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

Paper PS2-TuA2
Comprehensive Measurements of Neutral and Ion Number Densities, Neutral Temperature, and EEDF in a CF@sub 4@ ICP

Tuesday, October 3, 2000, 2:20 pm, Room 311

Session: Plasma Diagnostics I
Presenter: H. Singh, University of California at Berkeley
Authors: H. Singh, University of California at Berkeley
J.W. Coburn, University of California at Berkeley
D.B. Graves, University of California at Berkeley
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We present comprehensive measurements of the neutral number densities, ion number densities, neutral temperature, and the electron energy distribution function in a CF4 inductively coupled plasma at pressures between 1 and 30 mTorr, and deposited powers between 150 and 550 W. High degrees of dissociation are observed at the lower pressures. We believe this is a result of the large electron temperature (5-9 eV) at the lower pressures. The measurements of all the dominant radical and stable neutral species using appearance potential mass spectrometry allows the estimation of the neutral temperature at the neutral sampling aperture. The neutral temperature is also estimated from the change in the number density of a trace amount of argon added to CF4 when the plasma is turned on. Neutral temperatures up to 925 K are measured at the sampling aperture. The increase in neutral temperature with power at a constant pressure results in a decrease in the total neutral number density at a constant pressure. The electron temperature is sensitive to the neutral number density, especially at low densities. This leads to a significant increase in the electron temperature with power, resulting in the higher degrees of dissociation observed at low pressures. The number densities of radicals and their corresponding ions are generally strongly correlated in the plasma. We show evidence for a large surface loss coefficients for C and CF radicals.