Spectroscopic techniques for characterization of high-mobility strained-Si CMOS

The application of Raman spectroscopy and spectroscopic ellipsometry (SE) for characterization of strained silicon layers on SiGe virtual substrates is demonstrated. X-ray diffraction measurements (XRD) for calibration of Raman results have been carried out on strained Si/SiGe structures. For the composition-dependent shift of the Si-Si vibration in SiGe the relation ωSi-Si=520.6-68xGe is found, the strain shift coefficient for the longitudinal optical phonon in Si is estimated as −750 cm−1. Three different samples with strained-Si layers on step-graded SiGe profiles with nominal final Ge concentrations in the range from 10% to 24% were investigated by XRD, transmission electron microscopy, Raman spectroscopy and SE to determinate the parameters Si cap thickness, strain in the Si layer, Ge content and relaxation of the SiGe film. A good correspondance of the results from all techniques is found.