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The plasma will etch the glass viewport over time. If the fluoropolymer residue initially deposited on the viewport has some pattern, you'll end up with a funny looking viewport. The solution is simple: order a replacement viewport from the vendor.</div>
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To prevent the viewport from getting damaged again, next time, try placing a 3" round sapphire wafer in front of the glass viewport before sealing it against the chamber. This will make your viewport last forever, and always transparent.</div>
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Cheers,</div>
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Yong Sun</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 Emma Anquillare <eanquillare@gc.cuny.edu><br>
<b>Sent:</b> Wednesday, April 15, 2026 9:37 PM<br>
<b>To:</b> Network Fab <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] What is this??</font>
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Dear LabNetwork,</div>
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I humbly call upon your mighty wisdom! A few weeks ago I noticed what (I thought) was some kind of polymer gunk or residue on the interior of our ICP-F porthole window. (See images attached). We have been running a DRIE/Bosch process every few months, so despite
manual cleans before and after each session it didn't seem too remote that polymer residue could build up on the porthole, which is usually not scrubbed.</div>
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However, when I went to get rid of it during my monthly manual clean of the tool, it wouldn't go away. I tried rubbing it with IPA on a lab wipe, as well as scratching at it more forcefully with IPA-soaked swabs, and even scratching with the rear plastic part
of the swab. It appeared to go away at first when wet, but once the IPA evaporated, I could see I hadn't actually removed anything. My manual scrubs are also followed by a lengthy hour-and-a-half dry clean (O2-50, SF6- 10, 10mT, 20 C, RF- 100W, ICP- 2500 W)
that users also use for a shorter period after each session. I've been managing this tool for about two years now and never seen anything like this. </div>
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Does anyone know what it is, if it's a concern, and if/how I should remove it?</div>
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Thanks!</div>
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Emma</div>
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<b>_____________________________________________</b></div>
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<b>Emma Anquillare, PhD</b></div>
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Research Scientist</div>
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<span style="font-size:12pt">ASRC </span><span style="font-size:16px; background-color:rgb(255,255,255)">Nanofabrication Facility</span></div>
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<span style="background-color:rgb(255,255,255)">City University of New York</span></div>
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<img id="x_image_0" width="337" height="77" style="width:337px; height:77px" data-outlook-trace="F:2|T:2" src="cid:4be531e3-45c8-47e3-ab75-ee86c65b961b"></div>
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<i>Catalyzing Change, Celebrating Gains: </i></div>
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<i>A decade of visionary science for the public good.</i></div>
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