PROBE DIAGNOSTICS OF NON-MAXWELLIAN PLASMAS

Various probe diagnostic methods have been applied to rf plasmas with non-Maxwellian electron energy distribution functions (EEDF) and the r esults of these diagnostic methods have been compared. Plasma density and electron temperature were obtained using standard procedures from the electron retardation region (classic Langmuir method), the ion sat uration region, and the electron saturation region of the measured pro be I/V characteristic. Measurements were made in a 13.56-MHz capacitiv e argon rf discharge at two gas pressures: p=0.03 Torr, where stochast ic electron heating is dominant, and p=0.3 Torr, where collisional ele ctron heating dominates. Thus, the measured EEDF at each gas pressure manifests a distinct departure from thermodynamic equilibrium being bi -Maxwellian at 0.03 Torr and Druyvesteyn-like at 0.3 Torr. Considerabl e differences in electron density and temperature were obtained from t he different parts of the probe characteristic and these values differ dramatically in many cases from those found from integration of the m easured EEDF's, thus demonstrating that using standard procedures in n on-Maxwellian plasma can give misleading results.