Hi Joshi,

        just increase your silicic acid amount. silicic  acid is used
to protect aluminum and AP is used to avoid hillock formation and to
produce smooth surface.... you can write to me if you want more
details. Also tell me the following details,

   1) How you are making 5% TMAH solution? are you making 5% TMAH
solution from a standard 25%TMAH solution available commercially?

   2) How many grams/litr silicic acid you are adding to your TMAHW solution?

      If you are doing everything as per literature, then better
change your silicic acid or TMAH solution...

Regards,
A. Ravi Shankar,
Research Scholar,
Microelectronics Lab,
Electronics & ECE Department,
IIT Kharagpur.