Synthetic fused silica member

Abstract

There is disclosed a synthetic fused silica member used at a wavelength of 200 nm or less which has a hydroxyl group-content of 1 to 50 ppm and a fluorine-content of 100 to 1000 ppm, and contains no chlorine, and has a birefringence of the synthetic fused silica member of 2 nm/cm or less. The synthetic fused silica member can be used as a synthetic fused silica substrate for photomask, or in an optical system wherein a fluorine excimer laser is used as a light source. There can be provided a synthetic fused silica member which can efficiently transmit a light having a wavelength as 200 nm or less, especially fluorine excimer laser (157 nm), and does not suffer from lowering of transmittance due to damage.

Dependencies are inferred from the claim text.