Nikon F2 exposure tool development

Present status of development of F2 (157nm) exposure tool in Nikon is described. Key points of F2 exposure tool are reported; low aberration projection optics, CaF2 quality, coating durability and gas purging of the pellicle space. We also report the measurement of refractive index inhomogeneity inside CaF2 crystals, which is suspected as the cause of local flare. Characteristics of high NA optics over 0.9 are investigated by imaging simulations for both 193nm and 157nm wavelengths, which are compared NA=0.85 imaging.