| 摘要 |
An object of the present invention is to provide a fluoride crystal having a high transmittance with respect to an excimer laser and an excellent resistance with respect to a high output laser, and a production method thereof. The fluoride crystal of the present invention contains at least one kind of atom selected from the group consisting of Zn, Cd, Pb, Li, Bi and Na with a content of 10 ppm or less, and having an internal transmittance of 70% or more with respect to a 135 nm wavelength light. The method of the present invention of producing a fluoride crystal comprises conducting a refining step of adding a scavenger to a calcium fluoride raw material and refining the raw material at least once, and a crystal growth step of further adding the scavenger to the refined raw material and growing a crystal by using a crucible lowering method, wherein the amount of the scavenger to be added in the first refining step is 0.04 to 0.1 mol % based on the raw material, and the total amount of the scavenger to be added in the subsequent refining steps and the crystal growth step is 10% to 50% based on the amount of the scavenger to be added in the first refining step. <IMAGE> |
