Measurements of neutral and ion composition, neutral temperature, and electron energy distribution function in a CF4 inductively coupled plasma

In this article, we present comprehensive measurements of the neutral numbe r densities, ion number densities, and the electron energy distribution fun ction in a CF4 inductively coupled plasma at pressures between 1 and 30 mTo rr, and deposited powers between 150 and 550 W. High degrees of dissociatio n are observed at the lower pressures. We believe this is a result of the l arge electron temperature at the lower pressures. The measurements of all t he dominant radical and stable neutral species using appearance potential m ass spectrometry allows the estimation of the neutral temperature at the ne utral 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 930 K are measured at t he sampling aperture. The increase in neutral temperature with power at a c onstant pressure results in a decrease in the total neutral number density at a constant pressure. The electron temperature is sensitive to the neutra l number density, especially at low densities. This leads to a significant increase in the electron temperature with power, resulting in the higher de grees of dissociation observed at low pressures. The number densities of ra dicals and their corresponding ions are generally strongly correlated in th e plasma. We show indirect evidence for large surface loss coefficients for C and CF radicals. (C) 2001 American Vacuum Society.