I don't know if you can etch all three metals with one chemistry.  However I
have used the following for each film:

Al - Aluminum Etch (phosphoric and acetic acid)
Ni - same as above
Au- Transene TFA (iodine, potassium iodide solution)

>>> "Abang Annuar Ehsan"  01/15/01 06:55PM >>>
Hi,

I need to find out how to etch Al-Ni-Au using wet chemical etching
technique, where the metals are stacked on top of one another? what are
the suitable solutions to etch them at once? The process was done using
e-beam evaporator.

Thank you,
annuar.