Parametric study on excitation temperature and electron temperature in low pressure plasmas

This work aims at investigation of the validity of the electron excitation temperature (Texc) by optical emission spectroscopy (OES) as an alternative diagnostic to the electron temperature (Te). The excitation and the electron temperatures were measured at a wide range of gas pressures and input powers in different plasmas such as capacitively-coupled, inductively-coupled, and magnetron direct current plasmas. As a result, both temperatures were found to decrease with an increase in pressure, whereas they not very dependent on power, indicating that Texc showed a tendency identical to that of Te as pressure and power were varied. This result suggests that Texc measurement can be an alternative diagnostic for Te measurement once the ratio of the two temperatures is found in advance through a calibration experiment especially for low pressure high electron density industrial processing plasmas in which probe measurements are limited.