Hello folks !

I have a question related to metal etching. I want to etch my Cu seed layer
(100 nm by sputtering). Its a bit tricky since I also have about 100 nm of
Ni and 100 nm of Ag on my wafer which I want to keep. I have tried 10%
nitric acid at room temperature, but it etches Cu and Ni at almost the same
rate, though silver is not etched significantly. I have also tested 10% HCl
and i observed the loss of adhesion of some Ni structures (strange!) and Cu
was not etched significantly. When the sample was taken out of HCl, it
oxidized and Cu color changed to purple shades. I would appreciate if
someone can recommend some wet etchants that can selectively etch Cu and
have low etch rate for Ni and Ag.

Cheers,

Bilal

Helsinki University of Technology,
FINLAND.