Absolute density and reaction kinetics of fluorine atoms in high-density c-C4F8 plasmas

Absolute density and reaction kinetics of fluorine (F) atoms in high-density octafluorocyclobutane (c-C4F8) plasmas were examined using vacuum ultraviolet absorption spectroscopy. The F atom densities, corresponding to electron densities ranging from 1x10(11) to 5x10(12) cm(-3), were 1 x 10(12)-5 x 10(13) cm(-3) for gas pressures of 2-7 mTorr and rf powers of 0.2-1.5 kW. The F atom density was linearly dependent on the electron density for n(e),<1.5x10(12) cm(-3). According to lifetime measurements in the afterglow, two decay processes were found in the F atom density: exponential (first-order kinetics) and Linear (zero-order kinetics) decay components. The linear-decay component became significant at high gas pressures. The time constant,of the exponential-decay component ranged from 5 to 100 ms, which corresponds to surface loss probabilities of 10(-1)-10(-3). The surface loss probability varied inversely with the F atom density. (C) 1998 American Institute of Physics.