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Tom Britton,<br>
<br>
Thank you for your insight. <br>
<br>
The Marvell NanoLab is about to commission an HCl feed to an epi
system. We are planning to add a purifier in series with the pigtail
from the cylinder to the panel. When one installs such a purifier is
it normal practice to plumb a shunt around it to use during
trickle-purging/cylinder changes? Although a new term to me, we have
made it a practice to reverse-feed N2 through pigtails, to the DISS,
during cylinder changes, with good benefit.<br>
<br>
Also, if one install a reactive HCl purifier does this give an
opportunity to step-down a level in gas purity for HCl, assuming it
meets a < 1ppm H2O content?<br>
<br>
Bob Hamilton<br>
<pre class="moz-signature" cols="72">--
Robert Hamilton
University of California at Berkeley
Marvell NanoLab
Equipment Eng. Mgr.
Room 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
<a class="moz-txt-link-abbreviated" href="mailto:bob@eecs.berkeley.edu">bob@eecs.berkeley.edu</a>
Phone: 510-809-8600
Mobile: 510-325-7557 (Emergencies only)
e-mail preferred</pre>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix"><br>
<br>
On 6/11/2014 9:20 AM, Tom Britton wrote:<br>
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<p class="MsoPlainText"><span>Hi John,</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span>I'm glad that you found the source
of the leak. Any time a system is compromised it causes huge
issues with down time and cost of repair. As you are
probably aware, your gas line is most likely trashed to the
tool and needs to be replaced to the tool. Don't just
replace the panel and run the gas again, as corrosion
spreads once it starts. Your gas cabinet vendor should be
able to get you a new panel, hopefully quickly, so you're
not down for an excessive time.</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span>In reading what you wrote about
leak checking after install, this shouldn't be necessary.
The major Fabs don't do this as the downtime and cost would
be enormous. The initial installation by your mechanical
contactor includes a helium leak check through the cabinet
to the tool, and if you're performing a cylinder leak check
after every bottle change, you should be fine from a leak
check perspective. Instead focus on keeping the gas dry. It
is well documented that HCL, and most other corrosives, in
the gaseous form, can run for years in stainless steel lines
with no issues, but as soon as there is the slightest trace
of moisture, game over. It's my guess, that when you send
this panel back to the gas cabinet supplier, you're probably
going to hear that the valve corroded through where you
found the leak.
</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span>The major points for using any
corrosive gas are:</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText">
<span><span>1.<span>
</span></span></span><span>Helium leak check the
connection after every cylinder change prior to the
introduction of process gas. We advise using a "He/Inert
Gas" blend for your purge gas, as you can use the purge gas
to helium leak test the connection.</span></p>
<p class="MsoPlainText">
<span><span>2.<span>
</span></span></span><span>Always use DISS fittings for
both the process gas and the purge gas. Not only do they
provide a higher level of leak integrity and purity over a
CGA, but one is less likely to introduce a lower purity
purge gas by mistake than if the connection has a standard
580 CGA on it.</span></p>
<p class="MsoPlainText">
<span><span>3.<span>
</span></span></span><span>Purge Gas Purifier - We highly
recommend a purge gas purifier for all mineral acid gases.
