Patent attributes
A projection objective for imaging a pattern arranged in an object surface of the projection objective onto an image surface of the projection objective using ultraviolet radiation has a plurality of optical elements including transparent optical elements transparent for radiation at an operating wavelength λ, where 260 nm>λ>150 nm, an image-side pupil surface arranged between the object surface and the image surface, and an aperture-defining lens group arranged between the image-side pupil surface and the image surface for converging radiation coming from the image-side pupil surface towards the image surface to define an image-side numerical aperture NA, where 0.7≦NA≦1.4. The aperture-defining lens group includes at least one high-index lens made from a transparent high-index material having a refractive index nHI, where nHI>nSIO2 and where nSIO2 is the refractive index of silicon dioxide (SiO2) at the operating wavelength.
