I have done some etching with this formula, 5%TMAH, 38g/L Silicic Acid, 7g/L
Ammonium persulfate.  After initial mixing, it takes about 6 hours before
the solution becomes clear, I say give it some more time.  Also, etch rates
were reported at ~80um/hr, I was only able to get ~35um/hr.

sm

CPSLO

On Tue, Jul 1, 2008 at 8:59 AM, Mukesh Kumar Gahlawat <
mukesh_gah1@rediffmail.com> wrote:

> Hi all
>
> i am trying to use TMAH+Silicic Acid+ Ammounium persulfate solution for
> protecting Al on Si. But i am not able to dissolve Silicic acid in 5% TMAH
> Solution. i have tried at 80 C nd 120 C for about one hour without any
> result. can anybody help me in this matter.
>
> Mukesh Kumar

--
Steven Meredith

http://www.calpoly.edu/~smeredit/index.htm