DECOMPOSITION OF GASEOUS DIELECTRICS (CF4, SF6) BY A NONEQUILIBRIUM PLASMA - MECHANISMS, KINETICS, MASS-SPECTROMETRIC STUDIES AND INTERACTIONS WITH POLYMERIC TARGETS

Fluorinated monomers such as sulfur hexafluoride SF6 and carbon tetrafluoride CF4 are widely used, at low ps pressures in plasma etching of silicon and insulating substates for microelectronic applications, and at high pressures in high voltage insulation systems. This paper reports on the decomposition of SF6, CF4 and their mixtures by a non-equilibrium plasma and their interaction with polyethylene films. The presence of oxygen and water vapor as trace contaminants and their role in the decomposition mechanisms were pointed out both by mass spectrometry and optical emission spectroscopy. The comparison of the results obtained by kinetic calculations and those measured by and plasma diagnostic techniques brought evidence on the participation of the fluorine atoms in the heterogeneous mechanisms. Finally, the effect of the addition of a fluorine containing molecule such as CF4 to SF6 discharges on the energetic aspect of the discharge, the decomposition mechanisms and the fluorination processes will be discussed. The excitation efficiency of the electrons was correlated to the fluorine concentration as measured by actinometry and to surface fluorination as shown by the XPS analysis.