Diagnoses of inductively coupled SF6 and N2 plasmas at atmospheric pressure

Radio-frequency inductively coupled SF6 and N-2 plasmas vr ere generated at atmospheric pressure, as mixed-gas plasma in argon. Total flow rate was kept constant at 225 slpm through the sheath channel of an 82 mm inner diameter torch for different ratios of argon and the concerned gas. Furthermore, a two-dimensional and optically thin ICP model was solved numerically with the same operating conditions. Both the experimental and theoretical results revealed that Ar ICP contracted drastically with inclusion of SF6 and moderately with N-2; a flow rate of 15 slpm for SF6 was the maximum limit for stable plasma whereas the maximum Bow rate for N-2 was 65 slpm. The electron density, measured by the Stark broadening method, was decreased by SF6 gas inclusion, at a low Bow rate (5 slpm), due to electronegativity or electron absorption behavior of the gas. However, the density was slightly higher at a Bow rate of 10 slpm for SF6 compared to a 5 slpm flow ratel because of high rate ionization of S atoms due to its lower ionization potential compared to Ar. The electron density was decreased slightly by N-2 inclusion due to the presence of the diatomic N-2 particle and due to similar order ionization of N atoms compared to Ar atoms. (C) 1999 Elsevier Science S.A. All rights reserved.