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Hi David,</div>
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Nothing is changed recently. </div>
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We are using ULSI grade CF4. </div>
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For leak check, I have evacuated the silane gas line and found no leak. Is there any other method you would like to suggest? </div>
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Sure, I will discuss with my superiors and contact Plasma-Therm. </div>
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Thanks,</div>
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-Vibhor-</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Lishan, David (Plasma-Therm LLC) <david.lishan@plasmatherm.com><br>
<b>Sent:</b> Monday, August 23, 2021 8:29 AM<br>
<b>To:</b> April, Mark R. <mapril@draper.com>; Paolini, Steven <spaolini@cns.fas.harvard.edu>; Vibhor Kumar <vk409@soe.rutgers.edu>; labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> RE: Spot issue in Unaxis-750 PECVD</font>
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<p class="x_MsoNormal">Hi Vibhor,</p>
<p class="x_MsoNormal">The imprint of the showerhead hole pattern is often an indication that silane is reacting with residual oxygen somewhere behind the showerhead. The source of the oxygen could be a leak anywhere from behind the showerhead all the back
to the main valves of the gas bottles. If the CF4 clean gas is a premix of CF4/O2, it is possible that the oxygen is coming from there. If there is small leak and the system has been left idle overnight, it is generally the first run of the day that shows
the most pronounced imprint pattern. Subsequent runs can show a less pronounced pattern. Perhaps this is what has been described in the original problem statement.
</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Has anything been recently changed on the system e.g. silane gas bottle, mass flow controller or gas line?</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Suggest contacting Plasma Therm Tech Support if the problem persists.
</p>
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<p class="x_MsoNormal"><span style="color:black">BR,</span></p>
<p class="x_MsoNormal"><span style="color:black">David</span></p>
<p class="x_MsoNormal"><span style="color:#820024"> </span></p>
<p class="x_MsoNormal"><span style="color:#820024">David Lishan, Ph.D., Sr. Member IEEE</span></p>
<p class="x_MsoNormal"><span style="color:#595959">Principal Scientist, Director – Technical Marketing</span></p>
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<p class="x_MsoNormal"><b>From:</b> labnetwork [mailto:labnetwork-bounces@mtl.mit.edu]
<b>On Behalf Of </b>April, Mark R.<br>
<b>Sent:</b> Monday, August 23, 2021 6:48 AM<br>
<b>To:</b> Paolini, Steven <spaolini@cns.fas.harvard.edu>; Vibhor Kumar <vk409@soe.rutgers.edu>; labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] Spot issue in Unaxis-750 PECVD</p>
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<p class="x_MsoNormal"><span style="color:black">Good Morning Vibhor,</span></p>
<p class="x_MsoNormal"><span style="color:black">I concur with Mr. Paolini. I had a similar issue on a PECVD tool. After a thorough shower head clean, including the diffuser plate, the shower head pattern was eliminated. This routinely gets done each year
now, during a major PM. You may need to perform more due to your usage.</span></p>
<p class="x_MsoNormal"><span style="color:black">Hope this helps.</span></p>
<p class="x_MsoNormal"><span style="color:black"> </span></p>
<p class="x_MsoNormal"><b><span style="font-size:9.0pt; color:#1F497D">Mark R. April</span></b><span style="font-size:8.0pt; font-family:"Cambria",serif; color:#1F497D"><br>
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<p class="x_MsoNormal"><b>From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>>
<b>On Behalf Of </b>Paolini, Steven<br>
<b>Sent:</b> Friday, August 20, 2021 4:02 PM<br>
<b>To:</b> Vibhor Kumar <<a href="mailto:vk409@soe.rutgers.edu">vk409@soe.rutgers.edu</a>>;
<a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> Re: [labnetwork] Spot issue in Unaxis-750 PECVD</p>
</div>
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<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Vibhor,</p>
<p class="x_MsoNormal"> You are most likely seeing the effect of the showerhead being in need of cleaning, particularly the backside. The Deposition of dielectric films creates a powdery substance just outside of the intended plasma concentrate. This debris,
over time, will allow small reactions to happen under the showerhead and show up as spots on your wafer, most likely in the pattern of the holes in the showerhead. I would suggest removing the showerhead and diffuser plate and performing a very thorough clean
on all the parts. In my experience, and depending on the usage, this should be performed routinely at an interval that keeps the effect at bay.</p>
<p class="x_MsoNormal"> Hope this helps,</p>
<p class="x_MsoNormal"> Steve Paolini</p>
<p class="x_MsoNormal"> Equipment Dood</p>
<p class="x_MsoNormal"> </p>
<div>
<p class="x_MsoNormal"><span style="font-size:14.0pt">Steve Paolini</span></p>
<p class="x_MsoNormal"><span style="font-size:14.0pt">Principal Equipment Engineer</span></p>
<p class="x_MsoNormal"><span style="font-size:14.0pt">Harvard University Center for Nanoscale Systems</span></p>
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<p class="x_MsoNormal"><span style="font-size:14.0pt"><a href="mailto:spaolini@cns.fas.harvard.edu">spaolini@cns.fas.harvard.edu</a></span></p>
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<div style="border:none; border-top:solid #E1E1E1 1.0pt; padding:3.0pt 0in 0in 0in">
<p class="x_MsoNormal"><b>From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>>
<b>On Behalf Of </b>Vibhor Kumar<br>
<b>Sent:</b> Friday, August 20, 2021 1:49 PM<br>
<b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> [labnetwork] Spot issue in Unaxis-750 PECVD</p>
</div>
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<p class="x_MsoNormal"> </p>
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<p class="x_MsoNormal"><span style="font-family:"Arial",sans-serif; color:black; background:white">Hello Everyone,</span><span style="font-size:12.0pt; color:black">
</span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; color:black"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">During nitride/oxide deposition with <b>Unaxis-750 PECVD</b>, we are getting a mirror image of shower head
on the wafer, i.e., spots. We cleaned the chamber with CF4 for 2 consecutive days, each day 4:30 hrs. The conditions were </span></span><span style="font-size:12.0pt; color:black">
</span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; font-family:"Verdana",sans-serif; color:#0B5394"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif; color:black">CF4 = 100 sccm, Temp = 250 C, chamber pressure = 600 mT, time = 4:30 hrs </span><span style="font-size:12.0pt; font-family:"Verdana",sans-serif; color:#0B5394"></span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; font-family:"Verdana",sans-serif; color:#0B5394"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-family:"Arial",sans-serif; color:black">We also evacuated the silane gas line, but there is no leakage.</span><span style="font-size:12.0pt; font-family:"Verdana",sans-serif; color:#0B5394"></span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; font-family:"Verdana",sans-serif; color:#0B5394"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">After completing the cleaning, when we conditioned the chamber and deposited nitride, the spots were lightened.
But on the second day, the spots look enlarging again.</span></span><span style="font-size:12.0pt; color:black"></span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; color:black"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">Can anyone please suggest solution to this issue? </span></span><span style="font-size:12.0pt; color:black"></span></p>
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<p class="x_MsoNormal" style="background:white"><span style="font-size:12.0pt; color:black"> </span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">Thanks,</span></span><span style="font-size:12.0pt; color:black"></span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">-Vibhor Kumar-</span></span><span style="font-size:12.0pt; color:black"></span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">Postdoctoral Associate</span></span><span style="font-size:12.0pt; color:black"></span></p>
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<p class="x_MsoNormal" style="background:white"><span class="x_xgmaildefault"><span style="font-family:"Arial",sans-serif; color:black; background:white">Rutgers, The State University of New Jersey. </span></span><span style="font-size:12.0pt; color:black"></span></p>
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