Dear  Colleagues,

I was wondering about the stability of Copper in an 8-25% TMAH solution at
around 80C.

The copper is 20nm thick an sitting on a SixNy-layer and serves as a  seed
layer for Nickel.
The adhesion here is pretty good.
The electroplated Ni-structure is around 1um thick.
After the electroplating I removed the copper where no Nickel was present  in
a 0.1mol HNO3 solution.
So far so good.
Now I want to back etch the silicon wafer in TMAH.

Will the TMAH underetch the Nickel and remove the Copper?
Maybe someone has a suggestion to protect the copper by additives  etc.

Regards,

Sebastian