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Michael,<br>
Your local authority having jurisdiction (AHJ) will define if you
are <br>
allowed to drain dispose modest volumes of water miscible solvent <br>
- just as we all dispose limited volumes of ethanol and rubbing
alcohol <br>
from our homes. I find your proposal that most of the solvent has
evaporated <br>
as part of the process an additional compelling reason for
approval.<br>
<br>
As a separate topic, I offer that we also run a KOH bath and <br>
we intentionally sparge the tank with O2 to minimize hillock<br>
formation as O2 saturated solutions provide O2 to rapidly react <br>
with H2 produced at the surface during etching. H2 bubbles cause
micromasking<br>
which results in micropyramid (or hillock) structures. Some related
refs:<br>
J. Micmmech. Microeng. 5 (1995) 209-218.<br>
J. Micromech. Microeng. 9 (1999) 139–145.<br>
<br>
I welcome separate off line contact if you want to discuss further.<br>
Bill Flounders<br>
UC Berkeley NanoLab<br>
<br>
<br>
<div class="moz-cite-prefix">Michael Khbeis wrote:<br>
</div>
<blockquote cite="mid:F95D95E3-1C99-44DF-8268-930B7FD5DE75@uw.edu"
type="cite">Good Morning,
<div><br>
</div>
<div>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?</div>
<div><br>
</div>
<div>I appreciate the fab knowledge support community that you all
contribute to. </div>
<div><br>
</div>
<div>Gratefully,</div>
<div> <br>
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<div style="word-wrap: break-word;
-webkit-nbsp-mode: space; -webkit-line-break:
after-white-space; ">Dr. Michael Khbeis<br>
Associate Director<br>
Microfabrication Facility (MFF)<br>
University of Washington</div>
<div style="word-wrap: break-word;
-webkit-nbsp-mode: space; -webkit-line-break:
after-white-space; ">Fluke Hall, Box 352143<br>
(O) 206.543.5101<br>
(C) 443.254.5192<br>
<a moz-do-not-send="true"
href="mailto:khbeis@uw.edu">khbeis@uw.edu</a><br>
<br>
<br>
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