Hi Matteo
The fractals you see mean that you have successfully created a eutectic
layer. If you need a secular gold coating, you can try to sputter gold onto
the Silicon with sputter etch before deposition so you get micro-roughness
that will improve adhesion.
Another way is to use evaporation with ion beam etch before to get the same
effect although sputtering will give better adhesion. If you budget /
facility is better, you can try ion assisted deposition etc.
All of these are possible but not easy!
Shay

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Matteo Dainese
Sent: Wednesday, September 05, 2007 9:32 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Au clustering

Hello,
In a fabrication process I'm running now I have an 200nm Au film deposited
on a Si substrate. The process doesn't allow me to use adhesion layers like
Ti or Cr so I was trying to improve the adhesion of Au to Si by heating in a
convection oven in the nearby of the Au-Si eutectic temperature, in order to
generate the necessary intermixing at the interface which is usually used in
the standard Au-Si eutectic bond.
On the other hand what I observe after the oven treatment is the
considerable formation of Au agglomerates on the surface, which look
sometimes like geometrical fractals.
Has anybody seen something similar and knows how to avoid it, or this whole
approach is just a bad idea?