Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)
Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is a surface analytical technique that focuses a pulsed beam of primary ions onto a sample surface, producing secondary ions in a sputtering process. Analyzing these secondary ions provides information about the molecular and elemental species present on the surface. For example, if there were organic contaminants, such as oils adsorbed on the surface, TOF-SIMS would reveal this information, whereas other techniques may not. Since TOF-SIMS is a survey technique, all the elements in the periodic table, including H, are detected. Moreover, TOF-SIMS can provide mass spectral information; image information in the XY dimension across a sample; and also depth profile information on the Z dimension into a sample. TOF-SIMS can also be used for depth profiling and compliments dynamic SIMS. The advantages for TOF-SIMS for profiling are its small areas capabilities and also its ability to do survey depth profiles.
We could use TOF-SIMS to assist customers with quality control, failure analysis, troubleshooting, process monitoring, and research and development. For example, the information we provide when investigating wafer surface contamination issues can help determine the specific source of the problem, such as pump oils or component outgassing, or it may indicate problems with the wafer-processing step itself (e.g. etch residue).
Ideal Uses for TOF-SIMS Analysis
- Surface microanalysis of organic and inorganic materials
- Mass spectra direct from surfaces
- Ion imaging of surfaces
Relevant Industries for TOF-SIMS Analysis
- Aerospace
- Automotive
- Biomedical/biotechnology
- Compound Semiconductor
- Data Storage
- Defense
- Displays
- Electronics
- Industrial Products
- Lighting
- Pharmaceutical
- Photonics
- Polymer
- Semiconductor
- Solar Photovoltaics
- Telecommunications
Strengths of TOF-SIMS Analysis
- Specific molecular information on thin (sub-monolayer) organic films/contaminants
- Surface analysis that allows more complete characterization of a surface
- Excellent detection limits (ppm) for most elements
- Quantitative element analysis of Si and GaAs
- Probe size ~0.2 µm for imaging
- Insulator and conductor analysis
- Non-destructive
- Depth profiling is possible
- Whole wafers up to 200 mm
Limitations of TOF-SIMS Analysis
- Usually not quantitative without standards
- Samples must be vacuum compatible
- It can be too surface sensitive:
- Sample packaging and prior handling may impact quality of results
- Analysis order is important, surface-damaging tests should be done after TOF-SIMS
- Very surface specific—only examines top couple of monolayer
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