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<div class="moz-cite-prefix">Errol Porter,<br>
<br>
Sidestepping the safety issues of trapping pyrophorics in a
confined spare (see my last paragraph about this): I suspect a
cryopump would not perform well unless one could assure residual
H2 levels were minimized. A good deal of H2 is produced in the
disassociation of hydrides. Cryopumps use an activated
carbon-array (aka "Christmas tree") as the ~12 K stage to
physio-adsorb and trap non-condensible gases (such as H2). Thus,
they have finite limitation on the total volumes for such gases.
It is often the H2 capacity of a cryo that drives the need for
regenerations. Besides CVD, H2 is a product of in PVD processes
because sputtered (or evaporated) metals react with residual water
vapor inherent on surfaces producing both an oxide and H2. <br>
<br>
Cryopumps have the option of equipping the vent with a gas tight
overpressure/vent port so effluents are properly routed to a fume
exhaust system and remediation equipment. This prevents the vent
from discharging to an area an area with personnel.<br>
<br>
More importantly, your query begs the question why not use the
turbo to maintain base pressure when the system is in standby? To
present a corollary, I would not want to operate our lab with a
pump that might inadvertently become the equivalent of a silane
cylinder, out of a gas cabinet, connected to a tool. One failure
of gate valves are flakes getting onto the o-ring resulting in a
leak across the seat. Such flakes are common in deposition
systems. Such a leak would result in a reactive load within the
cryo.<br>
<br>
Bob Hamilton<br>
<pre class="moz-signature" cols="60">Bob Hamilton
Marvel NanoLab
University of CA at Berkeley
Rm 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>
(e-mail preferred)
510-809-8600
510-325-7557 (mobile - emergencies)
</pre>
On 12/6/2012 8:31 AM, Errol V. Porter wrote:<br>
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<p class="MsoNormal">Greetings members,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I wanted to see if there are any members
currently using a cryopump on a CVD tool utilizing any of the
following gases; germane, hydrogen, methane, silane, diborane
or phosphine. Note the main pump being used during processing
is a turbopump with the cryopump being used to keep the tool
under vacuum while the tool is not being operated. If there
are any users using a similar configuration, how was the pump
installed specifically to deal with the effluent that is
released during a normal regeneration cycle.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Errol Porter<o:p></o:p></p>
<p class="MsoNormal">University of Arkansas / HiDEC<o:p></o:p></p>
<p class="MsoNormal">700 W. Research Center Blvd<o:p></o:p></p>
<p class="MsoNormal">Fayetteville, AR 72701<o:p></o:p></p>
<p class="MsoNormal">Tel. 479 575-2519<o:p></o:p></p>
<p class="MsoNormal">Fax 479 575-2719<o:p></o:p></p>
<p class="MsoNormal">email:<span style="color:#1F497D"> <a
moz-do-not-send="true" href="mailto:evporte@uark.edu">
<span style="color:blue">evporte@uark.edu</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><a
moz-do-not-send="true" href="http://www.hidec.uark.edu"><span
style="color:blue">http://www.hidec.uark.edu</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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