I do not quite understand your process, but here is what CAN
happen in some devices:
When you take the device out of the rinse, a small amount of
liquid is trapped between beam and substrate. Its surface
tension will bend the beam towards the substrate. If the beam
touches the substrate, it might stay there even when the liquid
is evaporated, due to stiction (which is a big issue in many
micromechanical devices).
Here are some ways to verify this:
- If you can, check if the beam is straigt BEFORE taking out
   of the solution and only bends AFTER taking out. If so, you
   clearly have surface tension induced forces as you suspected.
   Of course, this is not easy to check unless you place the
   bath under a microscope.
- Does your beam touch the substrate AFTER the liquid evaporated
   fully (bake it thoroughly)? If NOT, you probably have film
   stress induced forces, since stiction only happens on contact.
Hope this helps.

Greetings,
        Frank Berauer
        Senior R&D Engineer
        Hewlett-Packard Singapore


-----Original Message-----
From: Chan Ho Yin [mailto:hoyincym@hotmail.com]
Sent: Tuesday, March 26, 2002 8:49 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Sacrifical release


Hi all,

     I am a beginner in MEMS field and I am now fabricating a simple
cantilever beam. The sacrifical layer is Al (~2um). The beam thickness is
~0.5um and length is ~500um.   When I tried to release the structure using
AZ300 PR developer, I found that the released beam will bent or twist due
to the force caused by the fluid flow (PR developer).

   Even I hold the sample carefully, the beam still bent or twist when I
tried to pull the sample out of the solution. It can't stand straight. What
should I do? Is there any technique in handling this??  I guess this might
too simple to you. But it is important to me.  Can you suggest me with
detailed steps?  Thank you very much!!!!

Yours,
Hoyin



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