Detection of low lead impurity level in transmitting optical fluoride crystal for manufacturing integrated circuit chips, by measuring transmission test wavelength through optical fluoride crystal light transmission path length

摘要

A low lead impurity level in a below 200 nm transmitting optical fluoride crystal is determined by transmitting a transmission test wavelength of 200-210 nm through below 200 nm wavelength transmitting optical fluoride crystal light transmission path length and measuring the transmission of the 200-210 nm test wavelength to provide a lead ppb impurity level measurement less than 900 ppb. Detection of a low lead impurity level in a below 200 nm transmitting optical fluoride crystal, comprises providing a below 200 nm wavelength transmitting optical fluoride crystal (20) having a crystal light transmitting path length (21). The below 200 nm wavelength transmits optical fluoride crystal light transmission path length =2 mm. A light transmission spectrophotometer is provided having a lamp for producing a transmission test wavelength of 200-210 nm and a transmission detector (28) for measuring transmission of the test wavelength. The transmission test wavelength of 200-210 nm is transmitted through below 200 nm wavelength transmitting optical fluoride crystal light transmission path length and measuring the transmission of the 200-210 nm test wavelength through the path length to provide a lead ppb impurity level measurement less than 900 ppb. An independent claim is also included for a method of making a below 200 nm wavelength optical element having an absorption coefficient at 200-210 nm of less than 0.0017 cm-1.