Hi,

I'm looking for a way how to apply about 40 um of PMMA on top of an 4"
wafer. I don't want to do multiple spincoating because of stress
problems. I need to avoid cracks in the structure as much as possible.

Thanks for any advises or tips to following topics:

1) Casting
- how to get such a thin layer uniform?
- stress problems?
- what kind of a "spacer" should I use? (Myler?)
- repeteability?

2) spincoating (one step or two)
- any experience in preparing the PMMA mixture in-house?
- preparation of the resist (molecular weight of the powder PMMA,
solvent, mixing..)
- spin speed, baking/relaxing times

3) Bonding
- what kind of bonding (using MMA or something else)
- way of machining afterwards
- stress problems?


Thanks a lot for your time

Regards

Josef Kouba