Multiwavelength ellipsometry at strained Si 1-x Ge x layers on Si substrate

Abstract

Rapid characterization of thin epitaxial Si<SUB>1-x</SUB>Ge<SUB>x</SUB> layers on silicon substrate was made by multi-wavelength ellipsometry. Si<SUB>1-x</SUB>Ge layers were deposited by chemical vapor deposition in an atmospheric pressure reactor at 700 degree(s)C. A thickness variation of these strained thin layers (20 to 80 nm) was generated for different germanium contents in the range of 0.10 < X < 0.22. For ellipsometrical measurements a PLASMOS-ellipsometer SD 2000 at an incident angle of 70 degree(s) at different wavelengths was used. Theoretical simulations for measured ellipsometrical angles (Psi) and (Delta) and an iteration procedure were achieved to estimate the refractive index and thickness of Si<SUB>1-x</SUB>Ge<SUB>x</SUB> layers on silicon substrate. The compositions are obtained by x-ray double crystal diffractometry to provide a correlation to ellipsometrical measurements. Stress in the thin layers is determined by Raman line shift. We found a relation between the real part of the refractive index of Si<SUB>1-x</SUB>Ge<SUB>x</SUB> layers and the Ge-content in these layers at the wavelengths of 632.8 nm and 785 nm.