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Rick Morrison,<br>
<br>
The NanoLab (which has superseded the Microlab) at UC Berkeley has a
good amount of experience with lpcvd SiN films, both stoiciometric
and low-stress. Given our experience I do not recommend using any
kind of trap in the pump manifold between the process tube and the
pump. Adding a trap to the foreline will concentrate pyrophoric
residues. Without frequent cleaning such traps become a significant
safety hazard. At best, cleaning a foreline traps is no fun and
doing this when the material is pyrophoric is even less fun. We are
getting excellent pump lifetime (years) with our Edward iQDP80's
without a foreline trap.<br>
<br>
Heat tracing is a common recommendation for the pump lines of lpcvd
nitride furnaces. We purposefully do not heat our foreline. We've
found running an unheated foreline has advantageous. Forelines
condense and trap effluent. A heated foreline results in the
volatilization of trapped effluents (DCS, i.e. H2SiCl2 and it
fractions) which will back-stream into the process tube and "cvd"
particles onto substrates during loading. While we do not heat our
manifold we do use a "Tystar Corp-modified", heated HPS "Jalapeno
series" valve (200 C). This valve is unique. The Tystar Corp valve
modification allows for continuous pumping of a small volume of gas
while wafers are loaded preventing back-diffusion of effluent from
the pump manifold. It also has a self-cleaning flow orifice. It is a
significant improvement for SiN particle management. I recommend you
contact Henry Heidbreder for more information, <a
moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:henryh@tystar.com">henryh@tystar.com</a><br>
<br>
As for how to deal with process-created H2, the Ebara, Edwards and
other dry pumps use considerable N2 purge during operation,
typically ~35 slpm. These pumps provide an interlock via their
interface module which can be used to disable DCS flow in the event
of low N2 flows. Purge N2 will reduce the H2 concentration well
below the ~4% lower flammable limit (LFL) for H2 in air. It is good
practice to "marry" a pumps exhaust connection to a main duct in a
high-flow area of the exhaust duct further reducing concentrations
well below the flammable limits. (I have seen the LFL sometimes
listed as the LEL (lower explosive limit); however, the LEL for H2
in air is higher than the LFL, ~17%). <br>
<br>
I defer to others with more process knowledge about issues with Pt
and nitride deposition.<br>
<br>
Bob Hamilton<br>
<br>
<p class="MsoNormal">Robert M. Hamilton<br>
Marvel NanoLab<br>
University of CA at Berkeley<br>
Rm 520 Sutardja Dai Hall <br>
Berkeley, CA 94720-1754 <br>
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:bob@eecs.berkeley.edu">bob@eecs.berkeley.edu</a>
(e-mail preferred) <br>
510-809-8600 510-325-7557 (Emergencies)
</p>
<br>
On 4/11/2012 5:08 AM, Morrison, Richard H., Jr. wrote:
<blockquote
cite="mid:D3862732F46DEB4B93B4A7A80614D28802B754@mbx2.draper.com"
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<div class="WordSection1">
<p class="MsoNormal">Hi Everyone,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am restarting a Silicon Nitride LPCVD
process and I have a few questions. The process will use a
EBARA dry pump therefore should I use a trap on the vacuum
pump inlet to catch any particulate generated?
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any issue with excess hydrogen from the
process going into the dry pump, do I need a burn box on the
vacuum pump exhaust?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">2<sup>nd</sup> question has anybody tried
to run the LPCVD process on a wafer with a platinum metal
pattern on the surface? I was wondering if there maybe some
adverse effect because of the catalytic nature of Platinum.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal">Rick<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rick Morrison<o:p></o:p></p>
<p class="MsoNormal">Senior Member Technical Staff <o:p></o:p></p>
<p class="MsoNormal">Group Leader Microfabrication Operations<o:p></o:p></p>
<p class="MsoNormal">Draper Laboratory<o:p></o:p></p>
<p class="MsoNormal">555 Technology Square<o:p></o:p></p>
<p class="MsoNormal">Cambridge, MA 02139<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">W 617-258-3420<o:p></o:p></p>
<p class="MsoNormal">C 508-930-3461<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<br>
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