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First-Principles Study of The Etching Reactions of HF and H2O with Si/SiO2 Surfaces

Published online by Cambridge University Press:  21 February 2011

Krishnan Raghavachari ,
G. S. Higashi ,
Y. J. Chabal  and
G. W. Trucks
Krishnan Raghavachari
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
G. S. Higashi
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
Y. J. Chabal
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
G. W. Trucks
Affiliation:
Lorentzian, Inc., 140 Washington Avenue, North Haven, CT 06473
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Abstract

First-principles quantum chemical techniques are used to unravel the mechanism leading to hydrogen-terminated silicon surfaces upon etching. Our calculations on model compounds indicate that kinetic rather than thermodynamic considerations are responsible for the H-passivation. In the etching reactions of HF, the initial oxide removal leads to Ftermination of the surface dangling bonds. Subsequent HF attack of the Si–Si back-bonds then leads to the final H-terminated surface. The principal driving force is the ionic nature of the Si–F bond which polarizes the Si–Si back-bonds. This polarization facilitates reactions with HF resulting in efficient removal of fluorine-bonded surface silicon as SiF4 leaving behind hydrogen. Analogous etching reactions of water involve larger barriers and can only be seen at elevated temperatures.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 315: Symposium Y – Surface Chemical Cleaning and Passivation for Semiconductor Processing , 1993 , 437
Copyright
Copyright © Materials Research Society 1993

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