Study of the Electron Density in an Inductively Coupled Plasma of Fluorine-Hydrogen-Argon Gas Mixture

In this paper, we present the results of non-contact measurements of electron density in an inductively coupled chemically active plasma at a pressure of 0.5 Torr. As a plasma-forming gas volatile compounds of halides BF3, SiF4, GeF4 mixed with hydrogen and argon were used. The electron density was determined by direct registration of the phase shift of the probing microwave radiation with a frequency of 58 GHz when passing through a cylindrical plasma layer. The method used makes it possible to increase the accuracy of measurements and level out the effects associated with the scattering and absorption of the useful signal by the plasma. It was experimentally shown that changing the content of argon and hydrogen in the ternary gas mixture (halogenide-hydrogen-argon) affects the electron density value in the discharge. Conclusions were drawn about the role of electron attachment to electronegative atoms and radicals as a mechanism for the loss of electrons in the studied low-pressure discharge in the presence of volatile fluorides.