Development of dioptric projection lenses for deep ultraviolet lithography at Carl Zeiss

Advanced dioptric projection lenses from Carl Zeiss are used in some of the world's most advanced deep ultraviolet projection lithography systems. These lenses provide a resolution of better than 100 nm across the entire field of view with a level of aberration control that maximizes critical dimension uniformity and lithographic process latitude. These dioptric projection lenses are currently being used for critical layer device patterning for a wide array of complex logic, memory, and application specific integrated circuits. Zeiss' involvement in the development of ultraviolet lenses goes back to the year 1902, more than 100 years ago, when von Rohr calculated the first monochromatic ultraviolet microobjectives for ultra-high-resolution microphotography using a line-narrowed source. The modern dioptric projection lenses for lithography are influenced by the collective experience in the field of microscopy, and the more recent experience with early step-and-repeat lenses. We discuss some of the foundations of modern dioptric designs in the context of this history, demonstrating that rapid synthesis of designs is possible using combinations of monochromatic microscope objectives and early step-and-repeat lenses from the 1970s. The problems associated with ultrahigh numerical aperture objectives are discussed. Specifically, it is demonstrated that aspheres can be used effectively to reduce the volume of full field projection lenses, making the mechanical implementation of a 0.90 NA lens feasible in production. Several contemporary dioptric projection lens designs are reviewed in detail. The extension of these designs to numerical apertures greater, than 1.0 using immersion techniques is demonstrated. These immersion lenses give the potential for 40-nm resolution. (C) 2004 Society of Photo-Optical Instrumentation Engineers.