Optical design studies concerning DUV lenses concentrated on investigations of the tracklength of the lens, chromatic problems and UDOF behaviour. Mechanical studies dealt with the stability problems that occur when fitting lens elements with diameters up to 250 mm into their mechanical mountings. Results of mechanical studies gained through cooperation with the subcontractor Philips CFT were used for the mechanical design of the prototype lens. A new mounting technique has been developed. The design of the prototype illumination system has been completed, and two prototypes delivered to ASM-L. Studies on the principles of DUV illumination systems concentrated on problems of field illumination, coherence and efficiency.
Further work has to be done to improve reliability and uniformity of illumination.
The feasibility studies on the lens mounting and mechanical lay-out have been carried out. Satisfactory solutions have been found to deal with future lenses with lengths up to 1000 mm and weights up to 150 kg. Within the Subsystem Adaptations task, various designs have been studied for both the reticle table and the focus sensor. Accuracy budgets estimates have been made for different stepper subsystems, supported by vibration studies. The mechanical design and vibration sensitivity of the stepper have been tested.