Dear Barry,
The formation of a insulating layer (may be Al oxide, may be something
else) on your Al may be linked to the way you open the oxide pads. If
you use a wet BOE or dedicated pad etch, an Al hydroxide or
hydrofluoride layer can be formed. If you use HF gas, a quite stable Al
fluoride layer is formed. If RIE is applied, a fluoride layer may also
be formed depending on your process conditions. Also, you have to take
care about the possibility of electrochemical corrosion of the Al after
processing. This can happen, when there are other metals or higly doped
Si areas in contact to the Al and exposed to air, or if metalized wafers
are placed for too long time in humid air or rinsing baths. You see, it
can be a quite complex issue.
In case that you need further foundry services, let me know. We can also
do the job.
Best regards,
Joern Koblitz
******************************
Joern Koblitz
microFAB Bremen GmbH - the MEMS wafer foundry
Universitaetsallee 5
D-28359 Bremen, Germany
Phone: +49 421 24 100 0
Fax: +49 421 24 100 99
eMail: [email protected]
website: www.microfab.de
******************************
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Posted At: Friday, March 29, 2002 6:08 PM
Posted To: MEMS-talk
Conversation: [mems-talk] Al oxide removal
Subject: [mems-talk] Al oxide removal
Dear MEMS coworkers,
We currently utilize foundry service to fabricate our MEMS platform, and
we
functionalize the platform by coating a proprietary material. The
existing
platform design calls for, fresh out of foundry, a SiO2 top layer with
contact openings to the underlying Al.
The issue we run into is that the exposed Al is easily oxidized and the
contact resistance varies from sample to sample. We have tried using
chemistry removing the aluminum oxide layer prior to functionalization.
Yet
the oxidation happens so rapidly that a thin insulating oxide is formed
between sample transfer (in air), so we alleviated but not eliminated
the
reproducibility difficulty.
I appreciate any insights.
Regards,
Barry Chen
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