METHOD OF REFINING RARE GAS FLUORIDE EXCIMER LASER GAS

摘要

A laser gas used in a rare gas fluoride excimer laser is efficiently refined with little loss of the principal rare gas such as Ar, Kr or Xe by sequential contact of the laser gas first with a reactive metal, e.g. Si or Fe, for conversion of the fluorine source gas such as F2 or NF3 to a metal fluoride, then with a solid alkaline compound, e.g. Ca(OH)2, for conversion of gaseous fluorides to solid metal fluorides, next with zeolite which is adsorbent of most of the remaining impurities and finally with an alkaline metal, e.g. Ca or Na, for decomposition of CF4 to form a solid metal fluoride and carbon. CF4 is formed during operation of the excimer laser by reaction of fluorine with a fluororesin used as electrical insulator in the laser apparatus, and accumulation of CF4 in the laser gas causes significal lowering of the laser output power.