I am using SU8 GM 1070, 70um thikness, soft baked by datasheet.

I am exposing a relatevly large area on 4" wafer and during development the exposed SU8 area peels off.

The resist is span on a copper seed layer.

I have tried to change the PEB temp, the PEB time, to use an adhesion promoter, to use several expose doses, nothing helps. I am using standart Mask Aligner system with 375nm wavelenght.

The interesting thing is that when I do the exactly the same process on half wafer - the development looks fine, but when I use the same parameters on full 4" wafer, the resist peels off.

Anyone can help ?

Thank you.