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

[Fouad Karouta]

Hi John,

It is true N2 for purging dry pumps can be a very pricy item. I don't
believe CDA is an option especially with a PECVD tool when using SiH4 for
instance.

An idea for discussion:
I believe the pumps do require a really low amount of N2 when in standby
(about 1 SLM) while the 25-30SLM should be used (required) during processes
and I am investigating with equipment manufacturers to add a feature to the
software controlling the total system which would increase N2 flow when
starting a process and maintain it like 10-15 min after process end and
switch back to standby mode. Most dry pumps controls allow such a feature
but manufacturers are not implementing it among their options and if all of
us would push in that direction I am convinced we can reach there. 

Kind regards, Fouad

*********************************
Facility Manager ANFF ACT Node
Research School of Physics and Engineering
Australian National University
ACT 0200, Canberra, Australia
Tel: + 61 2 6125 7174
Mob: + 61 451 046 412
Email: fouad.karouta at anu.edu.au

-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of John Shott
Sent: Friday, 12 April 2013 1:48 AM
To: Labnetwork
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




_______________________________________________
labnetwork mailing list
labnetwork at mtl.mit.edu
https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork