Patent Number: 054882290
Section: claims

1. A high resolution, deep UV beam photolithography system comprising a deep UV radiation source for generating a beam of deep ultraviolet radiation along a path, mask receiving structure in said path, a first optical system in said path for homogenizing and shaping the deep UV energy in said path; and a second optical system in said path for directing radiation energy onto the surface of a substrate to be processed, said second optical system including large area mirror structure having a numerical aperture of at least 0.3 and a plurality of refractive elements disposed between said mask receiving structure and said substrate for compensating (reducing) image curvature introduced into the system by said large area mirror structure, said second optical system providing a focal point outside any one of said refractive elements. 2. The system of claim 1 wherein all of the refractive elements in said second optical system are of fused silica. 3. The system of claim 1 wherein said deep UV radiation source is a laser of wavelength in the 150-250 nanometer range. 4. The system of claim i wherein said large area mirror structure includes a first mirror that is disposed on the system axis and a second mirror of concave spherical configuration with an aperture portion disposed on said beam path for passing a beam of radiation to said first mirror. 5. The system of claim 4 wherein each of said mirrors is mounted on a refractive lens component and includes a clear region on said beam path. 6. The system of claim 1 wherein said system is a microlithography system with a numerical aperture of about 0.6. 7. The system of claim 1 wherein said second optical system includes a plurality of lens elements (42-50) and first and second lens-mirror combinations (54, 56; 60, 62) that have the following dimensional values: 8. The system of claim 1 and further including optics for allowing an operator to view the imaging process in focus at a visible wavelength while substrate processing at an ultraviolet wavelength is in focus and is in progress. 9. The system of claim 1 wherein said refractive elements provide field flattening improvement of at least five times. 10. The system of claim 9 wherein all of the refractive elements in said second optical system are of fused silica. 11. The system of claim 9 wherein said deep UV radiation source is a laser of wavelength in the 150-250 nanometer range. 12. The system of claim 9 wherein said large area mirror structure includes a first mirror that is disposed on the system axis and a second mirror of concave spherical configuration with an aperture portion disposed on said beam path for passing a beam of radiation to said first mirror. 13. The system of claim 12 wherein said second mirror is mounted on a refractive lens component and includes a clear region on said beam path. 14. The system of claim 13 wherein said second optical system includes a plurality of lens elements (42-50) and first and second lens-mirror combinations (54, 56; 60, 62) that have the following dimensional values: 15. The system of claim 1 and further including optics for allowing an operator to view the imaging process in focus at a visible wavelength while substrate processing at an ultraviolet wavelength is in focus and is in progress. 16. For use in a deep ultraviolet microlithography system a reflective imaging system comprising first and second mirrors, at least fifty percent of the magnification or imaging power on the fast speed end of the system being provided by said mirrors, and  field flattening and aberration compensation structure including an array of lens elements, said array of lens elements all being formed from the same refractive material type and providing a focal point outside of said array of lens elements,  comprising a first plurality of lens elements disposed at a first predetermined position along an optical path of said imaging system for providing aberration compensation,  a second lens element disposed at a second predetermined position along said optical path subsequent to said first lens element, said second lens element being operative to act in conjunction with said mirrors to provide field flattening, and  a supplemental lens element disposed at a third predetermined position along said optical path for providing color compensation. 17. The system of claim 16 wherein said same refractive material type is fused silica. 18. The system of claim 16 wherein said imaging system and said compensation structure includes a plurality of lens elements (42-50) and first and second lens-mirror combinations (54, 56; 60, 62) that have the following dimensional values: 19. The system of claim 17 wherein each of said first and second mirrors is mounted on refractive lens components.