Langmuir probe and optical emission studies of Ar, O2, and N2 plasmas produced by an electron cyclotron resonance microwave source

An understanding of electron cyclotron resonance microwave plasma discharges requires the measurement of plasma parameters. In argon, nitrogen and oxygen plasmas, cylindrical Langmuir probes were used to determine the variations of plasma parameters (ion density Ni, floating potential Vf, plasma potential Vp, and electron temperature Te) with applied power (100–300 W) and pressures (1–10×10−4 Torr). Simultaneous optical emission (OE) spectra were also obtained, and, using knowledge of excited and neutral peak intensities and transition energies, the electron temperatures were calculated. By the use of the Langmuir probe electron temperature results, the electron temperatures obtained from OE resulted in scaling factors C of 2, 0.15, and 2 eV−0.75 for argon, oxygen, and nitrogen, respectively.