System for flushing inner chambers of lens used in semiconductor lithography comprises using mixture of at least two inert gases so that resulting refractive index corresponds to refractive index of air

摘要

A system for flushing the inner chambers (4) of a lens (1) used in semiconductor lithography, in which the lens is gas-tight to the surroundings, comprises using a mixture of at least two inert gases so that the resulting refractive index corresponds to the refractive index of air. Preferred Features: The inert gases used are nitrogen in an amount of 95-99 vol.% and helium in an amount of 1-5, preferably 1.2 vol.%