FEI Quanta FEG 250, Руководство пользователя

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System Options: Beam Deceleration
9-70
Beam Deceleration Mode Imaging Procedure
1. Put the sample into the chamber and pump to the HiVac.
In the BDM a sample becomes the electrode. Its position, size, tilt
and surface roughness influence an imaging quality. At optimal
conditions the sample should be symmetrical, planar, have a size
comparable with the detector size, and placed perpendicular to the
column axis. In other conditions a distortion, an astigmatism and a
blurring caused by the chromatic aberration appear. This is even
worse when the Immersion Ratio is higher.
2. Select the suitable HV and find an area of interest. Set the
Eucentric Position (see Chapter 7) and tune an image with the
Tuning module / Lens Alignment and the Beam module /
Stigmator 2D control (see Chapter 4). In various quads get the SE
and BSE images to observe different imaging simultaneously.
3. Click the Mode On button. Gradually raise the Stage Bias,
the SE / BSE image is getting dark / light.
At low magnifications an ETD image should become dark
symmetrically around the window center, in other case the sample
could be tilted.
When a dark area is shifted with an Stage Bias change, the sample
is possibly not parallel with the detector. With the use of the
Compucentric stage rotation / stage tilt try to keep the dark are in
the center of the screen.
Note:
When the retractable vCD detector is inserted, stage tilt is
restricted via the UI. Override it by manual control to keep the dark
area in the center of the screen (for Quanta FEG 450 / 650 only).
Note:
An image shift when changing the Stage Bias could be caused by
imaging near the sample edge or any other edge.
4. Set the Stage Bias considering the sample material (charging
compensation, material contrast) and to optimize the signal. Set
the brightness, contrast and WD according to the requirement.
5. Tune the Tuning module / Lens Alignment and the Beam module
/ Stigmator 2D control (both factors remembers the HV and Stage
Bias last used).
6. Repeat steps 4. and 5. to get the best result.