Kinetics of fluorine atoms in high-density carbon–tetrafluoride plasmas

Reaction processes of fluorine ~F! atoms in high-density carbon–tetrafluoride (CF4) plasmas were investigated using vacuum ultraviolet absorption spectroscopy. A scaling law nF}(nenCF4) 0.5– 0.7 was found experimentally, where nF is the F atom density and ne and nCF4 stand for the electron and parent gas (CF4) densities, respectively. The lifetime measurement in the afterglow showed that the decay curve of the F atom density was composed of two components: a rapid decay in the initial afterglow and an exponential decrease in the late afterglow. The decay time constant in the initial afterglow t1 satisfied the scaling law t1}(nenCF4) 2(0.3– , which is a consistent relationship with the scaling law for the F atom density. The two scaling laws and the lifetimes of CFx radicals suggest that the major loss process of F atoms in the initial afterglow is the reaction with CFx radicals ~probably, x53! on the wall surface. The loss process in the late afterglow was simple diffusion to the wall surface. The surface loss probability of F atoms on the chamber wall was evaluated from the decay time constant in the late afterglow, and was on the order of 10. © 1997 American Institute of Physics. @S0021-8979~97!02824-7#