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-d ensity octafluorocyclobutane (c-C4F8) plasmas were examined using vacu um ultraviolet absorption spectroscopy. The F atom densities, correspo nding 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 r f powers of 0.2-1.5 kW. The F atom density was linearly dependent on t he 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-or der kinetics) decay components. The linear-decay component became sign ificant at high gas pressures. The time constant,of the exponential-de cay component ranged from 5 to 100 ms, which corresponds to surface lo ss probabilities of 10(-1)-10(-3). The surface loss probability varied inversely with the F atom density. (C) 1998 American Institute of Phy sics.