Ion and neutral argon temperatures in electron cyclotron resonance plasmas by Doppler broadened emission spectroscopy

Neutral and ionic gas temperatures (Tn and Ti) are crucial parameters in the plasma processing of materials (etching and film deposition). Here we evaluate a method used for obtaining the temperatures, i.e., the Doppler broadening, of emission lines. We focus on Ar lines from microwave electron cyclotron resonance plasmas. We use the same technique for both ions and neutrals. Three factors are important in achieving accuracy: (1) knowing the correct instrument width at the central wavelength of each ion and neutral line, (2) understanding the noise-dependent variation in the measured widths, and (3) knowing how the magnetic field affects the spectra. We find that T can be determined to within ∼100 °C. Ti and Tn are typically found to be ∼0.5 and <0.1 eV, respectively for 0.5 mTorr Ar.