AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA6
Time-Resolved Measurements of Fluorocarbon Radical Concentrations during Pulsed Oxide Etching Plasmas

Tuesday, October 3, 2000, 3:40 pm, Room 311

Session: Plasma Diagnostics I
Presenter: T.M. Bauer, University of New Mexico
Authors: T.M. Bauer, University of New Mexico
X. Wu, University of New Mexico
J.L. Cecchi, University of New Mexico
Correspondent: Click to Email
We have measured the time evolution of the concentrations of the fluorocarbon radical precursors, CF@sub 2@ and CF, in pulsed plasmas using oxide etching chemistries. These measurements were performed in an inductively coupled plasma (ICP) reactor with a CHF3/Ar feedstock. We have explored a range of ICP powers of 300 to 900 W and a range of total pressure from 10 to 30 mTorr. The concentrations of CF@sub 2@ and CF, were measured with a wavelength-modulated diode laser spectroscopy system, modified to provide data with a time resolution of less than 0.3 ms. The pulse repetition rate and duty factor were varied to explore the full range of CF@sub 2@ CF and kinetics. Following the initiation of the plasma, [CF] increases in a nearly first-order manner. The behavior of [CF@sub 2@] is more complicated. Under pulsing conditions where [CF@sub 2@] remains nonzero for the entire period, there is an initial, very rapid (< 3 ms) decrease in [CF@sub 2@], indicating an enhanced loss, followed by a slower rise to equilibrium. After the termination of the plasma, [CF@sub 2@] shows a rapid increase, followed by an exponential decay. [CF] shows only an exponential decrease. The time constant for [CF@sub 2@] decay is in the range of 0.08-0.20 s, while the time constants for [CF] are more than a factor of ten smaller. Both time constants decrease with increasing pressure, and show a much smaller dependence on ICP power. We interpret our measurements with simple kinetic models and have extracted kinetic parameters during both the plasma pulse and after plasma termination.