Awhile ago, I posted a request for information on purchasing a SEM
lithography system. I have finally summarized what people emailed me and
what I learned while purchasing this machine.

  A SEM lithography system is a SEM with an add-on control system for
lithography. Almost all academic e-beam lithography is done this way.
And it works. Lots of groups routinely do 50 nm lithography in PMMA with
these machines.

 There are two suppliers of the add-on control hardware/software for
e-beam lithography: Raith and Nabity (see their web pages). Raith sells
a full product line, from the low end add-on controller to turn-key
e-beam lithography machines with laser stages. I am only going to
discuss what we were interested in: e-beam lithography over small areas.
(The Nabity system and the Raith Quantum). The interesting thing is that
the installed base for these two systems are very geographic: Raith is
Europe and Nabity is North America. Since I'm in North America, most of
the people I talked to were Nabity users. Both systems appear to be
comparible, both in price and operating characterisitics. The Nabity
system has a large happy customer base, while I had difficulty
contacting the Raith customer base.

  My comments on which SEM to purchase are strongly based on my
conversations with Joe Nabity. He has been very helpful in giving advice
on what is needed in an SEM. We are users of e-beam lithography. That
is, we want to make structures, but we are not interested in doing R and
D in ebeam lithography. For this reason (and financial ones), we did not
look at FE-SEM based e-beam lithography. It just seems to me that it
will take a few years for all the instrument bugs to be worked out with
Fe-SEMs.

  For our needs the perfect machine is a high end LaB6, 40 KV SEM. The
problem is that with the advent of FE-SEMs, most of the microscope
manufacturers no longer manufacture high end SEMs that are not FESEMs.
The only two left are Phillips and LEO. And LEO is ending the
manufacturing of their machine. This leaves either the purchase of a new
Phillips or the purchase of a used SEM. Used SEMs will do the job, it
just not as nice looking as a new one. We hope to go with a new machine.


    Ken Westra
    Manager/Staff Scientist
    MicroFab at the University of Alberta