[labnetwork] Using CDA, rather than N2, as pump purge in Bosch-like processes?

[Vito Logiudice]

Hi John,

I have in the past used CDA fed through a cascade of nitrogen membrane
filters to achieve 99.9% N2 purity which was then used to purge dry pumps
used in a variety of applications. The setup worked well without any
issues for a number of years. I don't recall the membrane manufacturer we
used at the time but a quick Google search will reveal a few current
vendors. Here's some info I came across on Air Liquide's site:
http://www.medal.airliquide.com/en/nitrogen-membranes/medal-nitrogen-membra
ne-modules.html

As several others have already mentioned, the CDA supply must be monitored
to ensure it remains oil-free & dry. In my particular application, the
compressor/dryer was dedicated to fab operations under my responsibility
and therefore easily monitored.

Best regards,
Vito
-- 
Vito Logiudice  M.A.Sc., P.Eng.
Director of Operations, Quantum NanoFab
University of Waterloo
200 University Avenue West
Waterloo, ON      Canada   N2L 3G1
Tel:  1-519-888-4567  ext. 38703
Email: vlogiudi at uwaterloo.ca
Website: https://qncfab.uwaterloo.ca/







-----Original Message-----
From: John Shott <shott at stanford.edu>
Date: Thursday, 11 April, 2013 11:47 AM
To: Labnetwork <labnetwork at mtl.mit.edu>
Subject: [labnetwork] Using CDA, rather than N2,	as pump purge in
Bosch-like processes?

>Labnetwork Community:
>
>Like many of you, I suspect, nitrogen is the single largest non-salary
>expense associated with running our facility.
>
>Much of our nitrogen is used for pump purges in dry pumps.  Our average
>dry pump seems to use about 1 CFM (sorry, 25-30 SLM ...) which, at our
>pricing is about $4k per year.  For virtually all deposition processes
>using reactive gases and etch processes using corrosive gases, using
>nitrogen as a pump purge seems to be a firm requirement.  It is not as
>obvious, to me at least, that nitrogen is required in something like a
>SF6/fluorocarbon-based etch process like the switched Bosch processes
>that many of us run.  While I know that CDA isn't "free", in our case,
>the LN2 bill definitely comes out of our pocket whereas as CDA is a
>University supplied and supported building utility.
>
>What experience, recommendations, or cautions can you offer related to
>switching our Bosch process tools from nitrogen to CDA pump purges?  If
>it matters, the dew point of our CDA is believed to be less than -40 C,
>but is not monitored continuously (and maybe not even monitored
>periodically ...).
>
>Thanks for your consideration,
>
>John
>
>
>
>
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