FEI Quanta FEG 250, Руководство пользователя

Страница: 118 / 228

Stages: Stages Types and Accessories
7-4
EUCENTRIC POSITION
This should be adjusted after loading any new sample (other than wafer)
or for the greatest accuracy, as the sample loading procedure clears all
position informations. At the eucentric position, one can use various
system components (such as the EDX) in a safe and optimal way.
FIGURE 7-5 EUCENTRIC POSITION PRINCIPLE
At the eucentric position the stage tilt and the electron beam axes
intersect. When the stage is tilted or rotated in any direction, this point
remains focused and almost does not shift.
Finding Eucentric Position Procedure
1. Apply the Stage menu / Auto Beam Shift Zero function.
2. Display the Window menu / Center Cross ( Shift + F5 ).
3. Focus an image. Link Z to FWD and go to 10 mm WD.
4. Set stage tilt to 0°.
5. Using the Z-control, coarsely focus the image.
6. Set the magnification to 1000×, find a recognizable feature and
center it under the yellow cross by moving the stage.
7. Watching the feature, change the stage tilt to 15°. Using the Z-
control, bring the feature back under the cross.
8. Change the stage tilt again to 30°, and bring the same feature back
under the cross using the Z-control.
9. Change the tilt to 0°. The feature should not shift significantly. If the
shift is > 5 µm, repeat steps 6 to 9.
Note:
Described eucentric position procedure is valid for 50 mm stages.
3) Tilting the stage does not move the point of interest out
of the beam.
1) The point of interest is focused below the Eucentric
point (see 2).
Eucentric position
Tilt
Eucentric position
Z adjustment
Stage
Stage
2) Tilting the stage moves the point of interest out of the
beam.
Stage
Beam Beam
Beam
Point of interest
Point of interest
Eucentric position
and Point of interest
Feature is at
eucentric position.
Stage
Beam
1) The point of interest is focused at the Eucentric point
(see 4).