scaccag at stanford.edu
Sat Aug 14 19:04:10 PDT 2004
today I and John (Cumings) tried again alignment and write.
The problem of the elongated spot is still there and here are some
commetns about it, that will be useful (hopefully) for diagnosis:
1. The elongation is always along the Y direction and is more pronounced
at low mag. It does not seem to depend directly on mag2/mag3, but starts
to be apparent at ~4000-5000X.
2. It is directly correlated to the Y scan direction: if rotation scan is
enabled on LEO, also the elongation rotates.
3. The elongation also seems to depends on how long you leave the beam in
spot-size mode, when burning the spot at low-mag.
4. John wrote at 1200X and managed to do the align writefield. I tried to
align at 600x (100um WF), but the slow-scanned images appear noisy in the
Y direction, like broken. We have some pictures of this and of the
elongated spot, but they are still on the raith computer, since it's not
networked and had no time to burn a CD.
I was not able to do an align writefiled procedure at 600X
using 0.6x0.6um writefield (the image was very noisy), but I did it at 1200X.
I gave it a shot and started writing at 1200X (50um WF), but I don't
expect great results, but I'm convinced the system HAS a problem and
something needs to be done.
John has an interesting theory about that: there sould be some noise in Y
scan deflector or somewhere else, but that affect only the Y direction.
When going at low mag the gain is increased and so also the noise which
gives rise to random displacement of the beam. This would be consistent
with both elongated spot and noisy images during WF alignment.
Anyway John can tell you more about this theory, on monday.
More when I'll develop my sample.
More information about the raith