PROJECTION LENS FOR MICROLITHOGRAPHY AND CORRESPONDING TERMINAL ELEMENT
The invention relates to a projection lens ( 5 ) for microlithography, in particular, for immersion lithography, designed to operate at a wavelength of more than 190 nm and comprising an optical element made from quartz glass with an OH content of less than 50 ppm, in particular between 10 ppm and 50 ppm, and a water content of between 1.5×10 16 and 2×10 18 molecules/cm 3 , preferably between 2×10 16 and 1×10 18 molecules/cm 3 , in particular between 5×10 16 and 2×10 17 molecules/cm 3 . The optical element is preferably a terminal element ( 14 ) for the projection lens ( 5 ) in a microlithography projection illumination unit ( 1 ) for immersion lithography.
1 - 13 . (canceled)
14 . A projection lens for microlithography designed for an operating wavelength of more than 190 nm, comprising at least one optical element made of silica glass, wherein the silica glass comprises an OH content of less than 5 ppm, a hydrogen content of between 1.5×10 16 and 2×10 18 molecules/cm 3 , and a fluorine content of less than 50 ppm.
15 . The projection lens according to claim 14 , in which the SiH content of the silica glass is minimized.
16 . The projection lens according to claim 14 , in which the silica glass is cold-charged with hydrogen.
17 . The projection lens according to claim 14 , in which the change dk sat /dH in the saturation value k sat of the absorption coefficient of the silica glass depending on the energy density H is less than 1×10 −4 cm/mJ.
18 . The projection lens according to claim 14 , in which the optical element during operation of the projection lens at the operating wavelength, at least in partial regions, is subjected to a pulse energy density of between 200 μJ/cm 2 and 1000 μJ/cm 2 .
19 . The projection lens according to claim 14 , in which the optical element is arranged near the focal plane of the projection lens.
20 . The projection lens according to claim 14 , in which the optical element is an end element of the projection lens.
21 . The projection lens according to claim 14 , in which the projection lens preserves the degree of polarization of incident radiation to more than 80%.
22 . An end element for a projection lens made of silica glass, in which the silica glass comprises an OH content of less than 5 ppm and a fluorine content of less than 50 ppm.
23 . The end element according to claim 22 , in which the silica glass comprises a hydrogen content of between 1.5×10 16 and 2×10 18 molecules/cm 3 .
24 . A microlithography projection exposure apparatus comprising a projection lens designed for an operating wavelength of more than 190 nm and an end element according to claim 22 , wherein an immersion liquid is arranged between the end element and a light-sensitive substrate.