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Thermal Degradation of SiGe Interfaces Studied by X-Ray Reflectivity and Diffraction

Published online by Cambridge University Press:  22 February 2011

J. M. Hudson ,
A. R. Powell ,
D. K. Bowen ,
M. Wormington ,
B. K. Tanner ,
R. A. Kubiak  and
E.H.C. Parker
J. M. Hudson
Affiliation:
Dept. of Physics, University of Durham, Durham, DHl 3LE., U.K.
A. R. Powell
Affiliation:
Dept. of Engineering, University of Warwick, Cowntry, CV4 7AL., U.K.
D. K. Bowen
Affiliation:
Dept. of Engineering, University of Warwick, Cowntry, CV4 7AL., U.K.
M. Wormington
Affiliation:
Bede Scientific Software Division, Coventry, CV4 7EZ., U.K.
B. K. Tanner
Affiliation:
Dept. of Physics, University of Durham, Durham, DHl 3LE., U.K.
R. A. Kubiak
Affiliation:
Dept. of Physics, University of Warwick, Coventry, CV4 7AL., U.K.
E.H.C. Parker
Affiliation:
Dept. of Physics, University of Warwick, Coventry, CV4 7AL., U.K.
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Abstract

We demonstrate the use of x-ray diffraction to provide accurate compositional information, together with grazing incidence reflectivity to provide information on layer thicknesses and surface and interface roughnesses, on Si/Si1-xGex superlattice structures of less than 200nm total thickness.

The quality of SiGe interfaces has been investigated in superlattices where x varies from 0.1 to 0.5. At low Ge compositions the interfaces are shown to be smooth to a few angstroms. However, as the Ge composition in the SiGe layer approaches 50%, severe roughness is observed at the SiGe to Si interfaces, although the Si to SiGe interfaces remain relatively smooth.

Upon annealing for one hour at 850°C the Ge diffuses outwards from the SiGe layers and can be closely modelled by inclusion of a (2.4±0.3)nm linearly graded layer either side of the SiGe layer into a simulation program. The long range roughness at the SiGe to Si interface is lost upon annealing leaving only a short range roughness of similar size to the Si to SiGe interface roughness.

Reflectivity measurements have been shown to distinguish between interface roughness and interdiffusion for the annealed system.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 239: Symposium D – Thin Films: Stresses and Mechanical Properties III , 1991 , 455
Copyright
Copyright © Materials Research Society 1992

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References

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