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Thermal Strain Measurements in Epitaxial CoSi2/Si by Double Crystal X-Ray Diffraction

Published online by Cambridge University Press:  22 February 2011

Gang Bai ,
Marc-A. Nicolet ,
Thad Vreeland Jr. ,
Q. Ye ,
Y. C. Kao  and
K. L. Wang
Gang Bai
Affiliation:
California Institute of Technology, Pasadena, CA 91125
Marc-A. Nicolet
Affiliation:
California Institute of Technology, Pasadena, CA 91125
Thad Vreeland Jr.
Affiliation:
California Institute of Technology, Pasadena, CA 91125
Q. Ye
Affiliation:
UCLA, Los Angeles, CA 90024
Y. C. Kao
Affiliation:
UCLA, Los Angeles, CA 90024
K. L. Wang
Affiliation:
UCLA, Los Angeles, CA 90024
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Abstract

The perpendicular x-ray strain of epitaxial CoSi2 films grown on Si(111) substrates at ∼ 600°C by MBE was measured at various temperatures. Within experimental error margins, the strain decreases linearly with rising temperature at a rate of (1.3±0.1) × 10-5/°C from room temperature up to 600°C. Over that temperature range and the duration of a complete measurement (∼5h to ∼ 2h), these strain values remain reversible. At 593°C, the x-ray strain is -0.85%, which is about the strain that a stress-free CoSi2 film on Si(111) would have at that temperature. This results show that the stress in the epitaxial CoSi2 film is fully relaxed at the growth temperature. Strains below the growth temperature are induced in the film by the difference in the linear coefficient of thermal expansion of CoSi2 and Si. They were calculated by assuming that the density of misfit dislocations formed at the growth temperature remains constant. The slope of the strain-temperature dependence obtained that way agrees with the measured slope if the unknown Possion ratio of CoSi2 is assumed to be VcoSi2 = 0.35. A film stress of ∼ 0.8 GPa at room temperature was calculated using the above value for the Possion ratio, 130 GPa for the Young modulus, and the measured x-ray strain.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 130: Symposium C – Thin Films: Stresses and Mechanical Properties I , 1988 , 35
Copyright
Copyright © Materials Research Society 1989

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References

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