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<p>I agree with Noah Clay, he identifies the issues correctly, in my
view.</p>
<p>I would add that a general rule of thumb for liftoff is to spin
resist about 3X thicker than the metal layer you want to liftoff.</p>
<p>Regards,</p>
<p>Mark K Mondol <br>
</p>
<div class="moz-cite-prefix">On 1/4/2019 2:16 PM, Noah Clay wrote:<br>
</div>
<blockquote type="cite"
cite="mid:95E37FB5-C122-4884-893F-E242840A46E3@upenn.edu">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div class="moz-text-html" lang="x-unicode">Hello Adithi,
<div><br>
</div>
<div>As you know, ceramics can be quite porous and metal
adhesion can be diminished by surface/internally adsorbed
water, organics, etc. Therefore, you may consider deep solvent
cleaning, other surface treatments as appropriate (e.g.,
plasma) for your material and a lengthy dehydration bake prior
to resist application. If pre-resist cleaning proves
ineffective, then after resist development, you may consider
O2 plasma or, if available, in-situ ion bombardment. Lastly,
given the rough topography of your substrate, there may be
undeveloped or underexposed pockets of resist on the
substrate, which necessitate optimizing bake, exposure and
develop conditions.</div>
<div><br>
</div>
<div>As for HMDS (mainly used for Si), without knowing the type
of ceramic you’re using, I can’t say that it will be effective
as an adhesion promoter. I very humbly/respectfully disagree
with previous comments that HMDS is used mostly for etching,
but agree that<span style="background-color: rgba(255, 255,
255, 0);"> to facilitate liftoff, </span>a relatively thick
LOR layer should be spun and baked before application of
imaging resist.</div>
<div><br>
</div>
<div>Best,</div>
<div>Noah Clay</div>
<div><i><br>
</i></div>
<div><i>Singh Center for Nanotechnology </i></div>
<div><i>University of Pennsylvania </i></div>
<div><i>Philadelphia, PA</i><br>
<br>
<div id="AppleMailSignature" dir="ltr">Sent from my iPhone</div>
<div dir="ltr"><br>
On Jan 4, 2019, at 08:51, Hitesh Kamble <<a
href="mailto:hit.kamble@gmail.com" moz-do-not-send="true">hit.kamble@gmail.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="auto">Hello Adithi,
<div dir="auto"> In case of HMDS ,it will improve
adhesion but resists will not remove easily from
surafce.HMDS is mostly use in etching. Since you're
having rough surface, <span
style="font-family:sans-serif">Instead of HMDS use
LOR 3B or say liftOFF resists which helps to improve
liftoff process.</span></div>
<div dir="auto"><span style="font-family:sans-serif">Also
for 250nm metallization you need more than 2um thick
resists.</span></div>
<div dir="auto"><span style="font-family:sans-serif"><br>
</span></div>
<div dir="auto"><span style="font-family:sans-serif">We
did not do this on ceramic samples exactly but
successfully did liftoff on etched/textured glass
and etched samples(roughness more than~400nm).</span></div>
<div dir="auto"><span style="font-family:sans-serif">Following
are my suggestions:</span></div>
<div dir="auto"><span style="font-family:sans-serif">-Time
Interval between litho and deposition should be
lowest as possible</span></div>
<div dir="auto"><span style="font-family:sans-serif">-
Dehydration at higher temp and for longer time.</span></div>
<div dir="auto"><font face="sans-serif">-LOR 3B coating
at lower rpm and gradually increase rpm.</font></div>
<div dir="auto"><font face="sans-serif">-Keep sample in
Remover PG and heat at 80C for 5min or more if metal
not lifted,(Sonication not recquired in most cases)</font></div>
<div dir="auto"><br>
</div>
<div dir="auto"><br>
</div>
<div dir="auto"><font face="sans-serif">Thanks,</font></div>
<div dir="auto"><font face="sans-serif">Hitesh Kamble</font></div>
<div dir="auto"><font face="sans-serif">IITBNF-IIT
Bombay</font></div>
<div dir="auto"><span style="font-family:sans-serif"><br>
</span></div>
<br>
<br>
<div class="gmail_quote" dir="auto">
<div dir="ltr">On Fri 4 Jan, 2019, 6:08 PM ADITHI U
<<a href="mailto:uadithi@iisc.ac.in"
moz-do-not-send="true">uadithi@iisc.ac.in</a>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">
<div
id="m_-8304701522397863792divtagdefaultwrapper"
dir="ltr"
style="font-size:12pt;color:rgb(0,0,0);font-family:Calibri,Helvetica,sans-serif,EmojiFont,"Apple
Color Emoji","Segoe UI
Emoji",NotoColorEmoji,"Segoe UI
Symbol","Android
Emoji",EmojiSymbols">
<p style="margin-top:0;margin-bottom:0">Dear
All,</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0"> We
are having difficulties in doing metal(Ti/Pt)
lift off on ceramic substrates. Does any of
you have experience on fabricating metal
patterns on the rough Ceramic Substrates.
Below are the details of the process done.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0"> The
roughness of the ceramic substrates were
approximately 400nm. We had used HMDS as
adhesion promoter for lithography, the
thickness of the Photoresist was ~ 1.5um.The
thickness of the Ti/Pt layer was ~ 250nm.
Immediately after lithography the deposition
was done followed by 48 hours of lift
off(Acetone) process.
Ultrasonication(5-10mins) in Acetone was done
after 48hours. </p>
<div id="m_-8304701522397863792Signature">
<div
id="m_-8304701522397863792divtagdefaultwrapper"
dir="ltr"
style="font-size:12pt;color:rgb(0,0,0);font-family:Calibri,Helvetica,sans-serif,EmojiFont,"Apple
Color Emoji","Segoe UI
Emoji",NotoColorEmoji,"Segoe UI
Symbol","Android
Emoji",EmojiSymbols">
<p><span
id="m_-8304701522397863792ms-rterangepaste-start"></span></p>
<pre style="white-space:pre-wrap;font-size:9pt"><span style="font-size:9pt;font-family:"Arial Black",Arial,sans-serif"><font color="#ff0000"><span style="color:rgb(0,0,0)"><b><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small">Best Regards</span><span class="m_-8304701522397863792HOEnZb"><font color="#888888">
</font></span></b><span class="m_-8304701522397863792HOEnZb"><font color="#888888"><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small"><b>
Adithi.U
Senior Facility Technologist,
National Nano Fabrication Centre,
CeNSE, Indian Institute of Science
Bangalore</b></div></font></span></span></font></span></pre>
<span
id="m_-8304701522397863792ms-rterangepaste-end"></span><br>
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<pre class="moz-signature" cols="72">--
Mark K Mondol
Assistant Director NanoStructures Laboratory
And
Facility Manager
Scanning Electron Beam Lithography Facility
Bldg 36 Room 229
<a class="moz-txt-link-abbreviated" href="http://www.rle.mit.edu/sebl">www.rle.mit.edu/sebl</a>
<a class="moz-txt-link-abbreviated" href="mailto:mondol@mit.edu">mondol@mit.edu</a>
office - 617-253-9617
cell - 617-224-8756</pre>
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