Silica glass optical material for projection lens to be utilized in vacuum ultraviolet radiation lithography, method for producing the same, and projection lens
AssigneesHeraeus Quarzglas GmbH & Co. KG, Shin-Etsu Quartz Products Co., Ltd.
InventorShigeru Yamagata
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Abstract
A silica glass optical material for projection lens to be used in vacuum ultraviolet radiation lithography using radiation from 155 to 195 nm in wavelength, wherein, said silica glass optical material is of ultrahigh purity, contains from 1 to 10 wtppm of OH groups, from 100 to 10,000 wtppm of F, and from 1×1017 to 1×1019 molecules/cm3 of H2, and has a distribution in concentration of F that is axially symmetrical to the central axis.
Claims25
A silica glass optical material for projection lens to be used in vacuum ultraviolet radiation lithography using radiation from 155 to 195 nm in wavelength, wherein, said silica glass optical material is of ultrahigh purity, contains from 1 to 10 wtppm of OH groups, from 100 to 10,000 wtppm of F, and from 1×1017 to 1×1019 molecules/cm3 of H2, and has a distribution in concentration of F that is axially symmetrical to the central axis, wherein the material is of ultrahigh purity as such containing 1 wtppm or less each of Li, Na, and K, 0.5 wtppb or less each of Ca and Mg, and 0.1 wtppb or less each of Cr, Fe, Ni, Mo, and W.
A silica glass optical material for projection lens to be used in vacuum ultraviolet radiation lithography using radiation from 155 to 195 nm in wavelength, wherein, said silica glass optical material is of ultrahigh purity, contains from 1 to 10 wtppm of OH groups, from 100 to 10,000 wtppm of F, and from 1×1017 to 1×1019 molecules/cm3 of H2, and has a distribution in concentration of F that is axially symmetrical to the central axis, wherein the amount of strain is not more than 1 nm/cm.
In a method for producing a silica glass optical material for projection lens to be used in vacuum ultraviolet radiation lithography using radiations from 155 to 195 nm in wavelength, wherein said silica glass optical material is of ultrahigh purity, contains from 1 to 10 wtppm of OH groups, from 100 to 10,000 wtppm of F, and from 1×1017 to 1×1019 molecules/cm3 of H2, and has a distribution in concentration of F that is axially symmetrical to the central axis, wherein the material is of ultrahigh purity as such containing 1 wtppm or less each of Li, Na, and K, 0.5 wtppb or less each of Ca and Mg, and 0.1 wtppb or less each of Cr, Fe, Ni, Mo, and W,
- said method for producing a silica glass optical material comprising:
- producing a white colored soot body having an approximately cylindrical shape and containing OH groups by means of flame hydrolysis of a silicon compound,
- performing fluorine doping treatment to the resulting soot body by subjecting it to a heat treatment in a fluorine-containing gaseous atmosphere to obtain a soot body containing OH groups and fluorine,
- vitrifying the resulting body to obtain a transparent body by heating it in a reduced pressure atmosphere,
- performing zone melting rotary stirring treatment by flame heating sequentially said transparent glass body from one end portion to the other end portion to thereby realize a distribution in fluorine concentration as such to be symmetrical to the rotation axis,
- preparing a molding frame having a cylindrical molding cavity,
- melting and molding said transparent glass body into an approximately cylindrical shape by placing said glass body inside said molding frame in such a manner that the rotation axis may be superposed to the central axis of said molding frame,
- removing strain by annealing treatment, and finally
- performing gaseous hydrogen doping by applying heat treatment in a gaseous atmosphere containing hydrogen molecules.
Dependencies are inferred from the claim text.