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.