[mems-talk] Dimples in SU-8 film

[Gareth Jenkins]

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?
>  
>