Characterization of a low-pressure argon plasma using optical emission spectroscopy and a global model

Abstract

The excitation mechanisms of the lower lying excited levels in a low-ionized, low-pressure, argon plasma are modeled and studied in order to characterize the plasma through optical emission spectroscopy. It is found that the lower lying excited states of argon play an important role in the excitation and that they must be taken explicitly into account for an accurate determination of the excitation rates. The possible influence of radiative cascades from upper argon excited states, which are not included in the model, has been studied by introducing an effective level in the description and studying its influence on the results. The model has been used to calculate the electron density and electron temperature in an argon magnetron sputtering plasma produced at different electromagnetic powers and gas pressures, as a function of the intensity of the optical emission lines λ1=750.38nm and λ2=696.54nm. The results obtained from the model have been compared with Langmuir probe measurements, showing a good agreement. It is hereby demonstrated that optical emission spectroscopy can be used to monitor the plasma properties during the deposition process when applying a nonlinear model.