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Kinetic Analysis of Chlorofluorocarbon Discharges
Published online by Cambridge University Press: 21 February 2011
Abstract
The fundamental plasma kinetics of chlorofluorocarbon discharges have been studied experimentally and modeled. Electrical impedance analysis of the plasma discharge during the etching process was used to estimate the average electron energy and the electron concentration. Assuming the electron-impact generation of reactant species is the rate limiting step, the etching rate of polysilicon etching was modeled using a simplified expression for the electron-impact rate coefficient for dissociation and the experimentally estimated electron densities and electron energies. Dissociative electron attachment should play a significant role in the production of etchant species at low electron energies. The lower threshold energy and the larger cross-section (σ) for dissociative attachment of chlorofluorocarbons (σmax,∼6×10-18 cm2 at ∼ 3 eV for CF3Cl) in coomprpsanrtison to that of fluorocarbons (σmax ∼0.8×10-18 cm2 at ∼7 eV for CF4 ), increases the significance of this machanism in chlorofluorocarbon discharges. In addition, the production of appreciable concentrations of C1- could influence the transport of positive ions to the electrode surfaces.
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- Copyright © Materials Research Society 1985
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