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<p class="MsoNormal">Both water and N2 are part of photochemical reaction.<o:p></o:p></p>
<p class="MsoNormal"><a href="https://www.microchemicals.com/technical_information/exposure_photoresist.pdf">https://www.microchemicals.com/technical_information/exposure_photoresist.pdf</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Bubbles formed in the resist under exposure are nitrogen. Hydration is only tangentially related, as lack of moisture calls for longer exposure times and overexposure of top layers which get hydrated first. I believe N2 can still be split
off without water, but soluble molecule doesn’t form without H2O. My understanding is that normal resist exposure doesn’t involve 100% reaction.
<o:p></o:p></p>
<p class="MsoNormal">Hydration process time goes as resist thickness squared; If I remember correctly, 1 micron calls for 5-10 second of exposure to air at normal humidity; 7 micron would be on the order of 5 minutes. The only case when I really had to care
was dealing with chemically amplified 25 micron resist. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<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>Daniel Lloyd<br>
<b>Sent:</b> Friday, November 5, 2021 06:18<br>
<b>To:</b> Morrison, Richard H., Jr <rmorrison@draper.com>; Maduzia, Joseph Walter <jmaduzi2@illinois.edu>; labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] PR bubbles where exposed<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I’ve seen similar bubbles in the past, but not consistently. While I’m aware that the clean room I have access to is only loosely humidity controlled, what should be an acceptable range. The resist I use doesn’t mention
anything. My relaxation time between pre-bake and exposure is typically 1 hour to let the substrates cool, does anyone have a guide to working that out?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:2.0pt"><span lang="EN-GB" style="font-size:9.0pt;color:#1F497D">Daniel Lloyd<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom:2.0pt"><span lang="EN-GB" style="font-size:9.0pt;color:#1F497D">Development Engineer,<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>>
<b>On Behalf Of </b>Morrison, Richard H., Jr<br>
<b>Sent:</b> 04 November 2021 15:45<br>
<b>To:</b> Maduzia, Joseph Walter <<a href="mailto:jmaduzi2@illinois.edu">jmaduzi2@illinois.edu</a>>;
<a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> Re: [labnetwork] PR bubbles where exposed<o:p></o:p></p>
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<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">HI,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">These look like Nitrogen bubbles, how thick is the resist? Is the thickness in the recommended range?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">We have this issue when the humidity is out of control, we solved the issue by reducing the thickness, to be in the recommended range and changing the prebake per advice form the resist supplier.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Rick<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Richard Morrison<o:p></o:p></p>
<p class="MsoNormal">PMTS<o:p></o:p></p>
<p class="MsoNormal">Draper Laboratory<o:p></o:p></p>
<p class="MsoNormal">555 Technology Square<o:p></o:p></p>
<p class="MsoNormal">Cambridge Ma 02139<o:p></o:p></p>
<p class="MsoNormal">Office: 617-258-3420<o:p></o:p></p>
<p class="MsoNormal">Cell: 508-930-3461<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>>
<b>On Behalf Of </b>Maduzia, Joseph Walter<br>
<b>Sent:</b> Thursday, November 4, 2021 9:59 AM<br>
<b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> [labnetwork] PR bubbles where exposed<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hello All!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="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!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="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.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank You,<o:p></o:p></p>
<p class="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">jmaduzi2@illinois.edu</a><o:p></o:p></p>
<p class="MsoNormal"><a href="https://cleanroom.mechse.illinois.edu/">https://cleanroom.mechse.illinois.edu/</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" style="width:1.3958in;height:.3645in" id="Picture_x0020_1" src="cid:image001.png@01D7D22E.F98A7BD0"></span></a><span style="color:black"><br>
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</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><o:p></o:p></p>
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<p class="MsoNormal">Notice: This email and any attachments may contain proprietary (Draper non-public) and/or export-controlled information of Draper. If you are not the intended recipient of this email, please immediately notify the sender by replying to
this email and immediately destroy all copies of this email. <o:p></o:p></p>
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