Non-invasive optical emission diagnostic to determine plasma parameters in oxygen discharges

An emission model has been developed to exploit the relative spectral intensities of oxygen discharge emissions to non-invasively determine plasma properties. The emission model employs electron-temperature dependent rates for electron-impact excitation from the ground states of O, O₂ and O₂⁺. For O₂⁺ ions, excitation rates and the effect of quenching of excited states via electron collisions have been characterized by fitting relative emission intensities over a range of discharge pressures and powers for which electron density and temperature were independently measured. Outputs of the emission model are the electron temperature and the oxygen dissociation fraction. Implementation and validation of the emission model is in progress using an extensive set of measurements taken, including O and O₂⁺ relative emission intensities (optical emission spectroscopy (OES)), gas temperature (OES), electron density (multipole resonance probe), dissociation fraction (actinometry) and electron temperature (Langmuir probe). Results will be presented for an oxygen inductively coupled plasma for pressures of 1 to 30 mTorr and discharge powers in the range of 250 to 2000 watts.