INVESTIGATION OF EEDF AND ELECTRON DENSITY AND TEMPERATURE BY DEVELOPED LANGMUIR PROBE IN RF-CCP ARGON DISCHARGE AND CORRELATION WITH OES

Abstract

The Langmuir probe, which was introduced for the first time by Langmuir and Mott-Smith [1], is a powerful mean for measuring the plasma parameters in low-pressure discharges. It allows a direct, local and absolute measurement of all plasma parameters (electron density and temperature, floating and plasma potential, and energy electron distribution function (EEDF). A single rf-compensated cylindrical Langmuir probe has been developed in order to characterise a plasma RF discharge. Compensated measurements of EEDF and plasma parameters were conducted at powers ranging from 5 to 120 W and pressure of 0.3 mbar. The electronic density increases from 1.5×109 to 3.2×1010 cm-3 while the effective electron temperature decreases from 3.7 to 2.5 eV and then stabilizes beyond 70 W. They exhibit a transition between α and γ mode. The EEDFs were found to be Druyvesteyn-like below 70 W and then evolve to the Maxwellian beyond 70 W. OES method was applied to correlate with our Langmuir probe measurement. The intensities of the emission line at 7500 Å and 5145 Å follow the variation of ne with power density, and then show a transition regime at the same power as the previous case.