In situ site-specific specimen preparation for atom probe tomography

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Atom probe tomography (APT) requires precisely prepared samples.
• Traditional methods can be time-consuming and destructive.
• Direct sample extraction from silicon wafers presents unique challenges.

Purpose of the Study:

• To develop rapid, site-specific sample preparation techniques for APT directly from silicon wafers.
• To investigate and mitigate gallium-induced damage during focused ion beam (FIB) sharpening.
• To enable high-quality APT analysis of nano-scale structures.

Main Methods:

• Systematic mounting of 12+ samples onto a microtip array.
• Site-specific annular mill extraction for targeted device removal.
• Focused ion beam (FIB) sharpening at 30 keV.
• Low-energy (5 keV and 2 keV) ion beam 'clean-up' for damage reduction.
• Atom probe tomography analysis.

Main Results:

• Sample preparation time reduced to approximately 2 hours.
• Gallium penetration depth at 30 keV is ~40 nm in {100} Si.
• Low-energy clean-up reduced damaged Si depth to ~5 nm (5 keV) and <1 nm (2 keV).
• Successful APT analysis of NiSi extracted from a Si wafer.

Conclusions:

• Rapid, site-specific sample preparation for APT from Si wafers is feasible.
• Low-energy ion beam cleaning effectively minimizes FIB-induced damage.
• Preservation of nano-structures allows for high-quality atom probe analysis.