Patent Number: 062263463
Section: claims

1. A scanning ring field lithography apparatus for patterning images on a substrate comprising: a radiation source emitting extreme ultraviolet radiation of wavelengths ranging from approximately 4 to 20 nanometers;  a reflective mask for generating patterned images at the substrate;  reflective focusing optics positioned between the mask and the substrate, comprising four reflective elements which listed from mask to substrate are characterized as convex, concave, convex and concave, arranged such that the convex first reflective element is positioned in closer proximity to the substrate than the convex third reflective element, wherein the reflective focusing optics project a focused image on and telecentric at the substrate in the shape of an arcuate slit having a width between approximately 0.5-3.0 mm, and wherein the reflective focusing optics are characterized by a balanced static centroid distortion curve across the width of the arcuate slit and a numerical aperture of at least about 0.1.  a radiation source emitting extreme ultraviolet radiation of wavelengths ranging from approximately 4 to 20 nanometers;  a reflective mask for generating patterned images at the substrate;  reflective focusing optics positioned between the mask and the substrate comprising: 2. The apparatus of claim 1, wherein at least three of the four reflective elements of the reflective focusing optics are rotationally symmetric aspheric surfaces. 3. The apparatus of claim 1, wherein the first reflective element deviates from the best fitting spherical surface by 8.8 .mu.m.+-.2.0 .mu.m, the second reflective element deviates from the best fitting spherical surface by 11.7 .mu.m.+-.2.0 .mu.m, and the fourth reflective element deviates from the best fitting spherical surface by 4.7 .mu.m.+-.2.0 .mu.m. 4. The apparatus of claim 1, wherein the four reflective elements of the reflective focusing optics are rotationally symmetric aspheric surfaces. 5. The apparatus of claim 4, wherein the first reflective element deviates from the best fitting spherical surface by 8.8 .mu.m.+-.2.0 .mu.m, the second reflective element deviates from the best fitting spherical surface by 11.7 .mu.m.+-.2.0 .mu.m, the third reflective element deviates from the best fitting spherical surface by 0.16 .mu.m.+-.1.0 .mu.m, and the fourth reflective element deviates from the best fitting spherical surface by 4.7 .mu.m.+-.2.0 .mu.m. 6. The apparatus of claim 1, wherein each optical element of the reflective focusing optics has a reflective multilayer coating in which each layer has a substantially uniform thickness. 7. The apparatus of claim 1, wherein the reflective focusing optics are positioned such that a beam of the extreme ultraviolet radiation has a mean incidence angle upon the first reflective element of about 3.5.degree..+-.10.degree., a mean incidence angle upon the second reflective element of about 6.6.degree..+-.10.degree., a mean incidence angle upon the third reflective element of about 12.degree..+-.10.degree. and a mean incidence angle upon the fourth reflective element of about 6.0.degree..+-.10.degree.. 8. The apparatus of claim 1, wherein the reflective optical elements are coaxial with respect to each other. 9. The apparatus of claim 1, wherein an aperture stop is accessibly located at or near the third reflective element. 10. The apparatus of claim 9, wherein the reflective focusing optics have an optical axis, and wherein the third reflective element is located on the optical axis. 11. The apparatus of claim 9, wherein the aperture stop is centered on the optical axis of the reflective focusing optics. 12. An optical system for use with a scanning ring field lithography apparatus, comprising: 13. The optical system of claim 12, wherein the at least one convex reflective element is a rotationally symmetric surface. 14. The optical system of claim 12, wherein the at least one concave reflective element is a rotationally symmetric surface. 15. The optical system of claim 12, wherein the at least one convex reflective element deviates from the best fitting spherical surface by less than approximately 11 .mu.m. 16. The optical system of claim 12, wherein the at least one concave reflective element deviates from the best fitting spherical surface by less than approximately 14 .mu.m. 17. The optical system of claim 12, wherein the at least one convex reflective element and the at least one concave reflective element have a reflective multilayer coating in which each layer has a substantially uniform thickness. 18. The optical system of claim 12, wherein the at least one convex reflective element and the at least one concave reflective element are coaxial with respect to each other.