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    <p>Hi Joe,</p>
    <p>Adding Glycerin to an HF solution will reduce the Al etching or
      even inhibit it. I learned about this many years ago and do not
      have the references handy.  But by a quick search I found this:</p>
    <p><a class="moz-txt-link-freetext" href="https://gnusha.org/~nmz787/mems/unorganized/wet_etch.pdf">https://gnusha.org/~nmz787/mems/unorganized/wet_etch.pdf</a></p>
    <p>Good luck,</p>
    <p>Alireza Mesgar</p>
    <p>Equipment Engineer<br>
      Texas Instruments<br>
    </p>
    <p> <br>
    </p>
    <div class="moz-cite-prefix">On 10/26/21 15:48, Maduzia, Joseph
      Walter wrote:<br>
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cite="mid:DM6PR11MB41054D2F449DF329673D3093ED849@DM6PR11MB4105.namprd11.prod.outlook.com">
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        <p class="MsoNormal">Hello,<o:p></o:p></p>
        <p class="MsoNormal"><o:p> </o:p></p>
        <p class="MsoNormal">Does anyone have any suggestions for mask
          materials to protect Al in HF 49% for SiO2 removal in SOI
          wafer? The device is SOI, ICP DRIE etched to glass, HF etch to
          undercut and free devices, but have Al contact pads and AL is
          dep’d first. Typically we use PR as pattern mask, but the Al
          is etching behind the PR. In this case the Al is deposited
          first, so although order of operations change might help, it’s
          not a good option atm.<o:p></o:p></p>
        <p class="MsoNormal"><br>
          Thank you for any suggestions you might have!<o:p></o:p></p>
        <p class="MsoNormal"><b><span
              style="color:#13294B;text-transform:uppercase">JOE MADUZIA</span></b><span
            style="color:black"><br>
          </span><i><span style="color:#13294B">MNMS Laboratory
              Specialist</span></i><span style="color:black"><br>
             <br>
          </span><span style="color:#13294B">The Grainger College of
            Engineering</span><span style="color:black"><br>
          </span><span style="color:#13294B">Mechanical Science and
            Engineering</span><span style="color:black"><br>
            <br>
          </span><span style="color:#13294B">2239 Sidney Lu Mechanical
            Engineering Bldg</span><span style="color:black"><br>
          </span><span style="color:#13294B">1206 W. Green</span><span
            style="color:black"><br>
          </span><span style="color:#13294B">Urbana, IL 61801</span><span
            style="color:black"><br>
          </span><span style="color:#13294B">217.244.6302 | </span><a
            href="mailto:jmaduzi2@illinois.edu" moz-do-not-send="true"><span
              style="color:#0563C1">jmaduzi2@illinois.edu</span></a><o:p></o:p></p>
        <p class="MsoNormal"><a
            href="https://cleanroom.mechse.illinois.edu/"
            moz-do-not-send="true"><span style="color:#0563C1">https://cleanroom.mechse.illinois.edu/</span></a><span
            style="color:black"><br>
             <br>
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            <br>
          </span><i><span style="color:#666666">Under the Illinois
              Freedom of Information Act any written communication to or
              from university employees regarding university business is
              a public record and may be subject to public disclosure.</span></i><o:p></o:p></p>
        <p class="MsoNormal"><o:p> </o:p></p>
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      <pre class="moz-quote-pre" wrap="">_______________________________________________
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