To rinse out the closed interior of a projection lens, for semiconductor lithography, the interior is flushed with a mixture of inert gases with a refractive index matching the refractive index of air

摘要

To rinse out at least one closed interior (4) of a lens (1), a mixture is used of at least two inert gases, where their refractive index matches the refractive index of air. To rinse out a closed interior zone, of a lens, the air or synthetic air has 78-80 vol.% nitrogen (N2) and 20-22 vol.% oxygen (O2). The lens is a projector lens for semiconductor lithography. The second inert gas in the mixture is a noble gas e.g. helium, krypton, or xenon. The nitrogen is present with 95-99 vol.% and the helium is at 0.5-5.0 vol.% or 1.1-1.3 vol.% and preferably 1.2 vol.%. An Independent claim is included for a lens rinsing process, where a mixture of at least two inert gases is fed into the closed interior through at least one inlet drilling (5a), and is extracted through at least one outlet drilling (5b).