<div dir="auto">To add to this - once SU8 has been fully cured, it is very difficult to remove and doesn’t appear to dissolve in most solvents. Hence why you need to use piranha in this case. SU8 on your mask plate will have been exposed many times and possibly is very old (perhaps similar to curing). <br clear="all"><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><font face="georgia, serif" size="4" style="font-family:georgia,serif;color:rgb(0,0,0)">-- Demis </font><font face="georgia, serif" size="1" style="font-family:georgia,serif;color:rgb(0,0,0)">(<a href="https://wiki.nanotech.ucsb.edu/wiki/Demis_D._John" target="_blank" style="font-family:georgia,serif">contact info</a>)</font><div><i style="font-family:"times new roman",serif">Reminder</i><span style="font-family:"times new roman",serif">: The NanoFab has a </span><a href="https://wiki.nanotech.ucsb.edu/wiki/Frequently_Asked_Questions#Publications_acknowledging_the_Nanofab" style="font-family:"times new roman",serif" target="_blank">publications policy</a><font face="georgia, serif" size="4" style="font-family:georgia,serif;color:rgb(0,0,0)"><br></font></div></div></div></div></div><div><br></div><div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Fri, Feb 13, 2026 at 16:46 Robert Nidetz <<a href="mailto:nidetz@umich.edu">nidetz@umich.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="auto">Definitely try the developer first. If it has not been cross linked by the exposure then it will clean up easy. But if it’s been exposed, you’ll need piranha solution. </div><div dir="auto"><br></div><div dir="auto">To prevent sticking in the future, make sure your tweezers cannot leave an impression after the soft bake once the wafer has cooled to room temperature. If they leave an impression, you’ll need to soft bake more. </div><div dir="auto"><br></div><div dir="auto">Good luck!<br clear="all"><br clear="all"><div dir="auto"><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div dir="ltr">Robert Nidetz, PhD (he/him/his)</div><div>University of Michigan</div><div dir="ltr">LNF User Liaison and Domain Expert</div><div dir="ltr">1241 EECS Building</div><div dir="ltr"><a href="https://www.google.com/maps/search/1301+Beal+Ave+Ann+Arbor,+MI+48109?entry=gmail&source=g">1301 Beal Ave</a></div><div><a href="https://www.google.com/maps/search/1301+Beal+Ave+Ann+Arbor,+MI+48109?entry=gmail&source=g">Ann Arbor, MI 48109</a></div><div><a href="mailto:nidetz@umich.edu" target="_blank">nidetz@umich.edu</a><br></div><div>734.496.8065</div><div dir="ltr"><div>Book an appointment: <a href="https://calendly.com/nidetz" target="_blank">https://calendly.com/nidetz</a></div></div></div></div></div></div><div><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Feb 12, 2026 at 7:36 PM Phillip Bauer <<a href="mailto:Phillip.Bauer@formfactor.com" target="_blank">Phillip.Bauer@formfactor.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
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I am somewhat new to SU-8 working with Positive resists throughout my career. I agree with data sheets are just guideline, for processing. I saw a note from another University to run a 65 deg post bake after the 95 deg soft bake. My question is about mask
cleaning. Is Sulfuric/Peroxide (Piranha ~ 60-90C) really needed. I would think the PGMEA or PGMEA/Acetone followed by IPA would be an effective clean. Just wanted to poll the audience. </div>
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