Hi Weidong,

   You shouldn't have a problem with the aspect ratio you have given.
Sometimes after a DRIE etch you might have a polymer residue preventing you
from etching the oxide underneath.  An oxygen plasma can normally remove
this polymer.  One way of determining where in your structure you still have
oxide is by using a microscope with an IR camera.

Phil Tabada


>From: 
>Reply-To: General MEMS discussion 
>To: mems-talk@memsnet.org
>Subject: [mems-talk] HF solution releasing the SOI
>Date: Sat, 24 Jul 2004 10:12:42 +0800
>
>Dear colleges,
>      I use 80um thick device layer SOI wafer to fabricate a MEMS structure
>with DRIE. The box layer is 1.2um thick.The trenches in the structure is
>80um deep and 5um wide.When I release the structure with HF solution, I
>find it can't be released after many hours!what is the problem? The
>depth/width ratio is too high?
>Thanks for your possible help!
>                                                                Weidong
>Shen
>                                                       Zhejiang
>University,Hangzhou,P.R.China
>
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