Hi mukesh,

      can you tell more details about yor process parameter? in
general, if the temperature of tmah bath is more then silicic acid
will dissolve faster in tmah solution. Also it depends on silicic acid
contents. for us 40 gms/ltr silicic acid takes approx. 3 hours to get
dissolved in 5%TMAH solution at 85 deg celcius. i.e around 250 ml of
5% TMAH and 10 gms of silicic acid. we had experienced similar kind of
problem what you are facing now. it may be due to shelf life of either
TMAH or silicic acid. repeat ur experiments by changing either tmah or
silicic acid. if you still find problem, feel free to contact mde..

--ravi shankar.