<div dir="ltr">Dear Aditi,<div><br></div><div>Are you observing undercut in your resist profile before you put metal. Without sufficient undercut [~ 1um] lift off would be challenging regardless of other issues. </div><div><br></div><div>The total resist stack should be > 3X the metal you intend to deposit. If you are using LOR, the LOR thx should be > 1.4 times the metal thickness. Bilayer lithography [LOR + Imaging], is little better option for lift off, [however you can still do with single layer provided you have undercut]. The imaging resist to LOR thickness ratio is usually 3:1 or 4:1. I observed it to be a little more challenging in process with ratio of 1:1 or 1:2 as advertised in the LOR datasheets.</div><div><br></div><div>Thanks,</div><div>Kamal</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Jan 4, 2019 at 7:52 PM Mark K Mondol <<a href="mailto:mondol@mit.edu">mondol@mit.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
  
    
  
  <div bgcolor="#FFFFFF">
    <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="gmail-m_3904853039364512131moz-cite-prefix">On 1/4/2019 2:16 PM, Noah Clay wrote:<br>
    </div>
    <blockquote type="cite">
      
      <div class="gmail-m_3904853039364512131moz-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="gmail-m_3904853039364512131AppleMailSignature" 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" target="_blank">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" target="_blank">uadithi@iisc.ac.in</a>
                    wrote:<br>
                  </div>
                  <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
                    <div dir="ltr">
                      <div id="gmail-m_3904853039364512131m_-8304701522397863792divtagdefaultwrapper" dir="ltr">
                        <p style="margin-top:0px;margin-bottom:0px">Dear
                          All,</p>
                        <p style="margin-top:0px;margin-bottom:0px"><br>
                        </p>
                        <p style="margin-top:0px;margin-bottom:0px">      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:0px;margin-bottom:0px"><br>
                        </p>
                        <p style="margin-top:0px;margin-bottom:0px">   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="gmail-m_3904853039364512131m_-8304701522397863792Signature">
                          <div id="gmail-m_3904853039364512131m_-8304701522397863792divtagdefaultwrapper" dir="ltr">
                            <p><span id="gmail-m_3904853039364512131m_-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="gmail-m_3904853039364512131m_-8304701522397863792HOEnZb"><font color="#888888">
</font></span></b><span class="gmail-m_3904853039364512131m_-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="gmail-m_3904853039364512131m_-8304701522397863792ms-rterangepaste-end"></span><br>
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    <pre class="gmail-m_3904853039364512131moz-signature" cols="72">-- 
Mark K Mondol
Assistant Director NanoStructures Laboratory
And
Facility Manager
Scanning Electron Beam Lithography Facility
Bldg 36  Room 229
<a class="gmail-m_3904853039364512131moz-txt-link-abbreviated" href="http://www.rle.mit.edu/sebl" target="_blank">www.rle.mit.edu/sebl</a>
<a class="gmail-m_3904853039364512131moz-txt-link-abbreviated" href="mailto:mondol@mit.edu" target="_blank">mondol@mit.edu</a>
office - 617-253-9617
cell - 617-224-8756</pre>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Thanks,<br></div><div>Kamal </div><div><br></div></div></div></div></div></div></div></div>