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<p class="MsoNormal"><span style="color:#1F497D">Hi guys, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> We’ve been using both techniques at UofL, i.e. Teflon lined quartz tanks and 6” or 8” diameter beaker with reflux condenser. One advantage of the quartz tanks for many our users is having the space to use
a PEEK fixture for doing single sided etches. These fixtures protect both the wafer edge and the back side during the etch resulting in a very clean looking final product. Etches done with the fixture tend to produce a more robust wafer as one frequently
has oxide defects at the edge that results in nucleation sites for cracks upon further handling. This is also true for TMAH etches. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Michael Martin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Lab Grunt <o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="color:#1F497D"><o:p> </o:p></span></a></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> labnetwork-bounces@mtl.mit.edu [mailto:labnetwork-bounces@mtl.mit.edu]
<b>On Behalf Of </b>Luciani, Vincent<br>
<b>Sent:</b> Tuesday, July 23, 2013 9:02 AM<br>
<b>To:</b> 'Tony L Olsen'; labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] KOH Tank Design<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Hello Tony,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">This is an interesting question for me because I am considering changing strategies away from the built in tank.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">First:<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="color:#1F497D">The approach that Jeff describes has successfully worked for me over the years in a few different implementations including the one we have now ( by Reynolds’s Tech). I personally like the quartz or Teflon
lined quartz. I would stay away from a SS tank.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">However, there is dissatisfaction in my KOH etch community that has me re-evaluating our approach.
<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="color:#1F497D">Based on the comments and usage behavior of our users over the last few years, our KOH setup is not what they want. Having done extensive KOH etching experiments over the years, I agree and sympathize with some
of their specific complaints.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">Their issues (partial list):<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="color:#1F497D">I want to mix a custom version of KOH etch mixture. Don’t make me use your community tank.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I don’t need a large volume. So your dedicated tank is too big.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The built –in tank is too slow, takes too long to heat and cool thus limited user throughput.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Sometimes I wonder if tank contamination from a previous users botched experiment affected mine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I want to watch my sample etch. There are many reasons this can be a real need.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">And more!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">My Issue</span></b><span style="color:#1F497D">:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">They want to set up their own version for a day or two or at a time and we don’t have the space to allow folks to set up camp in a wet bench .<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">What I plan for next time:<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="color:#1F497D">One day when I replace our KOH bench I will make a bench with 3 or 4 stations, each of which have a big quartz beaker with water cooled reflux lid, thermometer (or TC) well, on a stirring hotplate with excellent
lighting and good visibility of the sample during the etch. This seems to be what most “advanced” KOH users want…at NIST anyway. Certainly, the built-in, heated tank is perfect for some labs. I want to poiuntb out that it is not always the case. We definitely
have more researchers/users that would like the multiple station, raised tank version I described.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Vince<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">Vincent K. Luciani<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">NanoFab Manager<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D"><a href="http://www.cnst.nist.gov/">Center for Nanoscale Science and Technology</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">National Institute of Standards and Technology<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">100 Bureau Drive, MS 6201<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">Gaithersburg, MD 20899-6200 USA<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Microsoft Sans Serif","sans-serif";color:#1F497D">+1-301-975-2886<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Minion Pro";color:#1F497D"><img border="0" width="397" height="76" id="Picture_x0020_1" src="cid:image001.jpg@01CE87AF.E74EC9D0" alt="Description: CNST Horztl Color logo"></span><span style="color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a> [<a href="mailto:labnetwork-bounces@mtl.mit.edu">mailto:labnetwork-bounces@mtl.mit.edu</a>]
<b>On Behalf Of </b>Tony L Olsen<br>
<b>Sent:</b> Monday, July 22, 2013 6:03 PM<br>
<b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> [labnetwork] KOH Tank Design<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Dear Labnetwork<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We are building a new wet bench and would like to include a dedicated KOH etch bath to replace the current methodology of glassware with stir bars on a hotplate. We generally use a bath of 80°C.<o:p></o:p></p>
<p class="MsoNormal">Our wetbench vendor initially quoted a recirculated bath in a stainless steel tank. We are concerned about the stainless, nor do we believe the Teflon or PVDF wetted surfaces in the proposed diaphragm pump will hold up to the hot KOH.
Another option we are aware of is a quartz tank heated externally by recirculated water. I’m certain there are other options, too.<o:p></o:p></p>
<p class="MsoNormal">Can you share your experience with dedicated KOH baths? What is the configuration? What are the materials? How do you mix/stir the bath? What problems have you experienced? What would you do next time?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank You,<o:p></o:p></p>
<p class="MsoNormal">tonyO<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tony Olsen<o:p></o:p></p>
<p class="MsoNormal">Nanofab Cleanroom Supervisor/Process Engineer<o:p></o:p></p>
<p class="MsoNormal">36 S Wasatch Dr, Suite 2500 SMBB<o:p></o:p></p>
<p class="MsoNormal">Salt Lake City, UT 84112<o:p></o:p></p>
<p class="MsoNormal">801-587-0651 office<o:p></o:p></p>
<p class="MsoNormal">801-587-3077 fax<o:p></o:p></p>
<p class="MsoNormal"><a href="http://www.nanofab.utah.edu/"><span style="color:#6666CC">www.nanofab.utah.edu</span></a><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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