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Thanks Bob!<br>
<br>
A wonderful example of how "contamination" can be managed by means
other than the paranoia -- something we struggle with as we try to
serve a broader community while trying to keep our electronics and
detector researchers happy. I would hazard a guess that this works
in industry because distillation is vacuum rather than heated and
that an additional RCA-equivalent clean is used before high
temperature processing steps, thus minimizing the risk of driving in
mobile ions.<br>
<br>
That said, at Stanford, we do promote paranoia when it comes to
dedicated teflon cassettes in MOS stations because of their
propensity to absorb whatever chemical they are exposed to. I've
not seen any data that shows cross-contamination due to this, but
have seen the results of off-gassing on wafers stored or heated in
chemical bath cassettes. The risk of significant carryover of HF
into piranha may be very low, but might be worth considering
dedicated cassettes when using pyrex.<br>
<br>
Mary<br>
<br>
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<pre class="moz-signature" cols="72">--
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
Paul G. Allen Bldg 141, Mail Code 4070
Stanford, CA 94305
(650)723-9980
<a class="moz-txt-link-abbreviated" href="mailto:mtang@stanford.edu">mtang@stanford.edu</a>
<a class="moz-txt-link-freetext" href="http://snf.stanford.edu">http://snf.stanford.edu</a>
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<div class="moz-cite-prefix">On 4/28/2016 1:21 PM, Robert M.
HAMILTON wrote:<br>
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<div dir="ltr">Keith,
<div><br>
</div>
<div>I'll stick my neck out!
<div><br>
</div>
<div>The UC Berkeley NanoLab uses fused silica tanks with
encased heaters and ground-fault detection for our piranha
baths. I am guessing your suggestion of Pyrex or an
alternative borosilicate glass will raise the hackles of
some Labnetwork readers. And, I cannot claim experience with
the impact of borosilicate glasses, used for piranha cleans,
for MOS devices.
<div><br>
</div>
<div>However, I can point to a patent issued to Alameda
Instruments that made H2SO4 reclaim/reprocessing systems
for a number of major semiconductor manufacturers. I also
have known, since boyhood the research glassblower who
made their vacuum stills. The glass used was Pyrex or an
alternative Duran, which is Schott's equivalent. This
leads me to the conclusion H2SO4 from a pyrex still was
good enough for Intel, Pyrex is probably good enough for
you.</div>
<div><br>
</div>
<div>Having said this if there is accidental contamination
via HF your Pyrex will contribute alkali and your devices
will be DOA. We have seen HF contamination in our baths on
a few occasions.</div>
<div><br>
</div>
<div>For reference see: <a moz-do-not-send="true"
href="https://www.google.com/patents/US4980032">https://www.google.com/patents/US4980032</a></div>
<div><br>
</div>
<div>Bob Hamilton</div>
</div>
</div>
<div><br>
</div>
<div>PS Caveat emptor! Corning now uses the term Pyrex for a
broader number of glasses than their traditional 7740.</div>
</div>
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<div><br>
Robert Hamilton<br>
</div>
University of CA, Berkeley<br>
Marvell NanoLab Equipment Manager<br>
</div>
Rm 520 Sutardja Dai Hall, MC 1754<br>
</div>
Berkeley, CA 94720<br>
</div>
Phone 510-809-8618 (desk - preferred)<br>
</div>
Mobile 510-325-7557 (my personal mobile)<br>
</div>
E-mail preferred: <a moz-do-not-send="true"
href="mailto:bob@eecs.berkeley.edu"
target="_blank">bob@eecs.berkeley.edu</a><br>
<a moz-do-not-send="true"
href="http://nanolab.berkeley.edu/"
target="_blank">http://nanolab.berkeley.edu/</a></div>
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<div class="gmail_quote">On Thu, Apr 28, 2016 at 10:59 AM, Keith
Franklin <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:keithf@ualberta.ca" target="_blank">keithf@ualberta.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Good day all,
<div><br>
</div>
<div>We're currently revisiting what vessels or tanks we
use for processing with hot piranha. Our most common
application is for cleaning a partially filled cassette
of 4" Si wafers. We typically purchase Pyrex 6944
vessel and have our glass shop cut them down to a more
reasonable height. In our last purchase cycle, we
noticed that the ID has changed ever so slightly and
it's now challenging to squeeze our standard Entegris
cassette into this vessel. We're currently looking into
custom machined PVC, PP, Teflon & Quartzware, as
well as off the shelf small volume tanks, etc.</div>
<div><br>
</div>
<div>I'm hoping to better understand what other similar
labs are using for this application (& potentially
6" wafers as well). Any advice or feedback would be
greatly appreciated.</div>
<div><br>
</div>
<div>Kind Regards,</div>
<div>Keith</div>
<div>
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