There is a strong electrochemical effect between the two metals. We have
actually used this effect to selectively protect chrome in Cr etch. One
solution may be to bias the chrome, if this is feasible.

-Mike

>>> dumbo_work@yahoo.com 04/10/02 11:51AM >>>
Hi,
I have a question about possible electrochemical
reactions when wet etching Cr/Cu.
Copper is on top of Chrome, so I etch the copper
first, then lithography, and etch the chrome.
I tried 1020 AC and TFD from the Transene, and CR-4.
During etching, I observed that if there is a tiny bit
of copper left exposed to the chrome etchant, the
chrome etchant won't attack the chrome.
Later on I used HCl.  If I touched the chrome with my
stainless steel tweezers, HCl will etch Cr.
I think there are some electrochemical reactions going
on.
Any insights will be greatly appreciated.

Jai
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/
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