[labnetwork] Query on safety concern

[vanaparthy at ee.iitb.ac.in]

 Hi Mac,
Thanks.
  Can some one suggest,
 1.For plasma post treatment that would de-activate the
 phosphine/diborane before opening the reactor each time with out
effecting samples.
2. Is there any best known procedure is there for number of pump/purge
cycles before opening the reactor each time.

-- 
Thanks & Regards,
V.RAJENDRA PRASAD
  Lab Manager,
  CEN,IITBNF, Electrical Engg Dept, Annexe,
  IIT Bombay, Mumbai, Powai- 400076
  Tel No. 9930621667


> Hi V,
>
> So, I'm sure others here have more direct experience with diborane and
> phosphine systems than I have, but just to clarify a couple of points:
>
> Do you /have/ a load-lock on this system?  When you say indigenous, you
> mean more or less "home-built", yes?
>
> If you have a load-lock, why do you prefer not to use it?  If this unit
> is home-built, perhaps it does not have some of the more advanced
> features of a commercial unit, such as gas-flow interlocks, to prevent
> flow of gases into the chamber when the chamber is open.  If it does not
> have such interlocks, you have a very dangerous system on your hands,
> which perhaps could be retrofitted with these features.
>
> To re-emphasize what Len said, I would venture to say diborane and
> phosphine are among the most deadly gases in most cleanrooms.  You
> really want to consider this when coming up with your operating
> procedures.  Opening phospine/diborane process chambers, for whatever
> reason, is typically a very involved procedure, which very carefully
> defined steps to maximize safety and minimize exposure to the gases
> involved (including lingering chamber fumes).
>
> I haven't found any particular ones in discussions here, but there may
> be some plasma post treatment that would de-activate the
> phosphine/diborane before opening the reactor each time.  Otherwise,
> just lots of pump/purge cycles.  For regular sample loading, a load-lock
> would be best.
>
> If you can forward more details about this system, I think it will be
> easier to give you some better suggestions.
>
>
> Mac Hathaway
> Process Engineer and Safety Officer
> Center for Nanoscale Systems
> Harvard University
>
>
>
> On 3/24/2014 7:43 PM, vanaparthy at ee.iitb.ac.in wrote:
>>   Hi Leonard ,
>>   Thanks,We installed Gas detection system in loading
>> area to take care  of any issue with toxic gas is detected,appropriate
>> alarms and evacuations will be initiated.
>>
>>
> V,
>
> Diborane and Phosphine gases are very toxic and deadly...
>
> I'm not sure why you are not using the ll's for sample transfer.  It would
> appear that an SOP would employ the use of load locks to create a barrier
> between the reaction chamber and the outside world.  I would be concerned
> about a failure in your gas delivery system or even outgassing during the
> opening of the process chamber.
>
> 5X N2 pump purges in my opinion is not nearly enough.  A typical pump
> purge for toxic gas cylinder changes is at least 25x.  Are you using a
> Nederman style snorkel exhaust or any fume exhaust abatement whilst
> unloading your samples?  Are you using any PPE or supplied air masks?
>
> You may want to consider keeping your process chamber under vacuum to keep
> its integrity. Ambient moisture from atmosphere upon opening the chamber
> will surely create unwanted fumes and contaminates.
>
> How large is chamber?
>
> Thank you,
>
> -Len
>
> Leonard E. Olona
> University Cleanroom Manager
> University of Oklahoma
> 110 West Boyd Street Rm 550
> Norman, Oklahoma  73019
> D: +1- 405 325-4374
> C: +1- 405 630-9068
> F: +1- 405 325-7066
>
>
>
>
>
>
>
>
>
>
> On 3/24/14 10:40 AM,"vanaparthy at ee.iitb.ac.in"  <vanaparthy at ee.iitb.ac.in>
> wrote:
>
>
> Hello,
>
>
> We have a indigenous Plasma Immersion Ion Implantation system in our lab
> which is capable to P(B2H6) and n(PH3) type of implantation. We are not
> using the load lock for loading/Unloading the sample, Execute this by
> venting the process chamber to atmosphere. Before unloading the sample we
> do the pump purge with N2 gas  for five times.
>
> Is the above procedure followed by us is a standard procedure or do we
> need to follow some more safety precautions before opening the chamber.
>
> Please advise.
>
>
>
> --
> Thanks&  Regards,
> V.RAJENDRA PRASAD
>   Lab Manager,
>   CEN,IITBNF, Electrical Engg Dept, Annexe,
>   IIT Bombay, Mumbai, Powai- 400076
>   Tel No.+91 9930621667
>
>
>
>
>
>
>