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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Doesn’t always work we find, eventually some enterprising user will find a way to melt an Al ingot onto a cooled hearth which should in theory not happen. But I do agree if this is not an issue and
you can dedicate a pocket then this is the best method. Some electron beam gun cooling channel design and water flows will get you a lot farther then others in this respect.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">In the last year I spent some time personally trying to improve our standard long throw Al evaporation process. We use 40cc pockets and there is no choice but to use a crucible because multiple materials
use the pockets and ultimately it makes multi user/project operation easier. Al is cheap to refill, and the odd crucible is just noise in the tool budget too.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">What I found ultimately was that alumina was the best. Power to deposit was significantly lower than any other crucible for a given rate because due to the thermally insulating properties of Al2O3
the entire Al crucible load melts and becomes totally molten, this gives a very easy to control deposition with a large vapour emitting area and even with a 1m+ throw distance rates of 2-5A/s at the wafer were no trouble for ~1kW of input power. The downside
is that Al2O3 always cracks, no matter now gentle you are with preconditioning. But considering the overall budget of tool operation a new crucible every few months is not significant. The crucible outer wall stays cold and any Al that moves through the cracks
cools and does not transmit further – this gives the cracked crucible physical stability. Eventually after several months and many um of Al you see the power for a given deposition rate slowly start to increase. This is the cue that Al moving through cracks
has begun thermal contact with the pocket and is a sign to prepare to swap the crucible for a new one. Al in this crucible stays perfectly shiny following deposition for its entire lifetime.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">For graphite, coated graphite or fabmate the crucible will eventually crack, and the Al will react with the liner. The liners I tested like this gave a yellow-ish hue to the Al after only a few depositions
which I presume is C contamination (although I have not yet tested it via elemental analysis). The colour change is obvious by eye. Power vs Al2O3 is approximately double for a given rate due to increased thermal conduction through the crucible, and you cannot
melt the entire Al contents. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Using metallic crucibles such as W the Al will creep eventually ruining the deposition by demanding significantly more power required for a given rate as it goes over the top of the crucible, only
a small spot can be melted, and the power required is 2-3x more than Al2O3. Crucibles are physically unreactive and Al stays pure but it does not take long before creep renders them useless.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">So all in, if you must use a crucible for Al I would recommend Al2O3 or a similar thermally insulating unreactive material. And I would always take any material vendor suggestions with a pinch of
salt and just a starting point. Tool vendors I listen more closely too but seeing is always believing. Try the options yourself and draw your own conclusions based on expected theory. Al2O3 has been our standard crucible for over a year now and both research
and enterprise users of the tool are happy. Keep a pre melted 2<sup>nd</sup> crucible ready to go as needed and all is fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Owain. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> labnetwork <labnetwork-bounces@mtl.mit.edu>
<b>On Behalf Of </b>Steffen, Paul<br>
<b>Sent:</b> 29 August 2022 14:01<br>
<b>To:</b> 'Chandan H B' <chandanachar95@gmail.com>; labnetwork@mtl.mit.edu<br>
<b>Subject:</b> Re: [labnetwork] Regarding : Aluminium E-Beam Evaporation<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="line-height:16.5pt;background:#F7F9FA"><strong><span lang="EN-US" style="font-size:10.5pt;font-family:"Calibri",sans-serif;color:#8D3970">CAUTION:</span></strong><span lang="EN-US" style="font-size:10.5pt;color:#8D3970"> This e-mail
originated outside the University of Southampton. <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Chandan,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Don’t bother with the crucible liner. Just melt a big chunk of aluminum directly in the pocket. It will not adhere to the walls so you will be able to remove it if you need to swap materials.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>>
<b>On Behalf Of </b>Chandan H B<br>
<b>Sent:</b> Monday, August 29, 2022 2:04 AM<br>
<b>To:</b> <a href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a><br>
<b>Subject:</b> [labnetwork] Regarding : Aluminium E-Beam Evaporation<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span lang="EN-US" style="font-size:1.0pt;color:white">Dear Lab network community, We are currently facing an issue in the deposition of Aluminium in one of our Electron beam evaporation tools, we tried
intermetallic, fab mate, copper, glassy coated graphite, and graphite crucibles for the evaporation.
<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span lang="EN-US" style="font-size:1.0pt;color:white"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Dear Lab network community,<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">We are currently facing an issue in the deposition of Aluminium in one of our Electron beam evaporation tools, we tried intermetallic, fab mate, copper, glassy coated graphite, and graphite crucibles for the evaporation.
It seems that none of them are working out. <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">We see crucible gets broken at the initial deposition quite often.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Are we missing out on any parameters unchecked?<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Kindly recommend us a few parameters or solutions for the same.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Any suggestions/Inputs are highly appreciated.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Thanks in advance!<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">CHANDAN H B<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">THIN FILM ENGINEER<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">P.S: Here are a few parameters that are provided to the tool.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Power: 10KW<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Voltage: 10KV constant<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Current: Variable <o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Rise1 & Soak1: 5min & 1min /8min & 2min<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Rise1 Power: 4% (for intermetallic crucible)<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Rise2 & Soak2: 5min & 1min /8min & 2min<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Rise2 Power: 8% (for intermetallic crucible)<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Ramp down: 5min<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Rate of deposition: 0.1nm/sec<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Beam Pattern: Spot Beam at the center of the crucible<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Crucible Volume: 20cc<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Material fill %: As recommended 67-75%<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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