Thanks Felex but for most part of the oxide it is gone.
Maybe a bad supplier or some complicated oven process in the bonding process for
the SOI before the wafers were delivered to me.  I still dont know but each
of these factors can be the cause; i guess...

thanks again Felix
nimo


________________________________
From: Felix Lu 
To: General MEMS discussion 
Sent: Tue, July 20, 2010 2:55:17 PM
Subject: [mems-talk] Some silicon-dioxide will not etch in BHF...can that be?

Hi Nimo,

  Two things come to mind:

1. You might need more BHF?
2. Bubbles may be preventing the BHF from reaching certain areas?

Good luck!

Felix