Usually people will first doped the TMAH with Si before
etching the wafer. The dissolved Si will form a passive
layer on the Al to protect it form etching.

A popular forumla is TMAH(25%) : H2O : Si : (NH4)2S2O8 ( 200
g : 800 g : 16 g : 5 g ). I have tried it before and it
works!

First you have to put 2 635um Si wafer into 200ml TMAH
solution and 800ml H20 at 85oC until all the Si is
completely dissoved. It takes about 1 days. After that add
5g of (NH4)2S2O8 into the mixtures. Then the solution is
ready to use. Remember, use the solution as soon as
possible, because the lifetime of the solution is quite
short (1-2days).

Enjoy!

> Dear MEMS members,
>
> I am looking for the information regarding TMAH
> etching that does not attack Al bond pads.
>
> can i get any article regarding this.
>
> Your suggestions would be highly helpful.
>
> thanks
> Kris
>
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Best Regards,
Kin