Granted, your cylinder costs $1200, but it's cheap insurance
and it will last a very long time.</span></p>
<p class="MsoPlainText">
<span><span>4.<span>
</span></span></span><span>Trickle Purge Valve - check to
make you have a Trickle Purge Valve in your purge line and
that it's open during bottle changes. This does a good job
of keeping atmosphere from getting into the gas line during
the physical changing of the bottle.</span></p>
<p class="MsoPlainText">
<span><span>5.<span>
</span></span></span><span>Cycle Purges - 30 is not
enough. Set your purge cycles at 60 for both pre and post
purge. The pre-purge is for the safety of the operators, and
does a better job of scrubbing the inside of the tubing and
components of the HCl, so any atmospheric moisture that gets
past the trickle purge doesn't react. The post purge is to
dry the inside of the gas line of the tube and components
before the HCl is reintroduced into the system. Any less and
there is a chance that residual moisture will remain, and
once the HCl gas hits it, the corrosion will start and it's
a matter of time before you see the effects.</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span>I was talking with Troy on this
and he ran his HCl at ON Semi for over 10 years using the
above practice, and some of their systems sat idle for quite
some time between quartz cleaning steps on seldom used
tools. I also talk with a lot of gas systems managers in my
travels and this is a fairly common way that the production
Fabs keep their corrosive systems running and the problems
at bay.</span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span>Hope this helps. See you on
Sunday.</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span>Tom</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span>Tom Britton</span><span></span></p>
<p class="MsoNormal"><span>Director of Sales</span><span></span></p>
<p class="MsoNormal"><i><span>Critical Systems, Inc.</span></i><span></span></p>
<p class="MsoNormal"><span>Direct: 208-890-1417</span></p>
<p class="MsoNormal"><span>Office: 877-572-5515</span></p>
<p class="MsoNormal"><span><a moz-do-not-send="true"
href="http://www.criticalsystemsinc.com/"><i><span>www.CriticalSystemsInc.com</span></i></a></span><i><u><span></span></u></i></p>
<p class="MsoNormal"><i><u><span><span> </span></span></u></i></p>
<p class="MsoNormal"><span><img id="Picture_x0020_1"
src="cid:part2.07040506.00040004@berkeley.edu" alt="logo
for email signature png" height="48" width="245"></span></p>
<p class="MsoNormal"> </p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText"><span> </span></p>
<p class="MsoPlainText">-----Original Message-----<br>
From: <a class="moz-txt-link-abbreviated" href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>
[<a class="moz-txt-link-freetext" href="mailto:labnetwork-bounces@mtl.mit.edu">mailto:labnetwork-bounces@mtl.mit.edu</a>] On Behalf Of John
Shott<br>
Sent: Tuesday, June 10, 2014 2:20 PM<br>
To: Weaver, John R; <a class="moz-txt-link-abbreviated" href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
Subject: Re: [labnetwork] Anhydrous HCl after it escapes ...</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">Labnetwork Community:</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">First, I'd like to thank Chung Wing
Leong, Dennis Grimard, Craig Cheney, Tom Britton and John
Weaver for taking the time to respond to my query.
</p>
<p class="MsoPlainText">I appreciate your collective expertise
and input and am taking a number of things you suggested under
careful consideration as we move forward.</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">In the meantime, we have learned a bit
more about this leak and I thought that I would share with you
a bit more about what we have learned:</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">First, the leak seems to have occurred
at the joint between the valve body and the tube stub ... not,
as we had originally feared and suspected at one of the VCR
connection points. Nor did it occur at one of the orbital
welds between the tube stub on the valve and a VCR gland. </p>
<p class="MsoPlainText">To me it is unusual to see a leak at
that point in a valve ...
</p>
<p class="MsoPlainText">particularly one that has not been in
service very long.</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">Second, this failure occurred downstream
(on the tool side) of the pneumatically-controlled,
low-pressure outlet valve on the panel.
</p>
<p class="MsoPlainText">Certainly on our panel, and in most
auto-purge panels of this type, this valve is typically closed
during bottle changes and similar leak checking activities.
To be candid, this has been a bit of a blind spot for me:
while I told you that we leak check the panel each time that
we change a cylinder (which is true), now that I think about
it more carefully, we don't have a mechanism for leak checking
anything on the downstream side of this valve on a regular
basis.</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">In fact what we normally leak check is
that portion of the panel that is upstream of the
pneumatically-controlled, low-pressure outlet valve.
</p>
<p class="MsoPlainText">Since this is a manifolded cabinet that
has two bottles feeding a single output line, there are
actually a number of potential failure points that we do not
regularly check that includes the output side of each
pneumatically-controlled output valve, the manual quarter-turn
valve in series with and downstream from the
pneumatically-controlled output valve and the fittings
associated with the tee in the manifold. As this cabinet has
not been service for an extended period of time, those
downstream fittings have likely been checked only twice: once
by the cabinet manufacturer at their facility and once by us
during the cabinet install. While our cabinet was helium leak
checked and certified by a third-party to be less than 10^-9
SCCM leakage, is there a chance that we missed something
then? I'm certainly wondering ...</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">My guess is that I am not alone in
having thought that we leak check the entire panel and all
fittings each time we change a gas cylinder ...
