Mass spectrometer, use thereof, and method for the mass spectrometric examination of a gas mixture

An apparatus, comprising:

• a mass spectrometer, comprising:
• an ionization device;
• and
• an ion trap configured to store and mass spectrometrically examine a gas mixture,
• wherein:
• the ionization device is configured to supply:
• a) ions to the ion trap to ionize the gas mixture;
• b) metastable particles of an ionization gas to the ion trap to ionize the gas mixture;
• and/or b) electrons to the ion trap to ionize the gas mixture;
• the mass spectrometer is configured to determine the number of:
• a) ions present in the ion trap;
• b) metastable particles of the ionization gas present in the ion trap;
• and/or b) ions of a residual gas present in the ion trap prior to examining the gas mixture;
• and
• the apparatus is an EUV lithography apparatus.

A method, comprising:

• using, in an EUV lithography process, a mass spectrometer to mass spectrometrically examine a gas mixture,
• wherein:
• the mass spectrometer, comprises:
• an ionization device;
• and
• an ion trap configured to store and mass spectrometrically examine a gas mixture;
• the ionization device is configured to supply:
• a) ions to the ion trap to ionize the gas mixture;
• b) metastable particles of an ionization gas to the ion trap to ionize the gas mixture;
• and/or b) electrons to the ion trap to ionize the gas mixture;
• and
• the mass spectrometer is configured to determine the number of:
• a) ions present in the ion trap;
• b) metastable particles of the ionization gas present in the ion trap;
• and/or b) ions of a residual gas present in the ion trap prior to examining the gas mixture.