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<p class="MsoNormal"><span style="color:#1F497D">Some great info on this thread.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> I have nothing to add to Tom Tribble’s input except a sincere thank you for supplying me with a non- interruptive, constant N2 source.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="color:#1F497D">As a sort of side note, I would like to mention a way to save some N2 in wet process tools. Certain brands of SRD’s, SST’s and SAT’s are specified to have a nitrogen connection to an
“insurance” venturi. This venturi keeps the bowl seal under a negative pressure for when it fails in an effort to control particle distribution of the seal material. Some brands have a separate connection and others are fed from a common point. The units with
a separate connection can be fed with CDA and others that are connected commonly will require some modification to split off the venturi feed from the rest of the n2 purge, dry, etc. Doing so can save an average of 1-2 LPM constant flow which can, and will
add up.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="color:#1F497D">Steve Paolini<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="color:#1F497D">Equipment Dood<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="color:#1F497D">Harvard University Center for Nanoscale Systems<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> labnetwork-bounces@mtl.mit.edu [mailto:labnetwork-bounces@mtl.mit.edu]
<b>On Behalf Of </b>Morrison, Richard H., Jr.<br>
<b>Sent:</b> Friday, March 27, 2015 2:08 PM<br>
<b>To:</b> John Shott; labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] LN2 vs N2 generation on site<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Hi Everyone,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I would like to share with you some details. We have 2 3000 gallon tanks. Tank one feeds the Microfabrication Laboratory and is filled every other day. The 2<sup>nd</sup> tank feeds 3 different labs, Assembly,
MCM and 5<sup>th</sup> Floor and is filled every 4<sup>th</sup> day, this systems is all SS from the tank to point if use. We do not use purifiers so I expect that even though the LN2 is 99.999% I have something less at the point of use.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The Microfab is mostly dry boxes, N2 guns, purge for pumps, purge for 3 furnace tubes (oxidation) and 3 LPCVD system, poly, nitride and SiC. We run all dry pumps and have not had any problems using this gas stream.
We shut of the SRD at night and weekend to save gas but I am still at a high flow. From the tank to the Microfab loop is all SS, the Microfab loop is oxygen free EP Copper silver soldered.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Microfab runs 23 cuft to 34cuft/min (SRD dependant)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">MCM runs 3-6 cuft/min depending on tools usage<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Assembly 1-16 cuft/min depending on tool usage<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">5<sup>th</sup> Floor 1-5 cuft/min depending on tool usage<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The MCM, Assembly and 5<sup>th</sup> floor need oxygen free Nitrogen with no moisture; so my guess here 99.99% Nitrogen or 99.9%?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The Microfabrication should be 99.99% or does it need 99.999%. We have never had our existing system analyzed, any ideas here?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><img width="482" height="289" id="Chart_x0020_7" src="cid:image001.png@01D068A9.1C7D9BA0"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><img width="482" height="289" id="Chart_x0020_8" src="cid:image002.png@01D068A9.1C7D9BA0"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks for your comments so far and I looked forward to more discussion. BTW after fees and surcharges I pay $1.23 per 100cuft and I use 1.45million cuft per month (data from flow meters). The company delivers
the equivalent of 2.6million cuft so I lose to evaporation and cooling 1million cuft per month, does this sound right or do I have a big leak some place?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Rick<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> John Shott [<a href="mailto:shott@stanford.edu">mailto:shott@stanford.edu</a>]
<br>
<b>Sent:</b> Friday, March 27, 2015 11:55 AM<br>
<b>To:</b> Tribble, Thomas; Morrison, Richard H., Jr.; <a href="mailto:labnetwork@mtl.mit.edu">
labnetwork@mtl.mit.edu</a>; Nibarger, John<br>
<b>Subject:</b> Re: [labnetwork] LN2 vs N2 generation on site<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Rick: <br>
<br>
This is an excellent question and I thank Tom Tribble and John Nibarger for their initial contributions to this topic ... and others that will undoubtedly soon follow.<br>
<br>
First, let me get my remedial class question out of the way: Tom, you've got me feeling like a rank beginner. I must confess to being unfamiliar with the 1<span style="color:#1F497D">δ, 3δ, and 6δ notation for gas purity. Is this the equivalent of what I
know as dot notation? In other words, so they correspond to 1-, 3-, and 6-nines purity that is 1.0, 3.0, and 6.0 in dot notation? Where 99.5% purity is 2.5?</span> Or is
<span style="color:#1F497D">δ notation something different?</span><br>
<br>
I would like to add confirmation of your "unofficial audit" that found that 10% of your usage demands high purity.<br>
