Patent ID: 6758063
Filing Date: 2004-07-06
Classification: C03C,G03F

Abstract:
A method of making a lithography photomask blank having a longest dimension length L, comprising the steps of:providing a fused silica SiO2 glass preform disk having a preform disk diameter D and a preform disk height H with D>H, said diameter D lying in a plane defined by a preform disk x-axis and a preform disk y-axis, said x-axis and said y-axis oriented normal to said disk height H, said disk height H in alignment with a preform disk z-axis, identifying an inclusion free region said inclusion free region free of inclusions having a diameter greater than 1 &mgr;m, maintaining the preform disk x-axis, y-axis and z-axis orientation while removing the inclusion free region from said preform disk to provide a photomask blank preform having a photomask blank preform x-axis, said photomask blank preform x-axis in alignment with said preform disk x-axis, a photomask blank preform y-axis, said photomask blank preform y-axis in alignment with said preform disk y-axis, and a photomask blank preform z-axis, said photomask blank preform z-axis in alignment with said preform disk z-axis and forming said photomask blank preform into a lithography photomask blank having a longest dimension length L, wherein the photomask blank preform has a birefringence &lE;2 nm/cm, and a fictive temperature of about 1050Â±50Â° C.