Hi Hoyin,
Y-C Tai's group (from CalTech) presented a couple of papers with
free-staanding parylene beams at MEMS 2002. It appears they used dry
etching to release their beams (BrF3 etching polysilicon). Perhaps they
have some insight on wet releasing.

Jesse Fowler
  UCLA/MAE Dept., 420 Westwood Plaza, Room 18-121, ENGR IV
  Los Angeles, CA 90095-1597 | (310)825-3977
"Battery is safe if not provoked." -- _Batteries in a Portable World_

On Tue, 26 Mar 2002, Chan Ho Yin wrote:

> Hi Mighty,
>
>     Thank you for your help first!!!
>
>   On top of Al, I have deposited polymer Parylene. I guess may be you are
> right. I can see that the beam bends.  But my problem is that I can see the
> beam floating on the solution, with one end fixed on the substrate. I don't
> know whether you can understand or not.  Let's say, when I shake the bottle
> with solution inside, the beam cannot withstand the fuild flow and vibrate
> to and fro. In fact, I am not shaking the bottle. I've just pulled the
> substrate out. I should say.. the beam will follow the fuild motion. Hope
> you can understand. My english is not good enough!!!
>
>   Thank you very much!!!!
>
> Yours,
> Hoyin
>
>
> >From: Mighty Platypus 
> >Reply-To: mems-talk@memsnet.org
> >To: mems-talk@memsnet.org
> >Subject: Re: [mems-talk] Sacrifical release
> >Date: Tue, 26 Mar 2002 07:22:02 -0800 (PST)
> >
> >Greetings Chan Ho,
> >What you're probably seeing is the result of film stress, not any sort of
> >fluid force. You'll probably be able to find some information about stress
> >reduction in Madou, Kovacs, Trimmer, or possibly even Maluf. By the way,
> >what material are you depositing on top of Aluminum (to make your beams)?
> >
> >Jesse Fowler
> >   UCLA/MAE Dept., 420 Westwood Plaza, Room 18-121, ENGR IV
> >   Los Angeles, CA 90095-1597 | (310)825-3977
> >"Battery is safe if not provoked." -- _Batteries in a Portable World_
> >
> >On Tue, 26 Mar 2002, Chan Ho Yin wrote:
> >
> > > 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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> > > !C
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>
>
>
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