I have always etched Si to create masters for PDMS molding and the etch depth never went beyond 200 um. Now, I need to create structures with a high of 450-500 um and the smallest feature size is 30 um. I don't know what is the best way to fabricate these masters. I don't have experience with thick SU-8 structures, but I assume it wouldn't easy as well. Any insight is appreciated!
Thank you Iiro Kiiski and Yang Liu
!So, SU-8 is the one worth the try. Do you think SU-8 2050 would be the right choice?
Also, I was wondering how double coating process is carried out because since the polymer is not polymerized during the soft bake, adding the second layer that contains a solvent might distract and fluidize the first layer. And the development would be very tricky I assume.
Have you checked out DRIE?
https://en.wikipedia.org/wiki/Deep_reactive-ion_etching
Hi Craig Galligan , that's what I've always done. However, I am not sure if I could get perfect straight sidewalls when etching 500 um.
Hi Hanie Kavand, it's actually pretty challenging to reach this high aspect ratio :) I would suggest using the Su-8 2150 that allows for higher thickness and try to set the spin-coating parameters in order to directly reach a thicker layer. Otherwise i would also recomment to try with the two-layers technique!
Hi Alice Massimiani , thanks! Right. the max aspect ratio with SU-8 should be 10-5. Can you please tell me how does the two-layer technique work?
For someone who passes by here:
I have found SUEX, a dry film resist, that seems to be developed for such applications. Seems interesting, but I haven't tried it out yet.
https://djmicrolaminates.com/suex/
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