<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"><meta name="Generator" content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-style-priority:99;
margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Hi Mcolisi,</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Given the set of materials you current de</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">posit in the tool</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">, there is a concern. Both Au and </span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Pt can form a brittle, high resistance intermetallic compound with Al, especially under heat. In the case of Au, it even has the nickname “purple plague,” due to it’s characteristic purple color. Because of the brittle nature of these compounds we have found that use of Al and Au or Al and Pt in a system together can result in flaking and potenial contamination if not managed properly. In particular, we have seen “purple plague” form on shields, holders, etc. when users evaporate Au and Al back to back. This may not initially contaminate the pockets or samples, but it can lead to premature flaking of materials in the chamber between maintenance cycles. In turn, the flakes can then potentially contaminate pockets of material. </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">All of the above said, I do believe it can be managed. In our case, we have enough requests to do Al and Au in the same chamber that we have decided to adapt and allow it. Our solution has been to deposit Ti before and after any Al run. This has helped to mitigate the issues, but I still suggest checking and cleaning shields, holders, etc. regularly. </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Best Regards,<br><br>Matt</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">--</span></p><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Matthew T. Moneck, Ph.D</span></b></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Executive Director, Claire & John Bertucci Nanotechnology Laboratory</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Electrical & Computer Engineering | Carnegie Mellon University</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">5000 Forbes Avenue, Pittsburgh, PA 15213-3890</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d">Phone: 412-268-5430</span></p><p class="MsoNormal"><a href="http://www.ece.cmu.edu/"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#0563c1">ece.cmu.edu</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><p class="MsoNormal"><a href="http://www.nanofab.ece.cmu.edu/"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#0563c1">nanofab.ece.cmu.edu</span></a><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p></div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1f497d"> </span></p><div><div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>> <b>On Behalf Of </b>Mcolisi Dlamini<br><b>Sent:</b> Tuesday, November 22, 2022 7:01 PM<br><b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br><b>Subject:</b> [labnetwork] Aluminum contamination concerns in PVD</span></p></div></div><p class="MsoNormal"> </p><div id="divtagdefaultwrapper"><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Dear lab network:</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">We are wondering if there are any contamination issues (or potential contamination) from adding and evaporating aluminum in our PVD system. We understand that there will be physical contamination from flakes and metal buildup. However, we are not sure whether Al will contaminate and affect other deposition processes. Our PVD is non-CMOS clean grade and is currently qualified to evaporate Au, Ti, Pd, and Pt on the e-beam hearth and only Cr has been used so far on the thermal source.</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">The key question we have is whether aluminum has a risk of contaminating the tool and affecting other processes? Our PVD is used for basic metallization needs including for lift-off and IC chip fabrication. </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">We reviewed previous exchanges on this network but they mostly focused on gold contamination in vacuum systems. Notably they do emphasize that tools should be classified based on cleanliness, eg. CMOS clean, semi-clean and the Au friendly category. This is something we will definitely keep in mind moving forward. (Gold contamination lab network thread: </span><a href="https://mtl.mit.edu/pipermail/labnetwork/2015-June/001867.html" target="_blank" title="https://mtl.mit.edu/pipermail/labnetwork/2015-June/001867.html
Ctrl+Click or tap to follow the link" id="LPlnk476711"><span style="font-size:11.0pt;font-family:"Arial",sans-serif">https://mtl.mit.edu/pipermail/labnetwork/2015-June/001867.html</span></a><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">). Additionally, there is mention of Aluminum carbide contamination when Al is evaporated via e-beam, but we gathered that this can be mitigated by evaporating at relatively low powers.</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">We will appreciate your insights on this topic specific to Al contamination as well as contamination in metal evaporators in general.</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">Thank you,</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal" style="background:white"><span style="font-size:11.0pt;font-family:"Arial",sans-serif;color:black">-Mcolisi</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span></p><p><span style="font-family:"Calibri",sans-serif;color:black"> </span></p><div id="Signature"><div id="divtagdefaultwrapper"><p><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#757b80">Mcolisi Dlamini</span></b><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p><a href="http://www.4dlabs.ca" id="LPNoLP"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#757b80">4D LABS</span></a><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#757b80">Simon Fraser University</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p><p><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#757b80">P: 778.782.9322</span><span style="font-family:"Calibri",sans-serif;color:black"></span></p></div></div></div></div></body></html>