<div dir="auto">Hi Dave,</div><div dir="auto"><br></div><div dir="auto">A couple of remarks:</div><div dir="auto">1- A Cl2-based chemistry react with resist materials and form a kind of a compound that is very hard to remove in classic ways, even an O2-ashing may not be helpful. I usually avoid using resist mask to etch III-V materials and instead I use a hard mask like SiNx or SiOx (PECVD deposited) as a mask, pattern it with a resist mask in a F-based chemistry), strip the resist before going to the Cl2-based ICP RIE etch. After the etch the remaining hard mask can be removed in BHF or a diluted HF</div><div dir="auto">2- what is the wafer temperature during etch? In does require T>150C to get the etching product InCl3 volatile. Not doing so will result in micro-masking (check a paper I published in 2014). </div><div dir="auto"><br></div><div dir="auto">Happy to discuss further details (offline) if you wish.</div><div dir="auto"><br></div><div dir="auto">Fouad Karouta </div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 29 Apr 2022 at 9:39 pm, Hollingshead, Dave <<a href="mailto:hollingshead.19@osu.edu">hollingshead.19@osu.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div lang="EN-US" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="m_3701621227993744503WordSection1">
<p class="MsoNormal">Good afternoon everyone,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></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). <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Any thoughts or possible explanations would be greatly appreciated.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></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!<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">A few relevant processing notes:<u></u><u></u></p>
<ul style="margin-top:0in" type="disc">
<li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">All etches were done using a BCl3/Ar chemistry in our Plasmatherm 770 system<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">~18-20 minutes of etch time, total depth of ~2.5-3.0µm<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">We have repeated these issues on InGaAs device samples as well as bulk GaAs test samples<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">Issue repeated with both SPR220 and S1827 resist masks (both were un-hardbaked, but this is also something we are going to look into)<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">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<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">All resist removal was done in 80C NMP<u></u><u></u></li><li class="m_3701621227993744503MsoListParagraph" style="margin-left:0in">We have attempted some follow-on O<sub>2</sub> plasma etches, that seem to remove the material, but it is very slow<u></u><u></u></li></ul>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks,<u></u><u></u></p>
<p class="MsoNormal">-Dave<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></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><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333;background:white">Suite 100, <a href="https://www.google.com/maps/search/1381+Kinnear+Road,+Columbus,+OH+43212?entry=gmail&source=g">1381 Kinnear Road, Columbus, OH 43212</a></span><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:#333333"><br>
<span style="background:white">614.292.1355 Office</span><br>
</span><span style="color:#333333"><a href="mailto:hollingshead.19@osu.edu" target="_blank"><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/" target="_blank"><span style="font-size:9.0pt;font-family:"Arial",sans-serif;color:blue;background:white">osu.edu</span></a></span><span style="color:#333333"><u></u><u></u></span></p>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
</div>
_______________________________________________<br>
labnetwork mailing list<br>
<a href="mailto:labnetwork@mtl.mit.edu" target="_blank">labnetwork@mtl.mit.edu</a><br>
<a href="https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork" rel="noreferrer" target="_blank">https://mtl.mit.edu/mailman/listinfo.cgi/labnetwork</a><br>
</blockquote></div></div>