Method for purifying nitrogen trifluoride gas
AssigneeMitsui Toatsu Chemicals, Inc.
InventorsIsao Harada, Hisashi Hokonohara, Toshiaki Yamaguchi
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Abstract
NF.sub.3 gas containing N.sub.2 F.sub.2 as an impurity is purified by heating said NF.sub.3 gas at specified temperatures in a vessel the inner wall of which is coated with a strong and passive film of nickel flouride. According to this method, the rate of NF.sub.3 loss is low and the rate of removing N.sub.2 F.sub.2 is high. Therefore, when the NF.sub.3 gas thus purified is further purified with a known adsorbent, a highly pure NF.sub.3 gas can be easily and safely produced which is suitable for materials for semiconductor dry etching agents and the like.
Claims14
A method for purifying nitrogen trifluoride gas containing at least dinitrogen difluoride as impurities which comprises:
- a. providing a vessel at least the inner wall of which is composed of nickel;
- b. then forming a film of nickel fluoride by bringing at least fluorine gas into contact with for 10 minutes to 15 hours with the nickel inner wall of the vessel, the vessel being heated to about 30.degree. to 200.degree. C., said at least fluorine gas contacting the nickel inner wall first having a low F.sub.2 gas concentration and then being enhanced to finally having a 100 percent content of F.sub.2 gas;
- c. then heating the nitrogen trifluoride gas at 150.degree. to 600.degree. C. in the vessel the nickel inner wall of which is covered with the nickel fluoride film;
- and
- d. then heating the nickel fluoride film at 400.degree. to 800.degree. C. in an inert atmosphere.
A method for purifying nitrogen trifluoride gas containing at least dinitrogen difluoride as impurities which comprises:
- a. providing a vessel at least the inner wall of which is composed of nickel;
- b. then forming a film of nickel fluoride by bringing at least fluorine gas into contact for 10 minutes to 15 hours with the nickel inner wall of the vessel, the vessel being heated to about 30.degree. to 200.degree. C., said at least fluorine gas contacting the nickel inner wall first having a low F.sub.2 gas concentration and then being enhanced to finally having a 100 percent content of F.sub.2 gas;
- c. then packing the vessel with a solid fluoride, the nickel inner wall of the vessel being covered with the nickel fluoride film, to form a packed bed;
- d. then heating the nitrogen trifluoride gas in the packed bed at 150.degree. to 600.degree. C., and
- e. then heating the nickel fluoride film at 400.degree. to 800.degree. C. in an inert atmosphere.
Dependencies are inferred from the claim text.