That's a tough order for an e-beam.  You would be better off with
fixturing that rotates a full 360deg.  If that's not possible, I would
recommend that you experiment with higher temperature, lower pressure,
and a slower deposition rate.  The temperature would increase atomic
mobility at the surface and improve even coverage, the lower pressure
and dep rate would allow more time for atoms to arrange themselves more
uniformly and hopefully get more coverage on the sidewalls.

Dan

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Barrios, Pedro
Sent: Tuesday, January 26, 2010 10:21 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] metal coverage over ridge

Hello all,

I am trying to uniformly cover the top, bottom and sidewalls of a ridge.
The ridge has vertical sidewalls and it would be around 1.5-3um tall and
about 2-50um wide. The only equipment that we can use for this is an
e-beam metal deposition system (i.e, no sputtering, no electroplating).

We have fitted the e-beam system with a rocking stage to facilitate
uniform coverage of this ridge.

The rocking motion can be programmed to do virtually any sequence
we want. We have the stage programmed right now for rocking the
sample to +/-45o with a stop (wait time) at both ends of 1sec.

Although the metal covers the ridge, shadowing effects prevent
the metal from covering it uniformly all around -- especially near
corners. Clearly, this simple sequence is not the best. Since gold
is quite expensive and these experiments require about 1-2um of
gold, I was wondering if any of you have done this and is willing to
share this knowledge with the group.

Finally, do you know of any software that could simulate this type
of process?

Thanks in advance!
P. Barrios