Projection lithography photomask blanks, preforms and method of making

摘要

The invention includes methods of making lithography photomask blanks. The invention also includes lithography photomask blanks and preforms for producing lithography photomask. The method of making a lithography photomask blank includes providing a soot deposition surface, producing SiO2 soot particles and projecting the SiO2 soot particles toward the soot deposition surface. The method includes successively depositing layers of the SiO2 soot particle on the deposition surface to form a coherent SiO2 porous glass preform body comprised of successive layers of the SiO2 soot particles and dehydrating the coherent SiO2 glass preform body to remove OH from the preform body. The SiO2 is exposed to and reacted with a fluorine containing compound and consolidated into a nonporous silicon oxyfluoride glass body with parallel layers of striae. The method further includes forming the consolidated silicon oxyfluoride glass body into a photomask blank having a planar surface with the orientation of the striae layer parallel to the photomask blank planar surface.