Vickie,

You're going about it in the right way, you just need a different gold etch.
The key, of course, is to pick an etch that will not attack your plated gold
too much.  Try a mixture like this:  900ml DI water, 400ml Hydrochloric acid
and 400ml Nitric acid.   Let it cool to room temp before use.  This will
etch 2000 ang of Au in about 3 minutes.  Once mixed up, it will last for
quite some time (2-3 weeks).  You can etch the TiW in straight H2O2(30%).
Beware undercutting of the TiW.

Jason Tauscher
Silicon Fabrication Engineer
Microvision, Inc.


Message: 6
Date: Wed, 5 Dec 2001 14:25:34 +0800 (HKT)
From: mawei 
To: mems-talk@memsnet.org
Subject: [mems-talk] seed layer for electroplating gold

Hello, everyone,

A problem happened when I did my electroplating gold: Before I do the
electroplating, I sputtered a layer of TiW800A/Au2000A for seed layer. And
the I used the thick PR to be the module for plating gold. After finished
the plating, I removed the PR, and want to remove the seed layer also. The
problem happened when I used KI+I2+H2O to etch the seed layer: Gold. I can
never etch them away clearly. How does it happen? Is it possible that
sputtering gold can't be etch by KI+I2+H2O afer being covered by PR or
being dip in the solution for electroplating?

Thank you for your attension.

Best regards,

Vickie