Hello, everyone,

I've got a problem with SU-8 soft-bake as I shift from 2inch silicon wafer to
4inch: some islands form on the surface during soft bake ( start to appear
at 65 Celsius degree, and remain after 95 Celsius baking ). Does this
problem have something to do with contamination on wafer?
At first, I thought it was caused by uneven solvent content of SU-8 stored
for two or three weeks in covered beaker. But I also tried the fresh
photoresist, and got the same result.

Does anyone have some ideas with this?  Please give me some advice.

Thanks a lot !

--
Best Regards,

郑瑞麟

Ruilin Zheng

Address:
Pen-Tung Sah MEMS Research Center,
Xiamen University, Xiamen,361005,
P.R.China