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Ian:<br>
<br>
While you will likely get more thorough responses from others on
this matter, let me share some or our experiences in this area. In
particular, these tools generate a lot of polymer. The same
chemistry that you are relying on generating the polymer on your
wafers during half of the switched etch/deposition process is also
going to produce a low-grade polymer everywhere else. Much of the
polymer that you find in the foreline tends to be rather gummy and
difficult to remove ... at least that is our experience. Many (but
not all) machines have heated turbo pumps and I believe that had
been found to be pretty effective in terms of minimizing polymer
build up in one of your most expensive components on these tools.
One of our machines has a water cooled trap between the heated turbo
and the remainder of the foreline ... but, to be honest, that trap
has not proven to be particularly effective in our case.<br>
<br>
Because the forelines tend to get pretty well coated with a sticky,
gummy polymer, we have found them to be pretty difficult to clean.
One "trick" that seems to work pretty well in the case of the
forelines is to very carefully pour some liquid nitrogen down the
foreline which will freeze it and cause it to fall off in chunks.
This, of course, has to be done VERY carefully due to the hazards of
working with liquid nitrogen including worrying about "burns" due to
the extreme cold and asphyxiation due to displacement of oxygen in
the air. One thing that we haven't tried, but may be easier than
dealing with liquid nitrogen is to see whether packing a length of
foreline in dry ice may have the same effect ... dry ice has it's
own problems because of it's very low temperature and sublimation of
something that can displace oxygen, but it is probably easier to
handle than liquid nitrogen.<br>
<br>
While the polymer itself isn't wildly toxic or flammable in the way
that some of your pumps and forelines on other deposition tools are
(things that pump silane and DCS, for example) we treat all
forelines very carefully and, in particular, for anything that is
the least bit "powdery or dusty" make sure that we have adequate
protection to avoid inhaling or ingesting anything coming from these
pump lines.<br>
<br>
Finally, depending on the distance your foreline pump lives from the
main tool, you may need to consider upsizing the diameter of your
foreline a bit to help offset the constriction that will take place
as your get polymer build up between periodic cleaning.<br>
<br>
Good luck,<br>
<br>
John<br>
<br>
<br>
On 11/4/2013 3:36 PM, Ian Harvey wrote:
<blockquote
cite="mid:18E314D3-69D5-40ED-A66F-F5BF84C8756A@eng.utah.edu"
type="cite">
<div>Dear Labnetwork colleagues,</div>
<div><br>
</div>
<div>We are installing a used STS DRIE tool acquired from the used
tool market and used for Bosch-Si etch. </div>
<div><br>
</div>
<div>We are unsettled by the large amount of white powder
collected in the foreline and inside the large turbopump. The
turbo is becoming unbalanced as flakes come off, and we are
getting ready to trade in the large maglev pump for a refurb,
and clean the forelines.</div>
<div><br>
</div>
<div>Does anyone have experience with what the powder is (F-C-S-O
/ EDS analysis attached), its risks, and how to safely manage it
during pump removal, packing and declaration for shipping?</div>
<div><br>
</div>
<div>Thanks!</div>
<div><br>
</div>
<div>Ian</div>
<div><br>
</div>
<div apple-content-edited="true">
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<div style="word-wrap: break-word;"><span
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<div style="word-wrap: break-word;"><span
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Ian R. Harvey, Ph.D.<br>
</div>
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Nanofab </div>
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<div>Micron Microscopy Core</div>
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<br>
</div>
<div>801/585-6162 (voicemail)<br>
801/581-5676 (lab main number)<br>
<a moz-do-not-send="true"
href="http://www.nanofab.utah.edu">www.nanofab.utah.edu</a></div>
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</blockquote>
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