Hi Alex, in a couple of weeks we are going to do the same thing using
a FEI Helios dual-beam and pmma, maybe we can exchange experiences!
  Why are you going to image the area at low kV? I think is not a good
idea because the clearing dose for pmma is inversely proportional to the
acceleration voltage. So you will better do it at 30kV, low current and
only a snapshot in the area of interest. You should certainly correct
focus and astigmatism of the beam in a different area that you can
sacrifice.

First we will do a dose test using different dwell times and pitchs in
order to determine the good parameters for the particular substrate, in
our case is high resistivity silicon.

Very important: make sure that the iSPI option of the FEI software is in
PAUSE. We have the experience that when it is not in pause, an array of
dots appears in the pmma layer after development.

Javier


El 18/10/2010 18:08, Alex Mellnik escribió:
> Hi,
>
> I am working on a project where I need to make aligned contacts to
> randomly-distributed nanostructures a few microns across.  My leads and
> alignment need to be to within about 0.25 microns, which is too small for
> the contact aligner I have access too.  I can do aligned ebeam lithography,
> but it seems like overkill when I don't need to push the resolution and each
> alignment is only good for a single set of contacts.  I can put down Pt in
> our dual-beam FIB (
> http://www.fei.com/uploadedFiles/Documents/Content/2006_08_Strat400STEM_Family
_Semi_pb.pdf),
> but eventually I need to make contacts out of other materials.
>
> I am interested in exposing ebeam resist with the electron-beam in our FIB.
> We don't have a dedicated add-on like one of the Raith systems (
> http://www.raith.com/) but can generate patterns with the included
> software.  My plan is to use a resist that requires a high dose (maybe PMMA)
> and image the area that I want to expose briefly at ~2 kV, ramp the beam up
> to 30 kV and expose the region.  Has anyone done anything like this before
> or have any thoughts?
>
> Thanks,
>
> Alex

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