| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for tempering to obtain a single crystal having excellent optical characteristics such as refractive index uniformity or stress birefringence in a (100) or (110) direction of the single crystal and free from stress in the manufacture of a calcium fluoride single crystal to be used for microlithography at short wavelength of≤250 nm, preferably≤193 nm, and to provide a calcium fluoride crystal and an integrated circuit and an electronic device using the above crystal. SOLUTION: The method includes, for the purpose of tempering a crystal, steps of: (a) heating the crystal to 1,000°C to 1,350°C at less than 18 K/h heating rate; (b) holding the crystal at the heating temperature of the step (a) for at least 65 hours to control the temperature difference in the crystal to maximum 0.2K; (c) cooling the crystal to a temperature range above a limiting temperature between 900°C and 600°C at maximum 0.5 K/h cooling rate; and (d) cooling the crystal at maximum 3 K/h cooling rate to a temperature further below the above temperature range. COPYRIGHT: (C)2005,JPO&NCIPI |
