US Patent 11430643 Quantification of processing chamber species by electron energy sweep

A plasma processing system includes a plasma chamber configured to contain a plasma, a shutter chamber fluidically coupled to the plasma chamber via a first orifice, a mass spectrometer fluidically coupled to the shutter chamber, and a shutter disposed in the shutter chamber between the first orifice and the mass spectrometer in the path of a particle beam. The first orifice is configured to generate the particle beam from the plasma using a pressure differential between the shutter chamber and the plasma chamber. The mass spectrometer includes an ionizer configured to ionize species of the particle beam by sweeping through a range of electron energies in a plurality of energy steps. The shutter is configured to open and close during each of the plurality of energy steps.