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Dear Pradeep and all,
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<div class="">Here are some thoughts and experiences:</div>
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<div class="">At Utah we made the conscious decision to move to dry pumps and not allow any wet pumps into the facility as we moved into our new nanofab. We cleaned and PM'ed every tool that was previously on wet pumps, and used all new downstream hardware.</div>
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<div class="">This decision was based on:</div>
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<div class="">1) the observation of pump oil saturating the downstream exhaust system and mixing with hazardous reaction products to create dripping toxic cocktails. This greatly complicates any modifications to the exhaust line, places trade workers at risk
during modification or demolition, and places the exhaust system itself under corrosive liquid attack.</div>
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<div class="">2) Not concerned for back pressure events contaminating chambers but instead concerned for the steady state back diffusion of volatile oils into the deposition chamber. This is something an anti-suckback valve will not help, nor will other schemes
such as molecular sieves (after a short period). I would be very interested in any data that peers have to validate empirical observation of delaminating or non-adhering thin films onto oil contaminated surfaces.</div>
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<div class="">3) The contamination of the lab itself from the leaky pumps. Each pump sits in a drip tray and the volatile oils soon coat every lab surface, creating slippery floors and loading the HEPA filters. Some individuals are sensitive to the effects
of prolonged breathing of these vapors in what is otherwise considered a clean-for-breathing airspace. </div>
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<div class="">4) Once a lab is contaminated with pump oil it is very difficult and expensive to revert back.</div>
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<div class="">I have also seen failed oil-sealed pumps backstreaming oil up into the nitrogen ballast line, so that the needle valve, bb-style N2 rotameter was bubbling in oil. This resulted in back contamination of the "ultra-pure" nitrogen line.</div>
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<div class="">I shudder to think of a decision to revert from dry back to wet pumps with all the ramifications such a decision entails.</div>
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<div class="">—Ian Harvey</div>
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<div>Ian R. Harvey<br class="">
PRISM Cleanroom Director<br class="">
Princeton University<br class="">
70 Prospect Avenue, Princeton, NJ 08540<br class="">
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<div>609-258-5922 (office)</div>
<div>609-285-9951 (cell)</div>
<div><a href="mailto:iharvey@princeton.edu" class="">iharvey@princeton.edu</a></div>
<div class=""><a href="http://PRISM-Cleanroom.princeton.edu" class="">PRISM-Cleanroom.princeton.edu</a></div>
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<div class="">Begin forwarded message:</div>
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<div class="" style="margin: 0px;"><span class="" style="font-size: inherit;"><b class="">From: </b></span><span class="" style="font-size: inherit;">Pradeep Nyaupane <<a href="mailto:nyaupanepradeep@gmail.com" class="">nyaupanepradeep@gmail.com</a>></span></div>
<div class="" style="margin: 0px;"><span class="" style="font-size: inherit;"><b class="">Subject: </b></span><span class="" style="font-size: inherit;"><b class="">[labnetwork] Backing Vacuum Pump - Dry pumps vs Oil Pumps</b><br class="">
</span></div>
<div class="" style="margin: 0px;"><span class="" style="font-size: inherit;"><b class="">Date: </b></span><span class="" style="font-size: inherit;">November 3, 2019 8:21:06 AM EST<br class="">
</span></div>
<div class="" style="margin: 0px;"><span class="" style="font-size: inherit;"><b class="">To: </b></span><span class="" style="font-size: inherit;">"<a href="mailto:labnetwork@mtl.mit.edu" class="">labnetwork@mtl.mit.edu</a>" <<a href="mailto:labnetwork@mtl.mit.edu" class="">labnetwork@mtl.mit.edu</a>><br class="">
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<div class="">Dear All,</div>
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<div class=""> We have been using Dry pumps for turbo pump backing for Sputters, E-beam evaporators. And are planning to swap to oil pump with an anti-suck back valve, whenever required (in case dry pumps go bad).</div>
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<div class="">We would like to know whether any of you are using oil pumps are being used as backing pump for Turbo / Cryo / DP.<br class="">
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<div class="">Any advice / suggestions would be greatly appreciated.</div>
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<div class="">Thank You in advance.</div>
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<span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">Thanks & Regards,</span><br class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255);">
<span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">Pradeep Nyaupane</span><br class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255);">
<br class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255);">
<span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">Technical Superintendent,</span></div>
<div dir="ltr" class="">Equipment Maintenance Team In-charge, </div>
<div dir="ltr" class="">IITBNF, <span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">Electrical Engg Dept </span></div>
<div dir="ltr" class=""><span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">IIT Bombay, India</span></div>
<div dir="ltr" class=""><span class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255); float: none; display: inline;">Tel No. 02225764471(O)</span><br class="" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; background-color: rgb(255, 255, 255);">
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