Frank,

Don't know if this will help you much but it is something I experimented to
remove the edge bead out of a wafer coated with 20um of bcb.  After your
sample is coated with resist take it out of the spinner for a second and
dispense a solvent on the center backside of your wafer (not much, otherwise
it will go into your top side).  Put it back on the spinner and spin at
about 20-30 sec at a speed slower than your coating speed.  This worked
pretty good for me to eliminate backside bcb contamination as well as the
topside edge bead.

good luck!

Lester López
Research Assistant
Microwave and Wireless Research Center
University of South Florida
4202 East Fowler Avenue, ENB 118
Tampa, Florida 33620
PH: 813-974-4851
FAX: 813-974-5250
Email: lelopez@eng.usf.edu
----- Original Message -----
From: "frank berisford" 
To: 
Sent: Monday, March 17, 2003 8:44 AM
Subject: Re: [mems-talk] Bubbles in my SU-8 (Solved!)


> I did some experiments of my own on Friday and was able to get 1 good
bubble
> free coating.  By using a plastic pippette with about 2cm cut off the end
to
> increase the opening's size I put the pippette into the SU-8 just deep
enough
> so the SU-8 can be pulled in.  From here I placed the pippette in close
proximity
> to the wafer being sure to squeeze out any air before dispensing and being
sure
> not to squeeze out any air afterwards.  This had to be repeated about 5
times
> for a 3" wafer and the pippette that I'm using.
>
> Now, I must work on this edge bead.
>
> Thanks for your reply,
> Frank Berisford
>
>
> >Dear Frank Berisford
> >
> >I put the SU-8 resist into a sonic bath with a degas cycle to removed
> >dissolved gases. This cycle pulses the sonics, assisting the nucleation
> >of these gases. About 5 minutes of pulsed sonics at full power and 40
> >C, gives (nearly) bubble-free coatings.
> >
> >Regards,
> >
> >Chris Blanford
> >--
> >Christopher F. Blanford
> >Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK
> >Phone: +44 (0)1865 282603; Fax: +44 (0)1865 272690
> >PGP keyID: 8D830BC9  http://pgp.mit.edu/
>
>
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