[labnetwork] expired process gas

[Bob Hamilton]

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
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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>
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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
Phone: 510-809-8600
Mobile: 510-325-7557 (Emergencies only poor cell phone service in lab)e-mail preferred

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