Inelastic electron scattering observation using energy filtered transmission electron microscopy for silicon --...

Area of Science:

• Materials Science
• Nanotechnology
• Electron Microscopy

Background:

• Accurate characterization of Germanium distribution in Si-SiGe nanostructures is crucial for semiconductor device performance.
• Conventional imaging techniques like STEM Z-contrast can be affected by diffraction and sample orientation.

Purpose of the Study:

• To develop and validate a novel EFTEM-based technique for imaging Germanium distribution in Si-SiGe nanostructures.
• To compare the proposed technique with existing methods like STEM Z-contrast.

Main Methods:

• Utilizing energy filtered transmission electron microscopy (EFTEM) for inelastic electron scattering contrast imaging.
• Acquiring and analyzing electron energy loss spectra (EELS) in the 50-100 eV range to identify Ge-sensitive spectral features.
• Generating Germanium maps by calculating the ratio of EFTEM images acquired at 90 eV and 60 eV, reflecting EELS background slope variations.

Main Results:

• A specific spectral region (50-100 eV) in EELS was identified as highly sensitive to Germanium concentration.
• The EFTEM ratio imaging technique effectively maps Germanium distribution with high contrast.
• The developed method eliminates elastic scattering artifacts and is insensitive to sample thickness and grain orientation.

Conclusions:

• The proposed EFTEM technique provides a robust and advantageous alternative for Germanium mapping in Si-SiGe nanostructures.
• This method enables accurate observation and quantification of Ge concentration depth profiles in buried SiGe layers.