparatus of claim 1 wherein the spherical reflectors are multi-layer structures configured to reflect EUV rays.
5. The apparatus of claim 4 wherein the multi-layer structures have uniform 2d spacings, 2d 1 and 2d 2 , across the two reflector surfaces, where d 1 and d 2 are the periods of the two multilayer structures.
6. The apparatus of claim 1 wherein the spherical reflectors are spherically bent crystals.
7. The apparatus of claim 1 wherein the spherical reflectors are spherically bent mirrors.
8. The apparatus of claim 7 further comprising an aperture to select the rays that reach the image of the object.
9. The apparatus of claim 1 wherein the object is a mask.
10. The apparatus of claim 2 wherein the spherical reflectors are spherical annuli.
11. The apparatus of claim 2 wherein the spherical reflectors are multi-layer structures configured to reflect EUV rays.
12. The apparatus of claim 11 wherein the multi-layer structures have uniform 2d spacings, 2d 1 and 2d 2 , across the two reflector surfaces, where d 1 and d 2 are the periods of the two multilayer structures.
13. The apparatus of claim 2 wherein the spherical reflectors are spherically bent crystals.
14. The apparatus of claim 2 wherein the spherical reflectors are spherically bent mirrors.
15. The apparatus of claim 14 further comprising an aperture to select the rays that reach the image of the object.
16. The apparatus of claim 2 wherein the object is a mask.
17. The apparatus of claim 1 wherein the Bragg angles, θ 1 and θ 2 , are each less than 45 degrees.
18. The apparatus of claim 1 wherein the Bragg angles, θ 1 and θ 2 , are each greater than 45 degrees.
19. The apparatus of claim 1 wherein the Bragg angle θ 1 is smaller than 45 degrees and the Bragg angle θ 2 is larger than 45 degrees.
20. The apparatus of claim 1 wherein the Bragg angle pair and angle of rotation satisfies an aplanatic configuration for the spherical reflectors.
21. The apparatus of claim 2 wherein the Bragg angles, θ 1 and θ 2 , are each less than 45 degrees.
22. The apparatus of claim 2 wherein the Bragg angles, θ 1 and θ 2 , are each greater than 45 degrees.
23. The apparatus of claim 2 wherein the Bragg angle θ 1 is smaller than 45 degrees and the Bragg angle θ 2 is larger than 45 degrees.
24. The apparatus of claim 2 wherein the Bragg angle pair and angle of rotation satisfies an aplanatic configuration for the spherical reflectors.
25. An apparatus for forming an image of an object, the apparatus comprising: at least one pair of concentric spherical reflectors configured to reflect EUV rays wherein the reflectors share a common center and wherein each pair includes a convex reflector containing a radius of curvature R 1 and a Bragg angle θ 1 , and a concave reflector containing a radius of curvature R 2 and a Bragg angle θ 2 ; wherein the spherical reflectors are concentric with a mathematical sphere that contains a radius RT, wherein:
RT=R 1 cos(θ 1 )= R 2 cos(θ 2 ).
26. The apparatus of claim 25 wherein the Bragg angle pair and angle of rotation satisfies an aplanatic configuration for the spherical reflectors.