[labnetwork] [Non-DoD Source] Re: question about Liner for Ni Ebeam Evaporation

Fri Dec 13 20:05:16 EST 2024

If you're manually controlling your beam current and watching the deposition, you aren't likely to burn through the hearth.  If you control with an automated recipe that increases the current when deposition rate drops (like when your run out of metal) it's a little more concerning. But you can usually set an upper limit on your current in the recipe.

-Cliff

Cliff Knollenberg

Processing Engineer - Lithography

Stanford Nanofabrication Facility

650-721-1274

[Image]

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From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Ryan Rivers <rrivers at berkeley.edu>
Sent: Friday, December 13, 2024 3:36 PM
To: Martin, Michael <michael.martin at louisville.edu>
Cc: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] [Non-DoD Source] Re: question about Liner for Ni Ebeam Evaporation

I generally avoid hitting the whole list with a response, but spacers have been so wildly successful at UC Berkeley that I feel obligated to express good confidence in the method:

The primary difficulty with most of the materials discussed in this thread is that most 2.2cc crucibles have thin walls and do not take to thermal shock very well. The crucible liner itself has low mass and often a low thermal mass (Specific heat * mass). A molten metal drastically increases the thermal mass of the liner wherever it has good contact. If you miss with your e-beam you can easily hit the crucible liner wall directly, and doing so will create a hot spot. Generating a hot spot while having your crucible cooled on all sides will cause massive thermal gradients across the crucible wherever you do *not* have conformal contact of metal inside the crucible. If you have a cup-shaped crucible with a 300C+ thermal gradient across a 1cm space, it's going to shatter from internal stress in most ceramic materials. Often, it will shatter with enough force to eject pieces from the pocket. That includes graphite, Al2O3, or most other materials. Copper liners won't do that but they introduce other alloying problems that can be a pain to deal with.

We use spacers in all of our evaporators at the UC Berkeley NanoLab. Spacing your ceramic liner off the floor of your hearth or pocket allows you to use smaller beam currents to get the same temperature (effectively, evaporation dep rate). Removing the sidewall of the liner from cooling contact ensures that the cooling contact to the liner is always on a surface in good contact with molten thermal mass during operation, because liquid metal pools at the bottom of the liner. That outright prevents almost all forms of cracking. We routinely do nickel, titanium, aluminum, iron, and many more in FABMATE coated graphite. (Fabmate is a silicon coating that just keeps the graphite dust down dramatically). Anything FABMATE can't handle (e.g., Silver, Gold due to various material incompatibilities and "Wierd stuff" that can happen.) Tungsten usually can, especially if you coat it in ZrO2. We've got a very healthy evaporation usage in the lab, and I haven't had a graphite crucible shatter since 2014 when we implemented spacers.

One last note - 2.2 cc tools are incredibly sensitive to beam focus. (Deformed e-beams can overheat the top edge of your liner and shatter it) Almost all research labs will tolerate a level of buildup on your focus pole pieces that is unhealthy for a 2.2cc e-beam tool. Removing and cleaning those pieces every couple months helps a ton. Also making sure that there's no dust that worked its way under the pole pieces and air-gapping your magnetic fields.

Hope this helps.

-Ryan

On Fri, Dec 13, 2024 at 1:13 PM Martin, Michael <michael.martin at louisville.edu<mailto:michael.martin at louisville.edu>> wrote:
LOL, TY for that info Michael.  I guess that will be our new M.O. for aluminum then.
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Subject: Re: [labnetwork] [Non-DoD Source] Re: question about Liner for Ni Ebeam Evaporation

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For whatever reason, Aluminum doesn't wet copper when molten in the hearth. Evaporation temperature is above Cu melting point, but still that's what I see.  There may still be some Cu diffusion -  but I saw no damage to hearth after a few  depositions (disclaimer - I am not a fan of direct loading)
Also, I tried real hard - although nonintentionally and fortunately unsuccessfully! - to burn a hole in a copper hearth. It's much harder than you think, I could only put a small dent in there.   That is a huge chunk of highly heat conductive copper that is water-cooled from the back. Makes me really wonder if there is actually liquid Al(or Ni) in contact with the copper at any point in the process, or liquid from above comes into contact with Cu and crystallizes right there. Certainly direct load would require higher beam power because of those things, with all associated effects like more outgassing and sample heating.

On a separate note, there was a similar discussion about Al a year or two ago. The best idea I saw is exactly opposite to direct load - it was about  using graphite spacer under Fabmate crucible to prevent heat contact of crucible walls and Cu hearth. Intermetallic crucibles are a second option.
Makes me wonder if spacer is worth trying with Ni.

