I would consider that the Cr has diffused into the Aluminum during the metal
deposition steps.

Ed

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Aaron Datesman
Sent: Wednesday, January 13, 2010 1:09 PM
To: General MEMS discussion
Subject: [mems-talk] Use of Cr mask for Al RIE


Hi All -

I am trying to etch 300nm Al on Si using Cr as an etch mask. The etching
tool is an Oxford PlasmaLab ICPRIE, using HBr chemistry.

I find that this works pretty well, but due (I presume) to an
electrochemical effect, the Al does not etch completely at all locations
near the Cr mask. So, I wonder: has anybody tried this before? Any
suggestions?

(I'm attempting this etch in order to pattern two masks simultaneously
on one layer of Al: the first mask in negative by liftoff of Cr, the
second mask in positive tone with photoresist.)

Thanks!

Dr. Aaron Datesman