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<p data-start="221" data-end="230">Dear all,</p>
<p data-start="232" data-end="545">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 data-start="547" data-end="667">Interestingly, deposition on bare
silicon, silicon dioxide, or other (photo)resists appears to
proceed without problems.</p>
<p data-start="669" data-end="927">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 data-start="929" data-end="1050">If anyone has experienced
similar issues or has suggestions for troubleshooting, your input
would be greatly appreciated.</p>
<p data-start="1052" data-end="1087">Thank you in advance for your
help!</p>
<p data-start="1089" data-end="1112">Best regards,<br
data-start="1102" data-end="1105">
Philipp</p>
<p><br>
</p>
<p><img src="cid:part1.GTwErJ1B.LxA87e0N@lmu.de" alt=""></p>
<pre class="moz-signature" cols="72">--
Philipp Altpeter
Fakultät für Physik der LMU
LS Prof. Efetov
Geschwister-Scholl-Platz 1
D-80539 München
T. +49 (0)89 2180-3733</pre>
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