Method and apparatus for analyzing fluorine containing gases

A system for controlling the concentration of fluorine in an excimer laser gas during operation of an excimer laser to thereby stabilize the output power of the laser, the system comprising:

• a packed column comprising a compound which has no halogen atom and reacts with fluorine gas to form a solid halide and at least one of molecular oxygen and carbon dioxide, said solid halide being retained in said packed column;
• means for passing a sample of the laser gas extracted from the excimer laser through said packed column;
• a gas detecting means for measuring the concentration of said at least one of molecular oxygen and carbon dioxide in a gas flowing out of said packed column and producing an electrical signal representing the measured concentration of said at least one of molecular oxygen and carbon dioxide as an indication of the concentration of fluorine in the laser gas;
• arithmetic means for making a computing operation using said electrical signal to find a deviation of the concentration of fluorine in the laser gas from a predetermined concentration and producing a control signal representing an appropriate amount of supply of fluorine to the laser gas in the laser for cancellation of said deviation;
• and
• flow rate control means for regulating the supply of fluorine to the laser gas in the laser based on said control signal.

An apparatus for analyzing a mixed gas containing fluorine gas but not oxygen and carbon dioxide gases to determine at least the concentration of the fluorine gas, the apparatus comprising:

• a packed column comprising a compound which has no halogen atom and reacts with the fluorine gas to form a solid fluoride and at least one of molecular oxygen and carbon dioxide, said solid fluoride being retained in said packed column;
• means for passing the fluorine containing mixed gas through said packed column;
• a gas detecting means for measuring the concentration of said at least one of molecular oxygen and carbon dioxide in a gas flowing out of said packed column;
• and
• conversion means for converting the measured concentration of said at least one of molecular oxygen and carbon dioxide in the gas flowing out of said packed column to the concentration of fluorine gas in said mixed gas.

An apparatus for analyzing a mixed gas containing fluorine gas to determine at least the concentration of the fluorine gas, the apparatus comprising:

• a first packed column comprising a compound which has no halogen atom and reacts with fluorine gas to form a solid first fluoride and at least one of molecular oxygen and carbon dioxide, said solid first fluoride being retained in said first packed column;
• a packed column means which is substantially in parallel arrangement with said first packed column and comprises a material which reacts with fluorine gas to form a second solid fluoride without forming said at least one of molecular oxygen and carbon dioxide, said second solid fluoride being retained in said packed column means;
• means for passing said mixed gas alternately and selectively through either of said first and second packed columns while blocking the other of said first and second packed columns;
• a gas detecting means for alternately measuring the concentration of said at least one of molecular oxygen and carbon dioxide in a first gas flowing out of said first packed column and the concentration of said at least one of molecular oxygen and carbon dioxide in a second gas flowing out of said second packed column;
• and
• conversion means for subtracting the measured concentration of said at least one of molecular oxygen and carbon dioxide in said second gas from the measured concentration of said at least one of molecular oxygen and carbon dioxide in said first gas, thereby to determine a corrected concentration of said at least one of molecular oxygen and carbon dioxide formed in said first packed column and converting said corrected concentration to the concentration of fluorine gas in said mixed gas.