The role of negative ions in the formation of particles in low‐pressure plasmas
作者:
Seung J. Choi,
Mark J. Kushner,
期刊:
Journal of Applied Physics
(AIP Available online 1993)
卷期:
Volume 74,
issue 2
页码: 853-861
ISSN:0021-8979
年代: 1993
DOI:10.1063/1.354877
出版商: AIP
数据来源: AIP
摘要:
Large particles (tens of nm to tens of &mgr;m in diameter) are problematic in low‐pressure (<1 Torr) plasma processing (etching, deposition) discharges because they can contaminate the product and can perturb electron transport. Although the source of these particles has been studied by a number of groups, a definitive explanation is still lacking. In this paper, we theoretically investigate the role of negative ions in the formation of large clusters, the precursors to particles, in low‐pressure plasmas. We find that the formation of particles requires a critically large cluster. Forming the critically large cluster requires longer residence times in the plasma than is usually possible if clustering involves only neutral particles. We propose that negatively charged intermediates, which are trapped in electropositive plasmas, increase the average residence time of clusters to allow the growth of critically large clusters.
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