Hello Magali,
NiFe electroplating is notorious for showing cupping, or lipping, effects as
the film approaches edges of things like photoresist, or the edge of the
wafer for that matter.
One trick you could try would be to add a 1" strip of copper plating tape to
the outer edges of the wafer, in the area of the problem, to increase the
effective plateable area. Basically what will happen is the uneven plating
will occur out on the tape and not on your wafer. The idea is somewhat
similar to sputter depositing from a 8" target to a 6" wafer to increase
uniformity, but in our example of using tape, the extra 1" around the wafer
is sacrificial.
If you have a more sophisticated cathode arrangement than an alligator clip,
the tape can be replaced by cathode modifications, which will help maintain
wafer to wafer thickness control, since the tape application is likely to
add some variation from run to run.
Regards,
Justin
Justin C. Borski
MEMS Program Manager
Advanced MicroSensors Inc.
(508) 770 - 2088
-----Original Message-----
From: Magali Brunet [mailto:[email protected]]
Sent: Thursday, October 17, 2002 3:58 AM
To: [email protected]
Subject: [mems-talk] Edges problem in through-mask NiFe electroplating
Dear all,
On a silicon wafer where a Cu seed layer is sputtered, I am depositing
photoresist (8um thick) to create patterns and then electroplating NiFe
through the patterns (5um thick).
The deposit has an even thickness except at the edges where there is a
big overplating. (kind of
"dog hears")
Does anyone have an idea on how to get rid of this edge problem?
Thanks a lot in advance,
Magali
--
PEI Technologies,
NMRC, Lee Maltings, University College,
Cork, Ireland.
Tel: +353 21 4 904279
Fax: +353 21 4 270271
email: [email protected]
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