Forgot to mention, the problematic die that had poor adhesion during lift-off
did undergo standard organic solvent spin cleans prior to spinning PR and
patterning. It was only the additional initial acid cleans that really solved
the problem.

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On
Behalf Of Wilson, Thomas
Sent: Thursday, January 15, 2009 7:01 PM
To: General MEMS discussion
Subject: Re: [mems-talk] Lifting-Off 1um metal

I once experienced adhesion problems with sputtered aluminum (~100-nm thick)
onto polished single crystal (100) silicon die. It turned out that only the bare
silicon die with poor silicon/aluminum lift-off adhesion, had been stored in
plastic containers (black plastic 4x4 snap clip packs) for over one month ...
apparently the plastic out-gassed onto the silicon. Other die from the same
plastic containers, when cleaned in a 1-minute piranha followed by an 10-sec HF
dip, had excellent adhesion after liftoff.


Thomas