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

Abstract

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 1 × 1011 to 5 × 1012 cm-3, were 1 × 1012-5 × 1013 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 ne<1.5×1012 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. © 1998 American Institute of Physics.