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Hi V,<br>
<br>
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:<br>
<br>
Do you <i>have</i> a load-lock on this system? When you say
indigenous, you mean more or less "home-built", yes?<br>
<br>
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. <br>
<br>
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).<br>
<br>
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.<br>
<br>
If you can forward more details about this system, I think it will
be easier to give you some better suggestions.<br>
<br>
<br>
Mac Hathaway<br>
Process Engineer and Safety Officer<br>
Center for Nanoscale Systems<br>
Harvard University<br>
<br>
<br>
<br>
On 3/24/2014 7:43 PM, <a class="moz-txt-link-abbreviated" href="mailto:vanaparthy@ee.iitb.ac.in">vanaparthy@ee.iitb.ac.in</a> wrote:
<blockquote
cite="mid:dbbff2f84e0f6ce1c221f9fce3e63a0a.squirrel@sandesh.ee.iitb.ac.in"
type="cite">
<pre wrap=""> 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.
</pre>
</blockquote>
<pre wrap="">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, <a class="moz-txt-link-rfc2396E" href="mailto:vanaparthy@ee.iitb.ac.in">"vanaparthy@ee.iitb.ac.in"</a> <a class="moz-txt-link-rfc2396E" href="mailto:vanaparthy@ee.iitb.ac.in"><vanaparthy@ee.iitb.ac.in></a>
wrote:
</pre>
<pre wrap="">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
</pre>
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