[labnetwork] KOH/IPA Solution

[Bill Flounders]

Michael,
Your local authority having jurisdiction (AHJ) will define if you are
allowed to drain dispose modest volumes of water miscible solvent
- just as we all dispose limited volumes of ethanol and rubbing alcohol
from our homes. I find your proposal that most of the solvent has 
evaporated
as part  of the process an additional compelling reason for approval.

As a separate topic, I offer that we also run a KOH bath and
we intentionally sparge the tank with O2 to minimize hillock
formation as O2 saturated solutions provide O2 to rapidly react
with H2 produced at the  surface during etching. H2 bubbles cause 
micromasking
which results in micropyramid (or hillock) structures. Some related refs:
J. Micmmech. Microeng. 5 (1995) 209-218.
J. Micromech. Microeng. 9 (1999) 139--145.

I welcome separate off line contact if you want to discuss further.
Bill Flounders
UC Berkeley NanoLab


Michael Khbeis wrote:
> Good Morning,
>
> We have just replaced all of our wet processing stations and are 
> setting up a 6L recirculating bath of KOH w/ ~20% IPA as a surfactant. 
>  I am presuming that the IPA will readily evaporate and will not pose 
> a regulatory issue with dumping to waste water treatment.  I was 
> wondering if most of you still use IPA or have moved to other 
> surfactants for Si preferential wet etch.  If you still use IPA how do 
> you handle the effluent?
>
> I appreciate the fab knowledge support community that you all 
> contribute to.
>
> Gratefully,
>
> Dr. Michael Khbeis
> Associate Director
> Microfabrication Facility (MFF)
> University of Washington
> Fluke Hall, Box 352143
> (O) 206.543.5101
> (C) 443.254.5192
> khbeis at uw.edu <mailto:khbeis at uw.edu>
>
>
>
>
> _______________________________________________
> labnetwork mailing list
> labnetwork at mtl.mit.edu
> https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20120622/b89073c4/attachment.html>