Practical Considerations in Atom Probe Tip Making Using FIB-SEM - - PowerPoint PPT Presentation

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Practical Considerations in Atom Probe Tip Making Using FIB-SEM - - PowerPoint PPT Presentation

May 31, 2023 32 likes •192 views

Practical Considerations in Atom Probe Tip Making Using FIB-SEM Nicholas Antoniou & Andrew Magyar Center for Nanoscale Systems Harvard University Outline The 3D Atom Probe Microscope Operation of the 3D Atom Probe Sample

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SLIDE 1

Practical Considerations in Atom Probe Tip Making Using FIB-SEM

Nicholas Antoniou & Andrew Magyar Center for Nanoscale Systems Harvard University

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SLIDE 2

Outline

  • The 3D Atom Probe Microscope
  • Operation of the 3D Atom Probe
  • Sample requirements
  • Prep Process
  • Tricks and treats in making tips
  • Examples
  • Conclusion

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SLIDE 3

The 3D Atom Probe

  • 3D location of the atoms in a sample plus chemical

identification; datasets of 106 – 108 atoms

  • Lateral resolution ~ 0.5 nm, depth resolution ~0.2 nm
  • Works with metals (HV mode) and sub-3 eV bandgap

semiconductors (Laser mode)

  • In principle, complete chemical identification from entire

periodic table

  • Prerequisites for sample analysis: rough estimate of

composition, conductivity, mechanical stability, and region of interest; sample must be free of cracks and vacuum stable

  • Prerequisite instruments for sample prep: SEM, FIB with lift-
  • ut capability, possibly electro-polishing (for metals)
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SLIDE 4

The Tip is the Sample

  • Ideal Tip
  • 100-80 nm diameter
  • Taper is material dependent. Thermal conductivity is an
  • issue. A cylinder of 1-2 um tall 100-80 nm diameter

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SLIDE 5

The 3D Atom Probe

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SLIDE 6

Multi-component Samples

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SLIDE 7

The 3D Atom Probe Technique Dataset

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Si Ga

100 200 100 1000 10000

Counts Mass-to-Charge Ratio (Daltons) uncorrected

Milled at 30keV throughout, Ga implantation not useful

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SLIDE 8

Bar Shape, Attach and Cap Material

  • Right Angle Wedge vs Equilateral Wedge

– Prefer Right angle because of fewer interfaces in the sharpening reducing risk of fracture

  • W stronger attach bond but less desirable for cap
  • Pt weaker attach but more desirable for cap
  • Carbon is not used for either
  • Low acceleration clean up but at 10keV

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TOP

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SLIDE 9

Sample Preparation

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Volume of interest

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SLIDE 10

Right Angle Wedge Prep

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SLIDE 11

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Sample Preparation

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SLIDE 12

Making a Pyramid

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SLIDE 13

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Sample Preparation

Final Annular Milling at ~ 45pA 10 keV FIB

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SLIDE 14

Tip Made Out of Nanowire

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  • Nanowire mounted on flat top

SiO2 cladded Si, with deposited Ni protective layer

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SLIDE 15

Silicon hyperdoped with Au

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SiAu 6e15 implant Pulsed-Laser Melted with YAG 355

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SLIDE 16

Conclusion

  • The 3D Atom Probe is a very powerful analysis

tool that provides 3D location of the atoms in a sample plus chemical identification

  • The sample prep requirements are demanding
  • FIB-SEM is very well suited to prepare samples

especially site specific ones

  • Correlating TEM to 3D Atom Probe improves

results

  • Acknoledgements:
  • Dr. A. Akey, Dr. M. Baram, and Peter Felfer
  • http://www.youtube.com/watch?v=NcG9H3v3xW4

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