Etching with SU-8 on the wafers

kristina_lamers at kristina_lamers at
Thu Jul 14 22:55:05 PDT 2005


I'm in the ME342 class, and am working on a microfluidic device that has SU-8 on it.
I wanted to check into the possibility of running wafers with SU-8 on
them in the STS and WBMetal. My team was
originally trying to make structures out of SU-8. We have not had much
success as we can't get the SU-8 layers to bond together well and the
thick SU-8 comes out very uneven due to lack of level of the
hotplates. I tried creating our main structure out of Si in the STS,
which worked well, but we haven't been able to get a layer of SU-8 to
bond to Si and we need that layer to seal our microfluidic devices.
Therefore I would like to try putting SU-8 on the backside of a wafer
as the etchstop and then using SPR 220 to pattern the wafer for
through etch. I could also put another Si wafer on the back as a

We have a similar issue for wet etching. We are creating Al heaters on top of cured SU-8, 
and would like to etch them in WBMetal. 

SU-8 is an epoxy based resist that it hard to remove once it is cured. We are planning to use cured SU-8 in these steps, so there shouldn't be any problems with SU-8 dissolving in the wet etch or even in the plasma etch. The only plasma etch reported to take off cured SU-8 is CF4, which is not part of the STS process, and even then it etches slowly. More information on SU-8 can be found at

Can you tell me whether you would allow us to try these steps, or
what other information you might need to make a decision? If it's helpful to prioritize, we can still do the wet etch in WBGeneral, but we don't have another place to do the deep Si etch. We are on a very short timeline for the class, and would therefore greatly appreciate this issue being addressed quickly.

Thanks for your consideration,

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