At 07:09 PM 11/4/2004 +0100, you wrote:
>Dear all,
>
>I am in the process of running in an existing SU-8 process in a new
cleanroom, and I have come across a problem I have never seen before. After
spin coating the SU-8 looks fine, but during softbake the resist dewets on
the surface. It pulls away from the wafer edges and form isolated drops on
the wafer.
>
>I think my process parameters are fairly normal:
>1. 30 minutes in an oven at 200 deg. C to dehydrate the silicon wafer.
>2. Let cool to room temperature.
>3. Spin coat as per datasheet.
>4. place on the 65 deg. C hotplate as per datasheet. (this is when it dewets)
>......
>
>Normally this gives great results, but not in the new cleanroom.
>Have anyone seen SU-8 dewet on wafers? And have you found out the cause?
>
>My current thinking is along the lines of surface contamination from the
oven, or a low air humidity in the cleanroom.
>
>Any input is appreciated.
>
>Jacques Jonsmann
>

I'd lean towards wafer contamination, either via the oven or previous
handling.
Did you do a piranha etch beforehand?
The other possibility is contamination of your SU-8.

How new of a cleanroom?

--
Mark Fuller
Microelectronics Fabrication Facility
Washington State University
Dana Hall 102
Pullman, WA  99164-2711
(509)335-1797