120C for 2mins may not be enough to fully dehydrate your wafer. I would
recommend 220C for at least 30mins.
Also, how are you cleaning the wafer prior to dehydration? I have
experienced dimples due to a contaminated H2SO4 cleaning solution.
Yue Mun Pun, Jeffrey wrote:
> Hi,
> I am trying to coat 2-3 layers of SU-8 2050. My process is aas follows:
>
> 1. Dehydration bake SiO2 wfr at 120'C for 2mins
> 2. Spin coat SU-8 2050 at 500rpm and ramp up to 3000rpm for 30sec.
> 3. Soft bake the first layer at 65'C for 3mins (ramped from 50'C to 65'C and
hold for 3mins)
> 4. Return wafer to spin coat another layer at the same conditions stated in
2.
> 5. Soft bake wafer at 65'C for 5mins and ramp to 95'C for 20mins, since the
layers now have a nominal thickness of 100 microns.
>
> I noticed that while baking at 95'C the SU-8 film developed dimples. These
may or may not be an issue for my process, but they are cosmetically ugly. Can
anyone tell me how do I solve this dimple issue?
>
>