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CoSi and CoSi2 Phase Formation on Bulk and Soi Si Substrates

Published online by Cambridge University Press:  03 September 2012

S. L. Hsia ,
T. Y. Tan ,
P. L. Smith  and
G. E. Mcguire
S. L. Hsia
Affiliation:
Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708
T. Y. Tan
Affiliation:
Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708 MCNC, Center for Microelectronics, Research Triangle Park, NC 27709
P. L. Smith
Affiliation:
MCNC, Center for Microelectronics, Research Triangle Park, NC 27709
G. E. Mcguire
Affiliation:
MCNC, Center for Microelectronics, Research Triangle Park, NC 27709
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Abstract

We have studied the CoSi and CoSi2 phase formation sequence in (001) bulk and SOI Si wafers, using Co/Ti bimetallic layers as source materials which are suitable for growing epitaxial CoSi2 films on (001) Si. In bulk Si, co-formation of polycrystalline CoSi and epitaxial CoSi2 phases at T>500°C have been observed. These phases form respectively at the metal and Si sides of the film. For very long times and/or at high temperatures, only epitaxial CoSi2 is observed, e.g., for samples annealed at 560°C for 30 min or at 900°C for 10 s. When using (001) SOI Si with inexhaustible Co supply, only polycrystalline CoSi has been formed for a 900°C 10 s annealing, which is in contrast to the bulk Si results. This phenomenon is understood on the basis of Gibbs free energy reduction in forming the two phases. In the CoSi2 formation temperature range, Gibbs free energy release in forming CoSi2 is only ∼10% more than that of forming CoSi. Consequently, after all Si atoms have been consumed, the formation of CoSi becomes energetically more favorable, since the free energy reduction due to formation of 2x mole of CoSi is much larger than that due to formation of lx mole of CoSi2, where x is the SOI Si mole number.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 320: Symposium D – Silicides, Germanides, and Their Interfaces , 1993 , 373
Copyright
Copyright © Materials Research Society 1994

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