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Ion velocity distributions in helicon wave plasmas: Magnetic field and pressure effects

Nakano, T. and Giapis, K. P. and Gottscho, R. A. and Lee, T. C. and Sadeghi, N. (1993) Ion velocity distributions in helicon wave plasmas: Magnetic field and pressure effects. Journal of Vacuum Science and Technology B, 11 (6). pp. 2046-2056. ISSN 1071-1023. http://resolver.caltech.edu/CaltechAUTHORS:NAKjvstb93

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Abstract

Consideration of ion transport in high density, low pressure plasma systems is important for meeting process requirements in the manufacturing of ultra-large-scale integrated circuits. The ion energy and angular distributions at the boundary between the plasma and the wafer, the sheath, influence etching selectivity, linewidth control, plasma-induced damage, and microscopic etching uniformity. These distributions, in turn, are easily altered by changing the magnetic field profile and/or the neutral gas pressure. Using Doppler-shifted laser-induced fluorescence, metastable ion velocity distribution functions in helicon-wave-excited Ar plasmas are measured. Two magnetic field configurations are examined. For a magnetic "mirror," where the field exhibits a maximum and a saddle point in the source, the plasma is observed to be asymmetric and nonuniform: this leads to broadened velocity distributions and significant ion drift from one region of the plasma to another. As the pressure is increased in the mirror field configuration, the transverse ion "temperature" exhibits a maximum as a function of pressure and, when etching is ion-flux limited, either decreasing or increasing the pressure should result in improved linewidth control. The plasma is more symmetric when the magnetic field is reversed in the source and again downstream. With this double cusp configuration, the transverse ion temperature decreases monotonically with pressure, and improved linewidth control in the ion-flux limit would be obtained by operating at higher pressure.


Item Type:Article
Additional Information:© 1993 American Vacuum Society (Received 3 June 1993; accepted 25 September 1993)
Subject Keywords:HELICON WAVES; ARGON IONS; DENSE PLASMA; VELOCITY DISTRIBUTION; ION TEMPERATURE; PRESSURE DEPENDENCE; MAGNETIC MIRROR CONFIGURATIONS; CUSPED GEOMETRIES; FLUORESCENCE
Record Number:CaltechAUTHORS:NAKjvstb93
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:NAKjvstb93
Alternative URL:http://dx.doi.org/10.1116/1.586541
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5293
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:09 Oct 2006
Last Modified:26 Dec 2012 09:04

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