Recombination coefficients for Cl on plasma- conditioned yttrium oxide chamber wall surfaces

摘要

Studies of power-modulated chlorine inductively coupled plasmas (ICPs) bounded by yttria-coated chamber walls are presented. Time-resolved optical emissions from Cl and Xe actinometry trace gas were recorded over the 740-920 nm region as power at 13.56 MHz was modulated between high power and no power. The intensity ratio of Cl-to-Xe emission, proportional to Cl number density, n(Cl), followed the modulation in power, allowing Cl heterogeneous loss coefficients, gamma(Cl), to be obtained from a simple time-resolved, 0-dimensional model of the afterglow period that best matched computed relative changes in n(Cl) at the beginning and end of the powered period, with gamma(Cl) as the only adjustable parameter. This approach only requires a treatment of diffusion and avoids complications introduced by attempting simulations of the full modulation period. Cl recombination coefficients were determined on the mostly yttria surfaces for Cl-2 ICPs (a) immediately after NF3 plasma cleaning (gamma(Cl) = 0.20) (b) during long exposure to the Cl-2 plasma with no substrate bias (gamma(Cl) = 0.11), and (c) during Si etching with substrate bias (gamma(Cl) = 0.055-0.070). For Cl-2/5% O-2 ICPs, these values are 0.28, 0.17, and 0.030, respectively. These results compare favorably to qualitative behavior reported previously for continuous Cl (2) and Cl-2/O-2 ICPs in this yttria-coated chamber. Published under license by AIP Publishing.