Hi,

my experience with Polystyrene is that it starts to get soft at
~60-70 °C. So I would double-check that the type of Polystyrene you
use can stand the soft-baking/cross-linking temperature
(typically 95 °C) without melting and mixing with the SU-8 and
SU-8 solvent on top.

Regards,
Michi

On 04/21/2011 04:07 AM, Shane GUO wrote:
> Hello everyone,
>
> Glad to join this group full of knowledgable people. I am a starter in
> microfabrication using SU-8.  I have met a couple of issues in my first stage
of
> work. I first coated the Si wafer with Polystyrene as an anti-adhesion layer
and
> then spin coated SU-8. The following are the issues I met.
>
> 1. I followed the SU-8 50 manual provided by Microchem to spin coat 100um film
> on a silicon wafer which was already coated with a thin layer of Polystyrene.
> After soft bake, the wafer was exposed under UV light using contact printing.
I
> found the wafer stuck to the mask. I pulled them apart carefully using
tweezers,
> finding out some SU-8 residues on the mask. Is this a common issue in contact
> printing or not? Can I prevent this from happening in contact printing? What
can
> be an effective way to clean the SU-8 residues without bringing damage to the
> mask?
>
> 2. My first spin coating of SU-8 50 to make a 100um layer was not successful
> because of bubbles. Thus I tried to clean the wafer and go through the process
> again. The exposed SU-8 wafer was not baked. I just immersed it in EBR, then
> acetone and IPA to clean it. What I found is the colour of the wafer became
> brown and I can see sth like water marks on the wafer. What is the best way to
> clean exposed SU-8? Am I doing the right thing to clean up the wafer.
>
> Thank you in advance.