Kinetics of CFX (x=1 –3) Radicals and Electrons in RF CF4-H2, CHF3-H2 and CHF3-O2 Plasmas

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Abstract
The densities of CF, CF2, and CF3 radicals have been measured in RF CF4-H2, CHF3-H2 and CHF3-O2 plasmas using infrared diode laser absorption spectroscopy. In H2 additive fluorocarbon plasmas, it was found that fluorocarbon film formation on the electrodes increases the radical densities in the plasma by reducing the surface loss probability and producing the radicals through sputtering of the fluorocarbon film. In CHF3-O2 plasma, the CF radical density decreased rapidly when a small amount of O2 gas was added due to the removal of fluorocarbon film, whereas an increase in the density of CF3 was observed. The spatially averaged electron density has also been measured using a microwave interferometer together with the Ar* emission intensity under the same conditions as the radical measurements. The variations in the electron temperature and density are explained qualitatively by the change in the electron loss process in the gas phase induced by H2 or O2 admixture.