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SiH4 diluted in Helium poses pumping challenges. Helium is notoriously hard to pump with a turbo and the large amount of mixture needed to grow Si films leads to problems with pressure control and deposition rates. I know I will attract some arguments against
using 100% SiH4 but the main reason to use a pure mixture is to reduce the amount of cylinder changes that are well documented as being the main source of accidents.</div>
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Equipment Dood.</div>
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Steve Paolini</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> on behalf of Nathan Aultman <naultman@creol.ucf.edu><br>
<b>Sent:</b> Monday, April 7, 2025 10:49 AM<br>
<b>To:</b> labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] PECVD dilute gas question(s)</font>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">Hello Labnetwork,</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">We have a PECVD system using dilute silane (2%)/N2. Some labs with similar systems use dilute silane (5%)/helium. We are nearing the end of our current cylinder and will need a replacement soon. What
are the advantages and disadvantages when choosing the dilute gas? Does choosing a helium mixture produce more desirable films and/or quality? In other words, is it worth it to purchase a cylinder with helium? Also, what would be the reason(s) for using
helium as an additional process gas? E.g., a separate MFC and gas line.</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">Thank you all in advance.</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Times New Roman",serif">Nathan C. Aultman</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Times New Roman",serif">University of Central Florida</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Times New Roman",serif">407-823-6852</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt; font-family:"Times New Roman",serif"><a href="mailto:naultman@creol.ucf.edu"><span style="color:#0563C1">naultman@creol.ucf.edu</span></a></span></p>
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