Detection of Ge and Si Intermixing in Ge/Si Using Multiwavelength Micro-Raman Spectroscopy
In this study, we report the detection of Ge and Si intermixing in epitaxially grown Ge/Si after successive thermal anneals using multiwavelength Raman spectroscopy. We have studied dependence of Ge and Si intermixing on annealing temperature and Raman on excitation wavelength. Very strong excitation wavelength and film structure dependence of signal-to-noise (S/N) ratio of measurements was observed. Suitable excitation wavelengths must be chosen to properly detect and characterize Si and Ge intermixing, based on the stacking order of epitaxial films and thicknesses.
Figure 1 shows 514.5nm excited Raman spectra from reference Si, reference Ge and epitaxially grown Ge/Si wafers before and after thermal annealing. As grown Ge/Si wafers showed very distinct Ge and Si Raman peaks. Si and Ge intermixing was found in one annealing condition. Ge epitaxial was converted to Si1-xGexafter annealing.