FEI Quanta FEG 250, User'S Operation Manual, Page: 42 / 228

Software Control: xT microscope Control Software
4-14
settings. Only one is active at any time, but can be operated
independently for each quad.
Degauss (F8)
triggers the procedure which puts all actually used electron lenses to
a normalized state by removing their hysteresis effects. For a few
seconds while the procedure is running all live images disappear or
turn fuzzy, and then return back.
Use this function with (almost) focused image to obtain the most
accurate Magnification, Horizontal Field Width (HFW) and Working
Distance (WD) readouts.
Lens Alignment (Shift + F4)
This feature activates / deactivates the final lens alignment mode for
the fine alignment. The scanning changes to the fastest scan value,
lens modulator turns on and the alignment cross appears in the center
of all imaging quads.
Pressing mouse button activates a 4-arrow ended cursor. The mouse
motion starts the final lens alignment (see Chapter 6).
The Stage Menu (Alt + S)
opens the stage and sample navigation functions (see Chapter 7):
xT Align Feature
opens a procedure that helps to navigate along a feature that extends
off the screen at the desired magnification.
Compucentric Rotation (F12)
places a green circle in the active quad. By rotating the circle a
different viewing orientation of the sample area can be achieved by a
physical stage rotation and adjustment of X and Y axes. Stage rotation
keeps the observed feature in the center of the field of view. If this
does not occur, the alignment should be performed to locate the stage
center and calibrate the stage (see Chapter 6).
Define User Units…
activates a procedure guiding the user to determine User Units for X
and Y stage axes. These are used for relative stage movements
associated with the regular features mapping (in particular integrated
circuit applications).
User Units
organises the stage software to recognise the defined user units
rather than the default metric measurements. The X and Y
coordinates now operate in User Units which are indicated in the
Stage module / Coordinates tab by the UU symbol.
Clamp
toggles on / off a mechanical stage clamp in order to prevent stage
vibrations during high resolution imaging.This menu item is greyed out
on systems without a securing Clamp (50 mm stage).
Beam Shift Reset
zeroes the beam shift. A feature observed with a non-zero Beam Shift
is automatically moved back to the image center using the stage.
Zero Beam Shift
zeroes the beam shift without moving the stage. A feature observed
before selecting this function is moved from its position by the
measure of the applied beam shift.