4.4 Troubleshooting
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The second is random noise caused by unstable probe current or unstable detector.
For example, bright spots or bright or dark lines appear when emission current is unstable or the
scintillator of the secondary electron detector has been damaged.
If images show such a noise, check the following.
(1) Is the emission current too low?
Reset the accelerating voltage, the filament, and the gun bias.
See <3.3.2 Setting the Accelerating Voltage and Filament Current>.
(2) If the filament setting off?
If the filament setting is off the saturation point, the emission current may fluctuate, in
which case the filament should be reset.
See <3.3.2 Setting the Accelerating Voltage and Filament Current>.
(3) Select the BSE detector to check the noise level. If there is no noise, the problem may lie
with the SE detector itself, such as a specimen charge-up problem.
The third is random noise caused by partial charging of a specimen.
Observe another area of specimen or surface of a specimen stub. If noise does not appear,
your specimen may be charged. Select operating conditions for such charged samples or apply
a suitable preparation to your specimen to eliminate charging.
4.4.6 When You cannot Correct Astigmatism
If astigmatism still remains at the maximum correction level (One (and/or both) of Stigma sliders
is set at the maximum or the minimum, or one (and/or both) of Stigma knobs on the operation
panel is full), check the following.
(1) Open the Alignment dialog window and start Aperture Alignment mode. If image is
wobbling, carry out aperture alignment.
(2) Use another opening of the objective lens aperture. If you can correct astigmatism, use
the opening or conduct cleaning of the aperture plate referring to the instruction manual.
(3) If astigmatism correction is difficult due to shift of image during correction, open the
Alignment dialog window and carry out Aperture alignment and Stigma alignment.
If you still have troubles, contact a service engineer.
