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Surface Morphology of Si1−x−y GexCy Epitaxial Films Deposited by Low Temperature UHV-CVD

Published online by Cambridge University Press:  15 February 2011

S. John
Affiliation:
Microelectronics Research Center, Department of Electrical Engineering, University of Texas, Austin, TX 78712, [email protected].
E. J. Quinones
Affiliation:
Microelectronics Research Center, Department of Electrical Engineering, University of Texas, Austin, TX 78712, [email protected].
B. Ferguson
Affiliation:
Department of Chemical Engineering, University of Texas, Austin, TX 78712.
S. K. Ray
Affiliation:
On leave from IIT Kharagpur 721302, India.
C. B. Mullins
Affiliation:
Department of Chemical Engineering, University of Texas, Austin, TX 78712.
S. K. Banerjee
Affiliation:
Microelectronics Research Center, Department of Electrical Engineering, University of Texas, Austin, TX 78712, [email protected].
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Abstract

Si1−x−y GexCy epitaxial films offer wider control of strain and bandgap. In such films the morphology is an important indication of the crystalline quality of the material. We report on the morphology of Si1−x−y GexCy epitaxial thin films deposited by Ultra High Vacuum Chemical Vapor Deposition at a temperature of 550° C and deposition pressures ranging from 1 to 10 mTorr. The precursors used were Si2H6, GeH4 and CH3SiH3. Germanium mole fractions ranging from 0% to 40% were studied with carbon concentrations varying from 2×1019 to 2×1021 atoms/cm3. AFM analysis of the surface indicates that the roughness is a function of both the carbon concentration and the film thickness. For high germanium concentrations with thickness beyond the critical thickness (of Si1−xGex), carbon is found to decrease the surface roughness of the film. Thus the surface morphology confirms the strain compensation provided by carbon which is also observed using XRD. For films below the critical thickness, as the carbon concentration is increased, three dimensional islanding is observed by RHEED and AFM, degrading the epitaxial quality of the material.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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