Nik,

If you'll buy that process and etch "tool", I have some ocean front
property in Arizona I'll sell you for cheap.  There's another guy who'll
sell you a expensive piece of equipment to do image reversal the hard
way, which you will surely need.

You might want first read the original papers on the fabrication of
silicon nitride AFM probes:

Albrecht, Akamine, Carver and Quate "Microfabrication of cantilever
styli for the atomic force microscope", JVST A 8 (4) Jul/Aug 1990
p.3386-3396

Akamine and Quate "Low temperature thermal oxidation sharpening of
microcast tips" JVST A 10(5) Sept/Oct 1992 p. 2307-2310

Roger Shile

-----Original Message-----

NIk:

I will guess along with you with respect to formation of silicon nitride
afm
tips. I would assume a starting point of say 4-700 angstroms of silicon

dioxide on a prime silicon wafer followed by whatever thickness of
silicon
nitride you eventually want to create somewhere around 1 micron I would
think  would
be good. Using a positive photoresist with a pattern of circles to a
thickness of around 1 micron do a standard photo processing sequence
with coat  bake
align develop. At this point you will want to reflow your photoresist
pattern
using a hot plate in a nitrogen box. This would work better if you can
pull
vacuum on the wafer to the hot plate. You will need to find out thru
testing
at what temperature you will get a true flow of the resist. With some
testing
you should be able to get a rounded feature somewhere around 50 degrees
from
vertical. Once completed you will need to develop a plasma etch process
that
will yield as close to 1:1 selectivity of the photoresist to the silicon

nitride. This might be accomplished using SF6 + Oxygen + Nitrogen in an
ICP/RIE
type system. I would use SF6 because it will be more aggressive to
silicon
nitride than say CF4. Once you determine the etch rates for photoresist
and
silicon nitride you would just run the process until all of the
photoresist is
gone. This should leave a nice sharp silicon nitride point for your AFM
tips.

We have a plasma etch tool that I described above but there are
engineering
costs and other charges required for use if you want to actually make
some of
these devices. Good luck Bob Henderson