Nanoscale Secondary Ion Mass Spectrometry (Nano SIMS)

Imaging impurities in a Silicon Carbide MOSFET cross section. Phosphorous identified in the n-source and PSG; Aluminum found in p-well; and Boron found in the poly-Si electrode. The results of this NanoSIMS measurement were consistent with results of SCM and DPC-STEM analysis (not shown)

Nanoscale secondary ion mass spectrometry (Nano SIMS) is a highly sensitive chemical analysis technique used to acquire 2D and 3D maps of elemental distribution information with exceptionally high spatial and mass resolutions. It is typically used to produce images of elemental concentration.

Covalent partners with Toray Research Center to offer Nano SIMS on one of only about 50 total instruments for this technique available around the world.

Strengths

1D (line-scan), 2D and 3D element maps can be collected
High mass resolution for isotope analysis
Elemental sensitivity much better than EDS or XPS for trace element analysis

Limitations

Relatively low depth resolution (10-15 nm) compared to other SIMS methods due to the higher primary ion accelerating energy in NanoSIMS
Quantitative analysis requires reference sample(s) to be prepared

Technical Specifications:
Example Outputs Instruments Used Sample Requirements

Learn More:
How Nano SIMS Works Additional Resources Related Techniques

Example Outputs

Imaging impurities in a Silicon Carbide MOSFET cross section. Phosphorous identified in the n-source and PSG; Aluminum found in p-well; and Boron found in the poly-Si electrode. The results of this NanoSIMS measurement were consistent with results of SCM and DPC-STEM analysis (not shown).

From: Toray Research Center

Instruments Used for Nano SIMS

CAMECA NanoSIMS 50L

Sensitivity: ppm to 1 at.% depending on element
Depth Range: from several 10’s of nm to ~100 microns
Depth Resolution: 10-15 nm
Elements Detected: H – U
Primary Ion: O- or Cs+
Beam Diameter: 50 nm
Mass Analyzer: Magnetic Sector
Number of detected ions in multicollection: 7, analyzed simultaneously

Sample Requirements

Solid phase
Vacuum stable
Sample size limitations:
- 5-10 nm square analytical area
- Sample size 1 by 1 mm to 25 by 25 mm (needs to be verified by TRC)
- Maximum sample thickness: 3.5 mm or less
- Small chips can be analyzed by mounting on a dummy wafer
- Large wafers must be cut to size before analysis

How Nano SIMS Works

Nanoscale secondary ion mass spectrometry (NanoSIMS) uses an applied beam of high-energy sputtering ions or neutral atoms to ablate secondary-ion fragments from a sample surface. The secondary species are then collected and parsed according to their mass-charge ratio to produce a mass spectrum that can be analyzed to identify the elements and molecular fragments present in the sample surface. The technique has good elemental sensitivity and mass resolution that can be used for trace element detection and isotope analysis.

NanoSIMS is unique from other mass spectrometry techniques for its particularly high spatial resolution, achieved using a specialized ion beam source setup and a magnetic-sector mass analyzer that can perform multicollection. The ion source in a NanoSIMS instrument is positioned perfectly perpendicular and very near to the sample surface with a coaxial lens assembly that simultaneously extracts the ablated secondary ions as they are sputtered. The ultra-focused primary ion beam is then raster-scanned across the analytical region on the sample to produce a map of element and molecular fragment distribution.

Additional Resources