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

[raghavan]

Dear Guy, John and Fouad
I am very glad to see this discussion on Labnetwork. We at NNFC are also
facing similar issues. 
It turns out, our SPTS DRIE tool pumps will let in N2 only when the process
is running. During the process idle time the N2 flow is turned off. 
We also have Oxford instrument's RIE and PECVD tools which have a 24/7 N2
flow need, a very high consumption. Last week we were informed that Oxfod is
introducing a new software interface to control Nitrogen flow. I will post
the details when I get them.
Regards
Raghavan

*************************************************
Dr.Vijayaraghavan
Technology Manager
National Nanofabrication Centre 
Centre for Nano Science and Engineering
Indian institute of Science ( IISc)
Bangalore - 560 012
India
Ph: 09663304316
***************************************************

 


-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of Lavallee, Guy P.
Sent: 12 April 2013 01:17
To: John Shott; Labnetwork
Subject: Re: [labnetwork] Using CDA, rather than N2, as pump purge in
Bosch-like processes?

John,
   I believe the issue with the Fluorine chemistries is the formation of HF
if you ever have water in the CDA which then gets into the pumps.  The
potential of creating this would obviously be dependent on how much
unreacted fluorine would reach the pump as well as how reactive the
effluents would be with water leading to the formation of HF.   

The other issue you have to think about besides water (which the pumps won't
like either regardless of HF formation) would be the potential of oil being
in the CDA.  This will be highly dependent on the type of CDA system you
have at your facility.   

We have thought about changing from N2 to CDA as well but have been very
hesitate due to the many unknowns and not wanting to risk it.  It would be
interesting to hear others inputs.

Thanks,
Guy

Penn State University's Nanofabrication Laboratory Lead Etch Engineer
Materials Research Institute
N-105 Millennium Science Complex (MSC Bldg) University Park, PA 16802
Email: gpl107 at psu.edu
Phone: 814-865-9339
Cell: 814-777-0719


-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of John Shott
Sent: Thursday, April 11, 2013 11:48 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

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

--
This message has been scanned for viruses and dangerous content by
MailScanner, and is believed to be clean.


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.