Abstract: Carbon members contaminated with deposits of metals and/or metal compounds such as nitrides or carbides are thoroughly cleaned with little adverse influences on the carbon members themselves by treating the contaminated carbon members with a cleaning gas consisting of 1-20 vol % of CIF.sub.3 gas and the balance of an inactive diluent gas at a temperature in the range from 200.degree. to 300.degree. C. For example, this cleaning method is applicable to graphite parts of apparatus for forming thin films in the manufacture of semiconductor devices.

Abstract: The invention provides a selective adsorption method for refining NF.sub.3 gas containing CF.sub.4 as impurity. At a temperature not higher than 10.degree. C. the NF.sub.3 gas is brought into contact with a crystalline and porous synthetic zeolite, which is substantially uniform in pore size and about 4.9 .ANG. in effective pore size and is commerciallized under the name of molecular sieve 5A, on condition that the content of water of crystallinity in the synthetic zeolite is 1-10 wt. %, and preferably 6-10 wt. %. The synthetic zeolite efficiently adsorbs NF.sub.3 with little adsorption of CF.sub.4.