The mechanism for the effect you are talking about is a gold-silicon eutectic
interaction.  The "recipe" for this is not complicated - to get the effect to
occur, you will simply need to heat the substrate to >363ºC (the eutectic
point).

At this point, the elevated temperature will cause interdiffusion between
silicon and gold, and when the local proportion of gold and silicon reach the
appropriate point, the combination will liquefy - this liquid will be able to
mechanically bind the gold layer to the silicon layer.

The higher a temperature you use, the broader the range of Si-Au proportions
that will melt.  However, you also run the risk of all of the material becoming
a gold-silicon alloy, or of the gold to diffuse completely into the silicon
substrate.

Best Regards,
Chad Brubaker

EV Group
invent * innovate * implement
Senior Process Technology Engineer - Direct: +1 (480) 305 2414, Main: +1 (480)
305 2400 Fax: +1 (480) 305 2401
Cell: +1 (602) 321 6071
E-Mail: [email protected], Web: www.EVGroup.com

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Moshe
Sent: Saturday, May 10, 2008 11:41 AM
To: [email protected]
Subject: [mems-talk] Gold evaporation coating on silicon - thermal treatmentfor
adhesion

Last week I asked about an adhesion coating achieved
between gold and silicon.

Since then I've heard about a  different way to achieve that.

I talked about thermal treatment so the gold coating
absorb to the silicon, at that way the adhesion obtain
with no third layer.

The general thermal treatment recipe is heating to 400
Celsius degrees for few hours in inert environment.
Has anyone done that before?

Whet is the exact recipe for this treatment ?