Switching exposure current
We often want to write big pads with a high current, and small features with a much smaller current. Switching the beam current is easy on the ebpg - we just choose the "beam file" in cjob. Here are a few tips for making this very reliable.
The highest beam currents, > 100 nA, sometimes drift out of alignment, and so the ebpg will do an automatic gun alignment for large currents. After you load a current file (to test it),
pg arc restore beam 200na_400
you can also realign the gun manually:
pg adjust beam align
mcur
Next, test the field calibration with
pg sel pattern .....gpf
aeb
You should test the high current beam file, since that is the one most likely to fail. Note that you should NEVER save a beam archive file. Saving a beam archive file would lead to a lot of chaos and confusion, and the system administrator will not be happy about it.
Important trick: When you set up a high/low current exposure, do the high-current pattern first. That way you will see it fail immediately, and you can restart the exposure without ruining the substrate. In cjob, the exposure order will be from LEFT to RIGHT:
If the high-current setup fails, then you can try using a lower current or a smaller block size. And be sure to report the problem.