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Surface Chemistry of Silicon and Germanium Treated with Hydrofluoric Acid Solutions: Slow Reactions of Process Residuals

Published online by Cambridge University Press:  25 February 2011

J. Yota  and
V.A. Burrows
J. Yota
Affiliation:
Arizona State University, Dept. of Chemical, Bio, and Materials Engineering and Center for Solid State Electronics Research, Tempe, AZ 85287-6006
V.A. Burrows
Affiliation:
Arizona State University, Dept. of Chemical, Bio, and Materials Engineering and Center for Solid State Electronics Research, Tempe, AZ 85287-6006
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Abstract

Solutions of hydrofluoric acid are used extensively in the processing of semiconductors, primarily in etching and in oxide stripping procedures. Such solutions are often buffered with ammonium fluoride to insure constant oxide stripping rates. Infrared spectroscopy of silicon and germanium surfaces treated with such solutions indicates that a thin film of ammonium salts will deposit on the materials unless they are immediately and very thoroughly rinsed following treatment. This thin film, comprised initially of ammonium bifluoride (NH4FHF), reacts with the semiconductor material to form ammonium fluoride (NH4F) as a reactive intermediate, and ammonium hexafluorometallate ((NH4)2 SiF6 or (NH4)2 GeF6). These reactions occur very slowly, over hours or days. They are apparently driven by favorable thermodynamics. This explanation is supported by the absence of comparable reactions using analogous chlorine-based solutions (HCI/NH4 CI). Aspects of the reaction mechanism for hexafluorometallate production is presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 204: Symposium E – Chemical Perspectives of Microelectronic Materials II , 1990 , 345
Copyright
Copyright © Materials Research Society 1991

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References

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