| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fluoride single crystal whose section cut perpendicularly to the direction of the crystal-growing axis has a diameter of ≥50 mm and which offers a sufficient resolution performance when used as a stepper lens material, a method for growing the fluoride single crystal, and a lens made of the fluoride single crystal. <P>SOLUTION: In the fluoride single crystal, the section cut perpendicular to the direction of the crystal-growing axis A has a nearly circular shape and a diameter of ≥50 mm, and a value (ΔT2-ΔT1) satisfies the relation: 0≤(ΔT2-ΔT1)≤0.25, wherein ΔT1 is the difference between transmittance before and after ArF laser irradiation [(transmittance before irradiation-transmittance after irradiation) both measured at a wavelength of 193 nm] at the center C and ΔT2 is the difference between transmittance before and after ArF laser irradiation [(transmittance before irradiation-transmittance after irradiation) both measured at a wavelength of 193 nm] at the periphery O of the section, respectively. The method is for growing the fluoride single crystal. The lens is made of the fluoride single crystal. <P>COPYRIGHT: (C)2007,JPO&INPIT |
