Two-dimensional quantitative mapping of arsenic in nanometer-scale silicon devices using STEM EELS-EDX spectroscopy

Area of Science:

• Materials Science
• Semiconductor Physics
• Analytical Chemistry

Background:

• Accurate characterization of dopant distribution is crucial for silicon semiconductor device performance.
• Nanometer-scale dopant detection requires advanced microscopy techniques.
• Arsenic is a critical n-type dopant in advanced semiconductor fabrication.

Purpose of the Study:

• To evaluate field emission gun nanoprobe scanning electron transmission microscopy (STEM) techniques for detecting arsenic in silicon devices.
• To optimize experimental procedures for enhanced signal-to-noise ratio and sensitivity.
• To compare STEM-based dopant analysis with secondary ion mass spectrometry (SIMS).

Main Methods:

• Utilizing field emission gun nanoprobe scanning electron transmission microscopy (FEG-STEM).
• Employing energy dispersive X-ray (EDX) and electron energy loss spectroscopy (EELS) for elemental analysis.
• Quantifying spectrum profiles and comparing with SIMS data.

Main Results:

• Arsenic detection below 0.1% is achievable with optimized STEM EDX and EELS.
• STEM EDX/EELS results show good agreement with SIMS analyses.
• Variable interface segregation of arsenic was observed in epitaxial devices.
• STEM EDX mapping revealed significant heterogeneities and segregation in BiCMOS transistor emitters.

Conclusions:

• FEG nanoprobe STEM-EDX/EELS is a powerful tool for nanometer-scale arsenic dopant analysis in silicon.
• The technique provides high sensitivity and can identify dopant segregation phenomena.
• Results are comparable to SIMS, offering complementary spatial information.