Photoreflectance Study Of Strain At Si/SiO2 Interfaces Prepared By Thermal Oxidation Of Silicon

We have used the contactless electromodulation technique of photoreflectance (PR) to investigate the strain in the near surface region (-100 R) of Si in thermally prepared (~100A) Si/Si02 interfaces. We have tracked the position of the E1 optical feature (Λ3 - Λl transitions) relative to its position in a reference Si wafer (not intentionally oxided). From the observed red-shifts we can deduce both the magnitude and sign (tensile) of the strain. These observations are consistent with the compressive stress in the SiO, at the Si/Si02 interface as evaluated previously using it transmission, ellipsometry and laser-beam deflection studies.