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Kinetic Analysis of Chlorofluorocarbon Discharges

Published online by Cambridge University Press:  21 February 2011

Herbert H. Sawin ,
Akimichi Yokozeki ,
Aaron J. Owens  and
Kenneth D. Allen
Herbert H. Sawin
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
Akimichi Yokozeki
Affiliation:
Freoen® Products Laboratory
Aaron J. Owens
Affiliation:
Engineering Department, E.I. du Pont de Nemours and Company, Wilmington, DE 19898
Kenneth D. Allen
Affiliation:
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
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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.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 38: Symposium F – Plasma Synthesis and Etching of Electronic Materials , 1984 , 235
Copyright
Copyright © Materials Research Society 1985

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