Energy-Loss Filtered Imaging of Segregation-Induced Interface Broadening in SiGe/Si p-Channel MOSFET Device Structures

SiGe/Si p-channel heteroepitaxial MOSFET test structures have been fabricated using solid-source molecular beam epitaxy. High-resolution transmission electron microscopy and energy-loss filtered imaging have been used to quantitatively determine the nanoscale Ge distributions across the SiGe alloy channel. The Ge profile at the edges of the alloy channel were found to be asymmetrical due to the effect of Ge segregation, with an exponential-like distribution directed toward the surface. The results agree well with the predictions of segregation theory and indicate that the concentration of Ge in the extended distribution lay in the range 10%-1% over a distance of several nanometers from the body of the channel. Secondary ion mass spectrometry measurements upon the same samples were insensitive to this short range extended Ge distribution.