Patent ID: 6265115
Filing Date: 2001-07-24
Classification: C03B,C03C,G03F

Abstract:
A method of making a lithography photomask blank, comprising the steps of:providing a soot deposition surface,producing a plurality of SiO.sub.2 soot particles and projecting said SiO.sub.2 soot particles towards said soot deposition surface,successively depositing layers of said SiO.sub.2 soot particles on said deposition surface to form a coherent SiO.sub.2 porous glass preform body comprised of a plurality of successive SiO.sub.2 soot particle layers,dehydrating said coherent SiO.sub.2 glass preform body to remove OH from said coherent SiO.sub.2 glass preform body,exposing said SiO.sub.2 to a fluorine containing atmosphere and consolidating the coherent SiO.sub.2 glass preform body into a silicon oxyfluoride glass body having less than 1.times.10.sup.17 H.sub.2 molecules/cm.sup.3 and a plurality of parallel layers of striae,forming said consolidated silicon oxyfluoride glass body into a photomask blank having less than 1.times.10.sup.17 H.sub.2 molecules/cm.sup.3 and a planar surface with said parallel layers of striae parallel to said photomask blank planar surface.