We also have a 9000 gallon LN2 tank (which, sadly, gets filled every fourth day). We have two sets of vaporizers on it: the big set supplies the copper-piped "house N2" and the smaller vaporizers that also go through a switchable set of purifiers and then
feed our stainless-piped "UHP N2" system. Nouse N2 usage is dominated by pump purge. We have totalizing flow meters on each main line and typically observe that the UHP N2 consumption is 130-200 SLM and the house N2 consumption is 2500-2800 SLM. In other
words our total nitrogen flow is very close to 3000 SLM (or about 4.5M - 5.0M SCF per month!). In other words, our high-purity consumption is in the range of 5-7% of our total consumption. Note: we actually use the house nitrogen for our SRDs ... if we moved
that intermittent high-flow to UHP N2, it probably gets us close to, but no higher than, 10%.<br>
<br>
My question to the labnetwork community is what level of nitrogen purity would you want for pump purges of some of our nastier processes? For example, things like DCS and ammonia for LPCVD nitride? Hydrogen, germane, silane, plus dopants for an epitaxial
process? is 1.0 nitrogen good enough? The way that I look at it, that is only a 50% reduction of oxygen as compared to what you find in air. How about 2.0 nitrogen (99%), good enough?<br>
<br>
And one question to John Nibarger: is the moisture content of your generated nitrogen controlled by the moisture content of your feed CDA? In other words, with your incoming CDA dew point of -40C is the dew point of your generated nitrogen also approximately
-40C? If the incoming CDA were drier (say -55C to -60C) do you expect that your generated nitrogen would also be that much drier? I ask because for pumps running corrosives such as HCl, Cl2, BCl3, and HBr it would seem that dryness of the purge gas would
be more important than the background oxygen content.<br>
<br>
Thank you all,<br>
<br>
John<o:p></o:p></p>
<div>
<p class="MsoNormal">On 3/24/2015 1:31 PM, Tribble, Thomas wrote:<o:p></o:p></p>
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<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:#1F497D">Richard,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">We haven’t switched to onsite generation for the fab, but we (Harvard) have looked at it. The Harvard fab has a 9000 gallon LN2- 3δ storage that gets re-filled approximately once a week. The storage facility
occupies approximately 300 GSF, and there is no more real estate available for this purpose. Based upon a much smaller on-site generator recently completed, on-site generation to replace the fab storage facility would require more real estate than is available.
Part of the demand for space is the self-imposed requirement for N+1 redundancy. This also affects the capital budget.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">But if saving money is your focus, I suggest that your discussion should be focused on the purity of your gas requirements. Locally generated 1δ gas is
<s>inexpensive</s> cheap to produce. Locally generated 3δ gas is moderately expensive to produce. Locally generated 6δ gas is
<b>very</b> expensive to produce. From the refinery, 3δ gas is all that is produced and transported. What we at Harvard use is 6δ gas (3δ gas run through a purifier). An unofficial audit has shown that less than 10% of our usage actually demands 6δ purity.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Want to save money? Figure out your demand by purity and segregate the flows (piping). Provide your pump and gas cabinet purges with on-site generated 1δ gas. Your facility will save.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Tom Tribble</span><o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a> [<a href="mailto:labnetwork-bounces@mtl.mit.edu">mailto:labnetwork-bounces@mtl.mit.edu</a>]
<b>On Behalf Of </b>Morrison, Richard H., Jr.<br>
<b>Sent:</b> Tuesday, March 24, 2015 12:04 PM<br>
<b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> [labnetwork] LN2 vs N2 generation on site</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Hi everyone,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I am paying >$220K per year for LN2 to generate Nitrogen for my fab. Have any of you guys switched to onsite Nitrogen generator?
<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Looking for ideas on:<o:p></o:p></p>
<p class="MsoNormal" style="text-indent:.5in">Cost of system<o:p></o:p></p>
<p class="MsoNormal" style="text-indent:.5in">Maintenance cost of system <o:p></o:p></p>
<p class="MsoNormal" style="text-indent:.5in"> Quality of the Nitrogen.<o:p></o:p></p>
<p class="MsoNormal" style="text-indent:.5in">Operating cost per CuFt of Nitrogen<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Rick<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Draper Laboratory<o:p></o:p></p>
<p class="MsoNormal">Principal Member of the Technical Staff<o:p></o:p></p>
<p class="MsoNormal">Group Leader Microfabrication Operations<o:p></o:p></p>
<p class="MsoNormal">555 Technology Square<o:p></o:p></p>
<p class="MsoNormal">Cambridge Ma, 02139-3563<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><a href="http://www.draper.com">www.draper.com</a><o:p></o:p></p>
<p class="MsoNormal"><a href="mailto:rmorrison@draper.com">rmorrison@draper.com</a><o:p></o:p></p>
<p class="MsoNormal">W 617-258-3420<o:p></o:p></p>
<p class="MsoNormal">C 508-930-3461<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
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