Leon,

     Plasma bonding is a relatively low temperature operation.  Think up
to 50 degrees C.  I know that silicon wafers can be successfully bonded.
Not sure about Sapphire, Aluminum, Silicon but we could do tests for
you.  Bill Moffat

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Leon Maurer
Sent: Monday, July 06, 2009 7:42 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Al-Si wafer bonding

Howdy,

I'm looking for information on Al-Si wafer bonding, and I saw a good
thread here from 2002 about why I don't want to do it, so I was
wondering if there was equally good information here about how to do it
if I had to.

I'm new to wafer bonding, and the papers I've found that mention it
haven't been too informative (although perhaps I haven't found the right
papers). One issue is that the wafer bonding setup I have access to only
goes up to 550C, and for various reasons (including that we'd eventually
like to bond sapphire to Si with an intermediate Al layer
-- my understanding is that the differences in thermal expansion rates
can cause trouble) we'd like to avoid temperatures that high.

We don't need particularly strong bonding -- mostly it just has to
survive (man)handing during the rest of fabrication (which will involve
some lithography and etching). However, the bond or two I've made so far
aren't cutting it (200C, 2.5MPa, 30min, they fail if you look at them
funny). Anyone know what strengths can be achieved at different
temperatures/pressures/times? Any tricks that could make things go more
smoothly? Other advice?

Thanks.
-Leon