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Milan:<br>
<br>
You will likely get a wide range of opinions on this issue.
However, a lot will depend on the quality of the gas that is coming
out of your system. Telling you what I have may be irrelevant if
your gas is either much better or much worse than what we have.<br>
<br>
We (the Stanford Nanofabrication Facility) have a single, stainless
steel 9000 gallon LN2 tank that supplies both our copper-piped house
nitrogen system and our stainless-routed UHP nitrogen system. Aside
from the piping, the other thing that differentiates our UHP system
from our house nitrogen system is a set of A/B switchable Entegris
10M purifiers and more particle filtration.<br>
<br>
At the moment, we have no real-time monitoring of either system ...
but we are just about to add real-time moisture monitoring to both
our house nitrogen and UHP nitrogen in the form of Michell Pura OL
hygrometers to be able to measure moisture content in real time on
these systems. While there are clearly other possible impurities in
your nitrogen, I believe that moisture is both the most problematic
and the easiest to measure.<br>
<br>
As far as spot check measurements, that last time that we had our
house nitrogen, UHP nitrogen, and argon systems measured (and we
measured each both close to the tank and in the clean room near the
end of the distribution lines) we observed the readings that I've
reproduced in the following table. Note: our last spot check
occurred nearly a year ago (11/19/2013). We measured 3 gas systems
(house nitrogen, UHP nitrogen and argon both near the tank and in
the clean room. We measured oxygen, water vapor, total hydrocarbon,
and particles per cubic feet (> 0.1 um).<br>
Note: if this table gets trashed in email translation, I'll find a
way to post it on line.<br>
<br>
Our most recent measurements were:<br>
<br>
<table style="border-collapse: collapse;width:371pt" border="0"
cellpadding="0" cellspacing="0" width="494">
<colgroup><col
style="mso-width-source:userset;mso-width-alt:3949;width:81pt"
width="108"> <col
style="mso-width-source:userset;mso-width-alt:3072;width:63pt"
width="84"> <col
style="mso-width-source:userset;mso-width-alt:3510;width:72pt"
width="96"> <col
style="mso-width-source:userset;mso-width-alt:2706;width:56pt"
width="74"> <col
style="mso-width-source:userset;mso-width-alt:2633;width:54pt"
width="72"> <col
style="mso-width-source:userset;mso-width-alt:2194;width:45pt"
width="60"> </colgroup><tbody>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;width:81pt" height="20"
width="108">Gas</td>
<td class="xl63" style="border-left:none;width:63pt"
width="84">Location</td>
<td class="xl63" style="border-left:none;width:72pt"
width="96">Oxygen (ppm)</td>
<td class="xl63" style="border-left:none;width:56pt"
width="74">H2O (ppm)</td>
<td class="xl63" style="border-left:none;width:54pt"
width="72">THC (ppm)</td>
<td class="xl63" style="border-left:none;width:45pt"
width="60">Particles</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">House Nitrogen</td>
<td class="xl63" style="border-top:none;border-left:none">Tank</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.58</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.5</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">56</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">House Nitrogen<span style="mso-spacerun:yes"> </span></td>
<td class="xl63" style="border-top:none;border-left:none">Clean
room</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.6</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.55</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">80</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">UHP Nitrogen</td>
<td class="xl63" style="border-top:none;border-left:none">Post
Purifier</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.028</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.09</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">UHP Nitrogen</td>
<td class="xl63" style="border-top:none;border-left:none">Clean
room</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.038</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.098</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">10</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">Argon</td>
<td class="xl63" style="border-top:none;border-left:none">Tank</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.026</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.54</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">14</td>
</tr>
<tr style="height:15.0pt" height="20">
<td class="xl63" style="height:15.0pt;border-top:none"
height="20">Argon</td>
<td class="xl63" style="border-top:none;border-left:none">Clean
room</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.068</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">0.55</td>
<td class="xl63" style="border-top:none;border-left:none"><
0.01</td>
<td class="xl63" style="border-top:none;border-left:none"
align="right">11</td>
</tr>
</tbody>
</table>
<br>
<br>
While our UHP nitrogen (which comes from the same tank as our house
nitrogen but goes through purifiers) is better than our house
nitrogen, our house nitrogen is pretty good as well: less than 1
ppm oxygen and water vapor and a reasonable number of particles ...
particularly if it is venting a particle-laden process like
sputtering or ebeam evaporation. Of course, people tend to be more
cavalier about using "PolyFlo" tubing on a house nitrogen system
which can be an additional source of moisture at least locally.
Even if that is done, if it is downstream of a regulator, you
probably won't significantly increase moisture levels in other parts
of your distribution system.<br>
<br>
As a side note, we run house nitrogen from copper lines to our SRDs
(spin-rinse dryers) because of the high flow requirements ... that
may well cause your clean room contractor a bit of an apoplectic
fit.<br>
<br>
Of course, you would likely want to at least spot check the quality
of your house and UHP nitrogen to see if they are comparable to
ours.<br>
<br>
Finally, most things that get vented, get opened to atmosphere at
some point. Air at 20% oxygen content and 45% RH can undo your very
careful UHP venting in a matter of milliseconds ...<br>
<br>
Good luck,<br>
<br>
John<br>
<br>
<div class="moz-cite-prefix">On 10/31/2014 9:15 AM, Milan
Begliarbekov wrote:<br>
</div>
<blockquote
cite="mid:7EB621C923665D458D0ED5D9E722D7210C3C6070@EXPM5704.enterpriseapps.cuny.adlan"
type="cite">
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<div style="direction: ltr;font-family: Tahoma;color:
#000000;font-size: 10pt;">Hi All,
<div><br>
</div>
<div>At the moment we're trying to decide the purity / source of
the nitrogen we will use to vent our tools. The building has a
bulk nitrogen system that is plumbed to the clean room in
copper pipes. Our clean room contractor believes that that
nitrogen might be too dirty to use as a vent gas and
recommends ultra pure nitrogen. I am wondering if anyone has
thoughts on this matter. I believe that it is possible to get
99.998 % N2 out of copper pipes. Is that the case? If not are
there purifiers / dryers that are commonly used? This is only
a vent gas and not a process gas. </div>
<div><br>
</div>
<div>Any wisdom in this matter will be highly appreciated.</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>milan</div>
<div>Technical Cleanroom Manager</div>
<div>CUNY Advanced Science Research Center</div>
<div><a class="moz-txt-link-abbreviated" href="mailto:Milan.Begliarbekov@asrc.cuny.edu">Milan.Begliarbekov@asrc.cuny.edu</a></div>
</div>
<br>
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