HIGH-INDEX UV OPITCAL MATERIALS FOR IMMERSION LITHOGRAPHY

摘要

This invention is related to material for use as an ultraviolet (UV) optical element and particularly for use as a 193 nm immersion lens element. The material for use as a UV optical element includes a Lithium Magnesium Aluminate (LMAO) body. The specific compound for this application is the disordered lithium magnesium spinel, having the general composition of Li<SUB>x</SUB>Mg<SUB>2(1-x)</SUB>AI<SUB>4+x</SUB>O<SUB>8</SUB> where x = 0 to 1 as the high-index UV transparent material for immersion lithography. The LMAO body may include a disordered spinel, such as, for example, a single crystal that may be cubic in symmetry, optically isotropic, and having cation disorder within the structure to reduce the intrinsic birefringence (IBR). The LMAO body has certain desired material properties and may be readily made in relatively large sizes suitable for use as the UV optical element for photolithography.