Applying Q-type aspheres in the Ultraviolet Lithography Objective Lens

摘要

Ultraviolet lithography is the most important technology for the semiconductor manufacturer. The high resolution lithography objective lens is the key component of ultraviolet lithography. Aspheres are becoming more and more popular in optical design of lens systems. For traditional aspheres, non-zero terms of over 10th order are seldom used by optical designers. In the paper, we proposes a ultraviolet lithography objective lens with Q-type aspheres. The working wavelength is 193.368 nm, numerical aperture is 0.75, reduction ratio is 0.25, the thickness from the first lens to object is 60mm, the thickness from the last lens to image is 8.5mm, the total track length (from object to image) is 1186mm and image field of view is 26mm×10.5mm. The optical material in ultraviolet wave band is very few, only silica and CaF_2 can be used in engineering project. Because CaF_2 material is very expensive in cost, so we choose silica as the material of ultraviolet lithography objective lens. The ultraviolet lithography objective lens is consisted of twenty-three glass, the maximal aperture is 136.5mm eight aspheric surfaces are used to correct the off axis aberration and higher order aberration. We use the Q-type aspheres and traditional aspheres in the ultraviolet lithography objective lens, and compare the design results.