Hi Bob,

I agree with Brad acetone is not best choice. My recommendation is to
try PGMEA as solvent (EBR-Solvent from AZ-Electronics or 1500 Thinner
from Shipley). Additional the position of the nozzle seems to be to
close to the wafer edge. Solvent should cover complete edge bead while
removing.
Good luck.

Regards,
Bernd Krueger

>Hi Bob,
>I think the reason you are seeing an additional bead is the acetone.
>Usually the preferred solvent is the thinner for your photoresist or a
>specific edge-bead solvent sold by most PR suppliers.   Photoresist is
>highly soluble in acetone and it is possible that the fumes  from the
bowl
>are enough to modify the edge profile.   If your PR is thin enough
(below
>0.75 um or so) then you can watch the color of the applied PR film
during
>the EBR step.  If it goes through many color changes, then the acetone
is
>affecting the entire film, which is not a good thing in any case.
Acetone
>is also highly flammable and therefore dangerous to use in a spray mode
>without other precautions.  Also, although I am not familiar
specifically
>with the Suss system, the nozzle for delivery should be at a low angle
and
>the flow of the solvent should not leave an excess of liquid on the
edge of
>the wafer.