System Options: Plasma Cleaner
C O N F I D E N T I A L – FEI Limited Rights Data 7-43
Plasma Cleaner
The Tool s menu / Sample Cleaning item starts the Sample Cleaning
procedure, which is an efficient process for removing very thin
contamination layers, which are typically formed by hydrocarbons
residues remaining on vacuum parts after conventional cleaning or
could be transferred into the microscope chamber with a sample.
The plasma cleaner generates free oxygen radicals, which react with
hydrocarbon molecules on the surfaces to form CO, CO
2
, and H
2
O
molecules that can be pumped away. It is operated at special vacuum
conditions (~tens of Pa) similar to the Low Vacuum mode.
FIGURE 7-15 Plasma Cleaner
The Sample Cleaning procedure uses settings from the Plasma Cleaning
Alignment (see Chapter 4).
For avoiding of typical “weak” contamination artefacts during high
resolution imaging (image darkening), 1–2 minutes plasma cleaning
duration in combination with cryo cleaning should be sufficient. When
bulky deposition is visible (mostly on image corners), 5 minutes
duration is recommended.
Note
Porous, biological or hydrocarbon based samples cannot typically be viewed
without presence of contamination artefacts even after plasma cleaning,
which is caused by presence of contamination source in the sample itself.
Sometimes, poor image quality can be caused by electron beam etching and
re-deposition of etched material also.
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