<div><div><div dir="auto">Perhaps try a higher dep rate - the theory being that heating (from optical/other emission) is causing the PMMA to outgas, and long slow deps may cause more heating. </div><div dir="auto">Eg. Keep the Au dep to <1min total (you may need to adjust the soak steps w/ shutter closed so it opens the shutter with ~0.5Å/sec and fairly fast feedback loop).</div><div dir="auto"><br></div><div dir="auto">Also, measure the thin-film stress of your Au - maybe it is high, causing/exacerbating delamination. </div><div dir="auto">However since your image also shows exploded bubbles on the PMMA only, I suspect outgassing/bubbles more than just regular delamination due to stress. </div><div dir="auto"><br clear="all"><div dir="auto"><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" style="font-family:georgia,serif" target="_blank">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></div><div><div><div><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jul 22, 2025 at 07:23 Philipp Altpeter <<a href="mailto:philipp.altpeter@lmu.de" target="_blank">philipp.altpeter@lmu.de</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)"><u></u>
<div>
<p>Dear all,</p>
<p>In recent months, we installed a
new UHV e-beam evaporator and have since encountered significant
issues with our standard lift-off process using 3 nm Chromium
followed by 50 nm Gold. Specifically, we are observing the
formation of large bubbles beneath the PMMA, which severely damage
the PMMA layer (see image below). The rate is decently low, 0.6
A/s at around 40mA emission current, 10 kV. After around 30 nm of
thickness, bubbles become clearly visible.</p>
<p>Interestingly, deposition on bare
silicon, silicon dioxide, or other (photo)resists appears to
proceed without problems.</p>
<p>We have already tried adjusting
various parameters — including cooling conditions, beam wobbling,
throw distance, and acceleration voltage. We also modified the
PMMA baking protocol and tested PMMA dissolved in different
solvents — all without success.</p>
<p>If anyone has experienced
similar issues or has suggestions for troubleshooting, your input
would be greatly appreciated.</p>
<p>Thank you in advance for your
help!</p>
<p>Best regards,<br>
Philipp</p>
<p><br>
</p>
<p><img src="cid:ii_1983289494fa181d80a1" alt="" style="width:526px;max-width:100%"></p>
<pre cols="72" style="font-family:monospace">--
Philipp Altpeter
Fakultät für Physik der LMU
LS Prof. Efetov
<a href="https://www.google.com/maps/search/Geschwister-Scholl-Platz+1%0D%0AD-80539+M%C3%BCnchen?entry=gmail&source=g" style="font-family:monospace" target="_blank">Geschwister-Scholl-Platz 1
D-80539 München</a>
T. +49 (0)89 2180-3733</pre>
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