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I guess I am too late to be in first 10 to answer...</div>
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N2 forms as a result of photochemical reaction in DNQ resists. You need slower and/or lower exposure to generate less N2 and allow it to dissipate</div>
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Last paragraph in this link describes the problem:</div>
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<a href="https://www.allresist.com/resist-wiki-why-may-air-bubbles-develop-in-photoresist-films-and-how-can-they-be-avoided/" id="LPlnkOWALinkPreview">https://www.allresist.com/resist-wiki-why-may-air-bubbles-develop-in-photoresist-films-and-how-can-they-be-avoided/</a></div>
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<a target="_blank" id="LPUrlAnchor980873" href="https://www.allresist.com/resist-wiki-why-may-air-bubbles-develop-in-photoresist-films-and-how-can-they-be-avoided/" style="text-decoration: none; color: var(--themePrimary);">7. Why may air bubbles develop in
photoresist films, and how can they be avoided? - Allresist EN</a></div>
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Luftbläschen nach dem Aufschleudern sind meist Luftbläschen, z.B. wenn die Lackflasche vor der Beschichtung geschüttelt bzw. stärker bewegt wurde oder der Lack verdünnt wurde. Beschichtungen nach unmittelbarer Öffnung der Flaschen, insbesondere vor einem Temperaturausgleich
können ebenfalls zu Luftblasen führen.</div>
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www.allresist.com</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 Maduzia, Joseph Walter <jmaduzi2@illinois.edu><br>
<b>Sent:</b> Thursday, November 4, 2021 9:59 AM<br>
<b>To:</b> labnetwork@mtl.mit.edu <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> [labnetwork] PR bubbles where exposed</font>
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<p class="x_MsoNormal">Hello All!</p>
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<p class="x_MsoNormal">Thank you again for all your feedback on SiO2 etch around Al. It has been very helpful and we are moving down multiple paths suggested via the Lab Network to try to solve the issue. More to come once we solve it!</p>
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<p class="x_MsoNormal">I have another issue I was hoping for feedback on. We have bubbling in our PR (SPR-220-4.5) (pos tone) that we haven’t been able to track the source of. It only bubbles during exposure and only where it is exposed. Unexposed areas are
unaffected. I’ve attached some images of the bubbling where you can see the exposed (lighter) and unexposed (darker) areas. The bubbles are visible to the naked eye. The wafer is silicon w a dry thermally grown SiO2 surface. We typically expose via EV620 mask
aligner with Vac+HardContact. However, even in a flood exposure with the mask just set lightly down it still bubbles. Without a mask there are also bubbles randomly distributed across the wafer, but they don’t get stuck to the mask so they don’t pop. We tried
various pre-bakes, HMDS coat vs not, piranha treat vs not. In the past these bubbles show up, we trial and error to get rid of them and suddenly they disappear. Our process, although seemingly repeatable, does not yield repeatable results.
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<p class="x_MsoNormal">Thank You,</p>
<p class="x_MsoNormal"><b><span style="color:#13294B; text-transform:uppercase">JOE MADUZIA</span></b><span style="color:black"><br>
</span><i><span style="color:#13294B">MNMS Laboratory Specialist</span></i><span style="color:black"><br>
<br>
</span><span style="color:#13294B">The Grainger College of Engineering</span><span style="color:black"><br>
</span><span style="color:#13294B">Mechanical Science and Engineering</span><span style="color:black"><br>
<br>
</span><span style="color:#13294B">2239 Sidney Lu Mechanical Engineering Bldg</span><span style="color:black"><br>
</span><span style="color:#13294B">1206 W. Green</span><span style="color:black"><br>
</span><span style="color:#13294B">Urbana, IL 61801</span><span style="color:black"><br>
</span><span style="color:#13294B">217.244.6302 | </span><a href="mailto:jmaduzi2@illinois.edu"><span style="color:#0563C1">jmaduzi2@illinois.edu</span></a></p>
<p class="x_MsoNormal"><a href="https://cleanroom.mechse.illinois.edu/"><span style="color:#0563C1">https://cleanroom.mechse.illinois.edu/</span></a><span style="color:black"><br>
<br>
</span><a href="http://illinois.edu/"><span style="color:windowtext; text-decoration:none"><img border="0" width="134" height="35" id="x_Picture_x0020_1" style="width:1.3958in; height:.3645in" data-outlook-trace="F:1|T:1" src="cid:image001.png@01D7D156.50D75180"></span></a><span style="color:black"><br>
<br>
</span><i><span style="color:#666666">Under the Illinois Freedom of Information Act any written communication to or from university employees regarding university business is a public record and may be subject to public disclosure.</span></i></p>
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