DETERMINATION OF THICKNESS AND GE CONTENT OF STRAINED SI1-XGEX LAYERSON SI SUBSTRATE BY 2-WAVELENGTH ELLIPSOMETRY

Fixed-wavelength ellipsometry at two wavelengths, lambda = 632.8 and 7 85 nm, is used for the determination of thickness and composition of t hin epitaxial Si1-xGex films on silicon substrates. The results are co mpared to those obtained by X-ray double crystal diffractometry (DCD). The real part of the refractive index at 785 nm of these strained thi n Si1-xGex layers is determined for the Ge content range of 0.10 < x < 0.22. A linear dependence of the real part of the refractive index on the Ge content is found. For fitting experimental and calculated curv es it is necessary to adjust the thickness of a native oxide on top of the Si1-xGex layer. To obtain the best agreement in thickness measure ments from both techniques, ellipsometry and DCD, it is necessary to m odify the imaginary part of the refractive index.