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/