[labnetwork] expired process gas

Mon Jan 12 14:12:43 EST 2015

Just to add a little anecdotal information into the mix, we had an interesting experience (interesting but not surprising) on moving a laser system from the old building - with old, not so careful plumbing - to the BNC. We found that the laser gases lasted an order of magnitude longer with the new plumbing. The new system had very low moisture and oxygen intrusion, which supports Bob's comment about the interaction with the steel cylinder walls. As we all have experienced, those interactions are exacerbated by the presence of moisture (and to a lesser extent oxygen). We therefore believe that the reason that the gas had a dramatically longer lifetime is that it maintained its purity longer. This, then, calls into question the lifetime generalities given by the gas suppliers.

John

John R. Weaver
Strategic Facilities Officer
Birck Nanotechnology Center
1205 West State Street
West Lafayette IN 47907
(765) 494-5494
jrweaver at purdue.edu<mailto:jrweaver at purdue.edu>
nano.purdue.edu

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Bob Hamilton
Sent: Monday, January 12, 2015 10:53 AM
To: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] expired process gas

Colleagues,

Following up on Kamal's 1/9 post, in the case of excimer laser gas the expiration date is critical. This is confirmed by higher firing voltages, (bad) required with old excimer mix.

As in the case of eximcer gas, acid gases react with steel cylinder walls. I would argue smaller cylinders, with a larger surface-to-volume ratio exacerbate this situation. This, along with the often higher price for smaller cylinders is another argument against "smaller is better (safer)" when discussing reactive gas cylinders.

In the case of diborane, its stability vs. time is influenced by its percentage and the diluent it is mixed with. From memory diborane's equilibrium is better in H2 than in SiH4. When, after years of use, plumbing for a diborane delivery line is reviewed, one sees the higher order borane polymers coating surfaces. This is an argument to routine evacuate the gas-stick (valves, mfc, P xducer, etc.) post deposition.

Bob Hamilton

--

Robert Hamilton

University of California at Berkeley

Marvell NanoLab

Equipment Eng. Mgr.

Room 520 Sutardja Dai Hall

Berkeley, CA 94720-1754

bob at eecs.berkeley.edu<mailto:bob at eecs.berkeley.edu>

Phone: 510-809-8600

Mobile: 510-325-7557 (Emergencies only poor cell phone service in lab)e-mail preferred

On 1/9/2015 11:47 PM, Kamal Yadav wrote:

Hi,

I was also trying to find the affects of
expiration of NH3 and Diborane in Hydrogen and silane.

In pure gases it does not matter and you can use after expiration  we have used 6 years post expiration for NH3.  When we changed new cylinder process did not improve... So it does not matter.

In Diborane mixtures or similar I have been told that the ratio is not maintained post expiration..

Thanks,
Kamal
IITBNF
On Jan 10, 2015 3:45 AM, "Himmer, Phil" <PhilH at ee.montana.edu<mailto:PhilH at ee.montana.edu>> wrote:
Hello

Thanks to all for your input about the expired gas. The general consensus is that expiration dates are not relevant for process stability so I'll continue using what I have.

regards
phil

Dr. Phillip Himmer
Manager Montana Microfabrication Facility
Montana State University
Bozeman Mt 59717

Office Ph: 406-994-7178<tel:406-994-7178>
email: philh at ece.montana.edu<mailto:philh at ece.montana.edu>

On Jan 7, 2015, at 2:44 PM, Janney, Peter J. <janney.9 at osu.edu<mailto:janney.9 at osu.edu>> wrote:

It's my understanding that the gas doesn't really expire, it's only the certification on the tank.

--
Pete Janney

-------- Original message --------
From: "Himmer, Phil"
Date:01/07/2015 2:14 PM (GMT-05:00)
To: labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Subject: [labnetwork] expired process gas

Hello,

Does anyone have any practical experience using Chlorine and Hydrogen Bromide gas past it's expiration date? We use the gas for ICP etching of chrome and aluminum.
We have small cylinders(air liquide 7-size) of each that still have gas in them but are now years past the expiration date. I have pulled them from the gas cabinet with the plan to replace them but am having difficulty finding a vendor who offers these gasses in these small volumes. We are trying to not use lecture bottles due to disposal considerations.

looking forward to suggestions
phil

Dr. Phillip Himmer
Manager Montana Microfabrication Facility
Montana State University
Bozeman Mt 59717

Office Ph: 406-994-7178<tel:406-994-7178>
email: philh at ece.montana.edu<mailto:philh at ece.montana.edu>

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--

Robert Hamilton

University of California at Berkeley

Marvell NanoLab

Equipment Eng. Mgr.

Room 520 Sutardja Dai Hall

Berkeley, CA 94720-1754

bob at eecs.berkeley.edu<mailto:bob at eecs.berkeley.edu>

Phone: 510-809-8600

Mobile: 510-325-7557 (Emergencies only poor cell phone service in lab)e-mail preferred

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