Using the secondary electron detector
The EBPG 5200 has four unbiased scintillator detectors, like the older 5000. High-energy scattered electrons will be detected if they happen to hit one of the scintillators. Additionally, one of these detectors has a sock-shaped grid which can be biased positively, to attract lower energy secondary electrons. It can act just like an Everhart-Thornley detector on a SEM. The bias voltage causes a little distortion in the field, but not much.
If you ever feel the need to use resist itself as an alignment mark, or if you need a better image from a weak alignment mark under thick resist, you can try turning on the bias with the command
sed_on
which is easier to remember than the lines
pg set detect 2
pg set sed on
It takes about five minutes to ramp up the voltage. (The long turn-on time is completely pointless. But for now we have to live with it.) When you are done, you should turn off the bias, so you will not confuse the next user. Just type
sed_off
This is important, so on our 5200 we have included it in "subu". This automatic shut-off can be overridden by using
subu 4 sed_on
instead of
subu 4