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Time Resolved Diagnostics of RF Plasmas: a Fluid Model for ion Concentrations in the Sheath

Published online by Cambridge University Press:  21 February 2011

Richard A. Gottscho
Richard A. Gottscho*
Affiliation:
AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill, NJ 07074
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Abstract

A one-dimensional fluid model is presented for time-dependent ion concentrations in chlorine containing discharges. The ion formation rate is determined from experimental plasma-induced emission intensities. The local field is estimated from spectrally resolved laser-induced fluorescence data obtained in similar, BCl3 discharges. Quantitative agreement with experiment is obtained implying that the basic assumptions in the model are valid: (1) ground state ions in the sheath are formed predominantly by electron-impact ionization; (2) Cl2+ ion motion is mobilitylimited by charge exchange collisions with Cl2 neutrals; (3) the degree of Cl2 dissociation is ∼. 65% at a power density of 1.8 W cm−3; (4) the ion concentration near the electrode is spatially uniform throughout most of the rf cycle; and (5) there are two times during a low frequency rf cycle when ions experience a strong extraction force.

Semi-empirical models like the one described here should be useful in computational optimization of plasma processes such as etching and deposition, which are in wicre-spread use throughout the microelectronics industry.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 38: Symposium F – Plasma Synthesis and Etching of Electronic Materials , 1984 , 55
Copyright
Copyright © Materials Research Society 1985

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