</p>
<p class="MsoPlainText">whereas there are likely several
fittings and connection points that are not actually checked
each time. I will certainly think about this in a new light
...</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">Thanks,</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">John</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText">On 6/9/2014 5:43 AM, Weaver, John R
wrote:</p>
<p class="MsoPlainText">> John -</p>
<p class="MsoPlainText">> I've had experiences (certainly
plural :)) with both external and internal leaks. For an
internal leak, where moisture has gained access to the piping,
I have always replaced the piping components up to the point
where the leak was blocked - a valve, etc. I use valves with
Hastelloy wetted surfaces (sometimes called Hastelloy trim),
which is not impervious to HCl corrosion but certainly holds
up better.</p>
<p class="MsoPlainText">> For external leaks, the key is to
neutralize the surfaces as quickly as possible. In one
instance we had to replace many components because we didn't
neutralize the surfaces more quickly. A mild base works well
for neutralization - something with a pH in the 9 range. Then
a thorough rinse to remove any salts is necessary.</p>
<p class="MsoPlainText">> We run all of the gas cabinet
exhausts for chloride gas cabinets through our plastic exhaust
system, so we don't have to worry about exhaust. If you use a
metal exhaust on the gas cabinet where the leak occurred, I'd
carefully inspect the exhaust for a month or two after the
incident.</p>
<p class="MsoPlainText">> I hope this helps.</p>
<p class="MsoPlainText">> John</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> John R. Weaver</p>
<p class="MsoPlainText">> Facility Manager</p>
<p class="MsoPlainText">> Birck Nanotechnology Center</p>
<p class="MsoPlainText">> Purdue University</p>
<p class="MsoPlainText">> <a moz-do-not-send="true"
href="mailto:jrweaver@purdue.edu"><span>jrweaver@purdue.edu</span></a></p>
<p class="MsoPlainText">> nano.purdue.edu</p>
<p class="MsoPlainText">>
________________________________________</p>
<p class="MsoPlainText">> From: <a moz-do-not-send="true"
href="mailto:labnetwork-bounces@mtl.mit.edu"><span>labnetwork-bounces@mtl.mit.edu</span></a>
[<a class="moz-txt-link-abbreviated" href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>]
</p>
<p class="MsoPlainText">> on behalf of John Shott
[<a class="moz-txt-link-abbreviated" href="mailto:shott@stanford.edu">shott@stanford.edu</a>]</p>
<p class="MsoPlainText">> Sent: Thursday, June 05, 2014 3:08
PM</p>
<p class="MsoPlainText">> To: <a moz-do-not-send="true"
href="mailto:labnetwork@mtl.mit.edu"><span>labnetwork@mtl.mit.edu</span></a></p>
<p class="MsoPlainText">> Subject: [labnetwork] Anhydrous HCl
after it escapes ...</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> Labnetwork Community:</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> Sooner or later, it seems,
anhydrous hydrogen chloride (or a number of
</p>
<p class="MsoPlainText">> equally corrosive materials) is
going to escape. At least that is our
</p>
<p class="MsoPlainText">> experience at the Stanford
Nanofabrication Facility. Despite our best
</p>
<p class="MsoPlainText">> efforts to use quality components,
do proper leak checking, etc., it
</p>
<p class="MsoPlainText">> seems as if we end up with a leak
either in a gas cabinet or in a tool
</p>
<p class="MsoPlainText">> near a mass flow controller. At
that point, anything near the site of
</p>
<p class="MsoPlainText">> the original leak has been covered
with now moisture-laden hydrogen
</p>
<p class="MsoPlainText">> chloride ... which, I believe, is
far more corrosive than the original
</p>
<p class="MsoPlainText">> anhydrous material.</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> For those of you who have
encountered similar situations, how do you
</p>
<p class="MsoPlainText">> recover or what to you replace? Do
you have effective means of
</p>
<p class="MsoPlainText">> neutralizing those metal surfaces?
Do your replace VCR gaskets with
</p>
<p class="MsoPlainText">> thicker-than-normal or grooved
"super gaskets"? Do you replace the
</p>
<p class="MsoPlainText">> entire assembly? Do you leak
check, put back in service, and pray?</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> Thanks for sharing your experience
and insights,</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> John</p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">> </p>
<p class="MsoPlainText">>
_______________________________________________</p>
<p class="MsoPlainText">> labnetwork mailing list</p>
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<p class="MsoPlainText">> <a moz-do-not-send="true"
href="https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork">
<span>https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork</span></a></p>
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<p class="MsoPlainText"> </p>
<p class="MsoPlainText">_______________________________________________</p>
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