[labnetwork] RIE Process Gases

[Matthew Moneck]

Hi Cenk,

We try to run ours to a low point, but not quite empty if we can.  For example, we typically run 2000psi cylinders to 200psi then swap the bottle.  For lower pressure cylinders or liquid cylinders measured by weight, we still tend to use that 10% mark as a changeout point, although, admittedly, some cylinders do inadvertently run to complete empty.

That said, cylinders do have a shelf life and most university Environmental Health and Safety groups have their own recommendations on what they consider acceptable.  Many of the semi grade gases “expire” within 3 years.  We have gone well beyond this without any noticeable change in our processes.  However, you have to pay attention to the cylinder itself.  There is a stamped certification date typically imprinted at the top of the cylinder.  This is the date on which the cylinder underwent hydrostatic testing and certification.  Most high pressure gas cylinders are rated 10yrs beyond that date.  If you have a cylinder that is approaching the 10yr mark, send it back (note that your cylinder may not have been filled in year 1, so do not assume that it’s 10yrs past the fill date).

For Cl and other corrosive gases, I believe the limit is typically 5yrs for the cylinder, although, I would need to check that to be 100% sure.  We tend to swap ours out within 2yrs.  You also have to watch for cylinders containing gases that react with the cylinder material itself.  For instance, anhydrous HF used in vapor HF systems can be purchased in steel (i.e. iron) cylinders.  At the time of purchase, the cylinder pressure is only a couple psi or so.  However, if you hold on to one of these bottles for too long, the HF can react with Fe to release hydrogen, causing the cylinder to overpressurize and possibly explode.  It is typically recommended to exchange such cylinder within 2yrs.  For that reason, we use nickel cylinders on this material and still follow the 2yr rule.

Best Regards,

Matt

--
Matthew T. Moneck, Ph.D.
Executive Manager, Claire & John Bertucci Nanotechnology Laboratory
Electrical and Computer Engineering | Carnegie Mellon University
5000 Forbes Ave., Pittsburgh, PA 15213-3890
T: 412.268.5430
F: 412.268.3497
www.ece.cmu.edu<http://www.ece.cmu.edu/>
nanofab.ece.cmu.edu

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Cenk Yanik (Alumni)
Sent: Wednesday, October 09, 2019 2:59 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] RIE Process Gases

Dear All,
We are wondering how often do you change the RIE process gases even the gases are not run out. We have been told that they should be changed in max 3 years even if they are almost full but we have been using some of them (SF6, C4F8, CHF3)  for 5 years and we didn't realize any process-related critical problems during the dry etching process.
Have you ever faced with any problems for Fluorine and Chlorine based gases in your institutes?
We would appreciate if you could share your experiences and regulations considering the shell life of the process gases at your facilities
Best Regards,

--

Cenk YANIK, PhD
Nanofabrication Team Leader
Sabanci University
Nanotechnology Research and Application Center ( SUNUM )
Orta Mahalle, Üniversite Caddesi No: 27 34956 Tuzla - İstanbul
Office:+90 216 483 9994
web: sunum.sabanciuniv.edu<http://sunum.sabanciuniv.edu>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20191009/46e7642a/attachment.html>