Observation of the forbidden doublet optical phonon in Raman spectra of strained Si for stress analysis

Using high numerical aperture lenses, we detected doublet optical phonon, forbidden by selection rules, in Raman spectra of Si strained in the (001) plane (bulk Si as well as strained Si device structure grown on SiGe). This allowed us to quantitatively determine stress and its distribution in strained Si with the similar to 10% accuracy, assuming symmetric biaxial stress. At the same time, we demonstrate some deviations of the real stress from the assumed model. For better accuracy, one has to consider these deviations as well as a possibility of improvement of available Si phonon deformation potential values. (C) 2010 American Institute of Physics. [doi:10.1063/1.3474604]