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<p class="MsoNormal">Vibhor,<o:p></o:p></p>
<p class="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.<o:p></o:p></p>
<p class="MsoNormal"> Hope this helps,<o:p></o:p></p>
<p class="MsoNormal"> Steve Paolini<o:p></o:p></p>
<p class="MsoNormal"> Equipment Dood<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:14.0pt">Steve Paolini<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Principal Equipment Engineer<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Harvard University Center for Nanoscale Systems<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">11 Oxford St.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">Cambridge, MA 02138<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">617- 496- 9816<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">spaolini@cns.fas.harvard.edu<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:14.0pt">www.cns.fas.harvard.edu</span><span style="font-size:14.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> <b>
On Behalf Of </b>Vibhor Kumar<br>
<b>Sent:</b> Friday, August 20, 2021 1:49 PM<br>
<b>To:</b> labnetwork@mtl.mit.edu<br>
<b>Subject:</b> [labnetwork] Spot issue in Unaxis-750 PECVD<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:black;background:white">Hello Everyone,</span><span style="font-size:12.0pt;color:black">
<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="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">
<o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Verdana",sans-serif;color:#0B5394"><o:p> </o:p></span></p>
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<p class="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"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Verdana",sans-serif;color:#0B5394"><o:p> </o:p></span></p>
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<p class="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"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Verdana",sans-serif;color:#0B5394"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="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"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="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"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="xgmaildefault"><span style="font-family:"Arial",sans-serif;color:black;background:white">Thanks,</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="xgmaildefault"><span style="font-family:"Arial",sans-serif;color:black;background:white">-Vibhor Kumar-</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="xgmaildefault"><span style="font-family:"Arial",sans-serif;color:black;background:white">Postdoctoral Associate</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span class="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"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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