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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have seen this before in an ION Mill tool. If the resist profile is steep think step profile then the metal catches along the resist edge and makes a stringer, most of the time solved by a high temp hard bake to roll the resist over or
maybe you have some sputtering going on, what pressure it the etch at?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rick<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> <b>
On Behalf Of </b>Hollingshead, Dave<br>
<b>Sent:</b> Friday, April 29, 2022 3:23 PM<br>
<b>To:</b> labnetwork@mtl.mit.edu<br>
<b>Subject:</b> [labnetwork] Direct write + plasma etch residue<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Good afternoon everyone,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We have recently run into some very ‘interesting’ (completely perplexing) issues while trying to etch some III-V samples in our ICP. Essentially we are seeing some sort of residue on the protected regions of the devices after stripping
the resist. Whatever it is, the material seems to also be affecting our etch profiles. The odd part is that the residue has a clear directionality to it and in the present case only appears on two edges. This has led us to believe that is must in some way
be a result of some non-uniform / “angled” exposure from our MLA150. While I can completely understand differing etched sidewall slopes or skewed features if the resist sidewalls are not uniform on all sides, I am having difficulty understanding how this might
cause the residue we are seeing (especially in a positive resist). <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any thoughts or possible explanations would be greatly appreciated.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Attached are some microscope and SEM images of what we are seeing. I have plenty more I’d be happy to share with those that may be interested!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A few relevant processing notes:<o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">All etches were done using a BCl3/Ar chemistry in our Plasmatherm 770 system<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">~18-20 minutes of etch time, total depth of ~2.5-3.0µm<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">We have repeated these issues on InGaAs device samples as well as bulk GaAs test samples<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">Issue repeated with both SPR220 and S1827 resist masks (both were un-hardbaked, but this is also something we are going to look into)<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">Exposures seem to be properly dosed, but we are planning an etch test on a dose/defocus array to see if exposure has any effect<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">All resist removal was done in 80C NMP<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo3">We have attempted some follow-on O<sub>2</sub> plasma etches, that seem to remove the material, but it is very slow<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">-Dave<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#BB0000;background:white">Dave Hollingshead </span></b><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333"><br>
<span style="background:white">Manager of Research Operations – Nanotech West Lab<br>
<b>The Ohio State University</b></span><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333;background:white">Suite 100, 1381 Kinnear Road, Columbus, OH 43212</span><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333"><br>
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</span><span style="color:#333333"><a href="mailto:hollingshead.19@osu.edu"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:blue;background:white">hollingshead.19@osu.edu</span></a></span><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333;background:white"> </span><span style="color:#333333"><a href="http://osu.edu/"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:blue;background:white">osu.edu</span></a><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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