My guessing...you may need IPA instead of acetone to rinse after the
development. Acetone dissolves the un-cross linked SU8 and leaves something
on your wafer.

Good luck,

Hongjun Zeng, PhD
Microfabrication Application Laboratory (MAL)

-----Original Message-----
From: Nan Xie
Sent: Tuesday, April 19, 2005 7:44 PM
To: MEMSTalk
Subject: [mems-talk] SU-8 Developing Issue, advice required

I am developing SU-8 2050 after spun around 50um.
My procedures for soft baking, exposure, and PEB are correct.
I am having trouble getting clean develops after about 6min and 2-3s acetone
spray.
What I am getting are some milky residue around my features. I understand I
need to develop it more when this occurs, but this milky residue still
remains or the SU-8 would come off.

Anyone have any suggestions? Maybe I need to expose more?