Hi,
I am experimenting an adhesion problem using SU8 3050 on a small Si substrate (7mm x 7mm). Specifically, this is my current recipe:
- Substrate preparation
Wash with Acetone -> IPA -> DI Water (ultrasonic bath for 5 min)
Dry with nitrogen
Bake for 2min @ 90°
- Spinning
Resist: SU8 3050
30s @ 1500 rpm
n.b. after this step the SU8 is perfectly spinned (apart from classic coffee ring at the edge) but the surface looks perfectly fine
- Soft Bake
3min @ 65°
30 min @ 90°
3 min @ 65°
After this step SU8 shrinked. Some parts of the carrier are without any coating. I would say that the 40% of the surface has no SU8 (probably evaporated).
It is crazy because I have used the same receipe with a larger silicon carrier (20mm x 20mm) and everything is fine after the soft baking.
Do you have any idea about I could avoid this effect? And how would you explain this effect?
I tryed to modify rpm and/or baking time but I did not got much more better results... Do you think O2 ash before spinning could help ?
Thanks !
A dry with O2 is intersting and resolved the problem of adhesion.
The O2 air is necessary to form a SiO2 thin layer. This layer is hydrophilic leading the formation of thin layer by Spin coating.
It's necessary to read and quote this article :
M.-B. Bouzourâa, Y. Battie, S. Dalmasso, M.-A. Zaïbi, M. Oueslati, A. En Naciri, Superlattices and Microstructures 104 ( 2017) 24–36.
Hello Valerio,
My suggestion would be to perform a proper dehydration bake prior to spinning, say 200 oC for 10-20 minutes. Allow substrate to cool to RT before spincoating.
Otherwise treatment with O2 plasma or UV-Ozone should help to activate the surface.
Jules:
Hi Jules,
Thank you very much for your reply and for your help !!
I'll give a try with your suggestions !!
Valerio
Hi Bouzourâa,
Thank you very much for your time. It seems that both you and Jules agree that the O2 plasma could help: I will try this method and I will post here my results !!
I will also read your paper and quote when necessary! Thank you again
Valerio
I confirm that O2 plasma helps avoiding this problem. I tried with 2min @ 120W and the results are visibly better: the SU-8 coating did not srink after soft baking for 1h @ 95°C on a 7mm x 7mm Si slice. Thank you very much for your help!
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films