<div dir="auto">Instead of Piranha, we have a heated bath of PureStrip. From the MSDS:</div><div dir="auto"><div><img src="cid:ii_1956e3a7c60139041f11" style="max-width: 100%;"></div><div dir="auto"><br></div>Users heat the bath to 60°C when they want to use it, then cool it down when they’re done. This is because the datasheet and our experience finds that keeping it at 60°C for >>24hrs makes it lose its potency. </div><div dir="auto">Once in a while we have to refill the bath if we find (via SEM!) that PR residues were not removed as expected. </div><div dir="auto"><br></div><div dir="auto">We used to use Nanostrip instead, which basically never had this problem and we rarely refilled. I believe that the mfg stopped providing that and recommended PureStrip. <br clear="all"><br clear="all"><div dir="auto"><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><font face="georgia, serif" size="4" style="font-family:georgia,serif;color:rgb(0,0,0)">-- Demis </font><font face="georgia, serif" size="1" style="font-family:georgia,serif;color:rgb(0,0,0)">(<a href="https://wiki.nanotech.ucsb.edu/wiki/Demis_D._John" target="_blank" style="font-family:georgia,serif">contact info</a>)</font><div><i style="font-family:"times new roman",serif">Reminder</i><span style="font-family:"times new roman",serif">: The NanoFab has a </span><a href="https://wiki.nanotech.ucsb.edu/wiki/Frequently_Asked_Questions#Publications_acknowledging_the_Nanofab" style="font-family:"times new roman",serif" target="_blank">publications policy</a><font face="georgia, serif" size="4" style="font-family:georgia,serif;color:rgb(0,0,0)"><br></font></div></div></div></div></div><div><br></div><div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Thu, Mar 6, 2025 at 16:59 Hope Fa-Kaji <<a href="mailto:hfakaji@lbl.gov">hfakaji@lbl.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="ltr"><div>Hi Robert,</div><div><br></div><div>This is an anecdotal answer based on my experience in industry.</div><div><br></div><div>Bath life and spiking limits will depend greatly on the application for which you are using SPM. When H2SO4 and H2O2 react to form Caro's acid, the other liquid byproduct is H2O. As the H2O concentration of the bath increases, all cleans and etches become less effective.</div><div><br></div><div>If you are using the SPM for bulk photoresist removal (i.e. your "dirty" SPM), I'd think the bath life limitation is driven much more by the particulate count than the spiking. Also, I assume in this case you have a much higher H2O2:H2SO4 ratio and are consuming H2SO4 much more quickly.</div><div><br></div><div>For other applications like targeted etching or simple cleans, you should have more room to do more spiking. In particular, if you don't have a constant flow of wafers to process, I would consider pre-batch spiking instead of a time based interval. This ensures there is enough H2O2 present to react and form Caro's acid. Otherwise, the H2O2 could be consumed and/or evaporate before the wafers enter the bath.</div><div><br></div><div>In my previous role (300mm wafer tools with inline filter/heater/pump and lid covers to minimize evaporation), we ran some studies on H2O2 spiking and could get 30 batches out of one bath (run at 120C) before the measured H2SO4 concentration went below 88%. We had previously run to 15 batches but we increased the limit by increasing the batch limit and running numerous particle wafer tests to demonstrate no decline in bath quality.</div><div><br></div>I hope this helps!</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Mar 6, 2025 at 2:22 PM Macdonald, Robert (GE Aerospace, US) <<a href="mailto:robert.macdonald@geaerospace.com" target="_blank">robert.macdonald@geaerospace.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div>
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<p class="MsoNormal">Wondering who is operating SPM baths (Sulphuric Peroxide Mixture).<u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">We heat Sulphuric to 120C (in a quartz bath), and spike with H2O2, at 1% by volume.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">We are doing 10 spikes, or 1 week, then dispose/aspirate (the cooled) bath, whichever comes first.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt">Does anyone here have opinions or data on the number of spikes they allow?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt"><u></u> <u></u></span></p>
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</div></blockquote></div><div><br clear="all"></div><br><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><b><span style="font-family:georgia,serif">All the best,</span></b></div><div><span style="font-family:georgia,serif"><br></span></div><div><span style="font-family:georgia,serif">Hope Fa-Kaji</span></div><div><span style="font-family:georgia,serif;color:rgb(102,102,102)">Semiconductor Equipment Engineer</span></div><div><span style="font-family:georgia,serif;color:rgb(102,102,102)">Microsystems Laboratory</span></div><div><span style="font-family:georgia,serif;color:rgb(102,102,102)"><img width="420" height="95" src="https://ci3.googleusercontent.com/mail-sig/AIorK4yBx1QCkq_DPrtgR5B_lqZ1t-Y52u9Nq4qfhFi5qkDXBdbcb8OmcM5Is87_HYBHrwehwut24-Put5a8" style="font-family: georgia, serif;"><br></span></div><div><span style="font-family:georgia,serif"></span></div><div></div></div></div>
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