Kinetics of F atoms and fluorocarbon radicals studied by threshold ionization mass spectrometry in a microwave CF4 plasma

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Abstract
The absolute concentration of fluorine atoms (F), a parameter of great importance for the characterization and modeling of etching plasmas, was measured by means of threshold ionization mass spectrometry in a CF4 microwave plasma (p=15–100 mTorr). The kinetics of these atoms and those of CF2 and CF3 radicals were studied by pulsing the plasma and time-resolved detection of these radicals with mass spectrometer. Sticking coefficients of F atoms on the different surrounding surfaces were estimated, as a function of the discharge parameters and the nature of the surfaces interacting with the plasma. It was found that the sticking of F atoms on hexatriacontane polymer surface is highly activated by the plasma generated ions and/or ultraviolet radiations.