Just my $0.02

Mike

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Michael Yakimov

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From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> on behalf of Martin, Michael <michael.martin at louisville.edu<mailto:michael.martin at louisville.edu>>
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To: EDWARDS, JASON R CTR USAF AFMC AFRL/RYDD <jason.edwards.30.ctr at us.af.mil<mailto:jason.edwards.30.ctr at us.af.mil>>; Beaudoin, Mario <beaudoin at physics.ubc.ca<mailto:beaudoin at physics.ubc.ca>>; Graham Gibson <gibsong at queensu.ca<mailto:gibsong at queensu.ca>>; Owain Clark <odc1n08 at soton.ac.uk<mailto:odc1n08 at soton.ac.uk>>; shokoofe haghighi <shokoofe_haghighi at yahoo.com<mailto:shokoofe_haghighi at yahoo.com>>; labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu> <labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>>
Subject: Re: [labnetwork] [Non-DoD Source] Re: question about Liner for Ni Ebeam Evaporation

Personally, I'm terrified that without a liner we will punch a hole in the pocket.  This would be catastrophic since then coolant would spray into the chamber just a couple of cm away from both high voltage and high current electrodes.

Jason (and others who go liner-less), wouldn't you be concerned about alloying the target material to the copper liner, I guess not?  We have issues similar to Ni with aluminum.  Almost every liner material seems incompatible with Al in one way or another yet ebeam Al can be very low stress. BTW, I believe lesker suggests to use thermal evaporation for Al.  However, if you just put the Al in the pocket without a liner I would expect a copper-aluminum alloy to form. Didn't Al-ebeam come up not so long ago in this group with several mentioning they put the material directly in the pocket?
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Subject: Re: [labnetwork] [Non-DoD Source] Re: question about Liner for Ni Ebeam Evaporation

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We evaporate straight out of the pocket for most of our metals, it’s interesting to hear that this may not be standard procedure for most labs. Not to draw attention away from the original question in this thread but I would like to hear more about what benefits you are getting from using liners. Is it just for ease of swapping metals in the pockets? In the instance of a Cu liner for Ni are you able to make a proper melt slug with the Ni considering you are unable to get the beam too close to the Cu liner? Thanks in advance.

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From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Beaudoin, Mario
Sent: Wednesday, December 11, 2024 5:07 PM
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Subject: [Non-DoD Source] Re: [labnetwork] question about Liner for Ni Ebeam Evaporation

We use a Cu crucible (4.4cc in a 7cc pocket) with good results.

Mario

On 2024-12-11 9:11 a.m., Graham Gibson wrote:

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   It’s interesting to see such a wide variety of experiences. I’m too chicken to evaporate right out of the pocket, so we went through a lot of liners, too, before settling on something.

   We have had good luck with Cu liners for Ni e-beam evaporation, but with a 2.2 cc pocket, we have to be very careful to keep the beam away from the walls and limit the deposition rate to 1 Angstrom/s.

  Hope you find something that works, liners get expensive!

Graham Gibson

Operations Manager, NanoFabrication Kingston

Queen’s University

945 Princess Street

Kingston, Ontario, Canada

K7L 0E9

gibsong at queensu.ca<mailto:gibsong at queensu.ca>

www.nanofabkingston.ca<http://www.nanofabkingston.ca/>

From: labnetwork <labnetwork-bounces at mtl.mit.edu><mailto:labnetwork-bounces at mtl.mit.edu> On Behalf Of Owain Clark
Sent: December 5, 2024 3:48 AM
To: Jeff Salzmann <jks7 at buffalo.edu><mailto:jks7 at buffalo.edu>; Bernhard Reineke <bernhard.reineke at uni-paderborn.de><mailto:bernhard.reineke at uni-paderborn.de>; shokoofe haghighi <shokoofe_haghighi at yahoo.com><mailto:shokoofe_haghighi at yahoo.com>; labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] question about Liner for Ni Ebeam Evaporation

Interestingly we have no trouble with Ni, it is one of our most stable materials and the crucible has not been changed in years. I believe it is W.

I suspect reading these comments it is because we have larger 40cc crucibles and we only melt a spot in the center with a small beam deflection. The crucible walls never see melted Ni.

BR, Owain

From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Jeff Salzmann
Sent: 04 December 2024 17:15
To: Bernhard Reineke <bernhard.reineke at uni-paderborn.de<mailto:bernhard.reineke at uni-paderborn.de>>; shokoofe haghighi <shokoofe_haghighi at yahoo.com<mailto:shokoofe_haghighi at yahoo.com>>; labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] question about Liner for Ni Ebeam Evaporation

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Haghighi,

This is my collection of failed crucibles used to evaporate Ni.

We decided on graphite, because copper was worse. We limit our deposition rate to 0.2 Å/sec to help extend the lifespan of the crucibles. They still fail after 2-3 depositions.

Regards,

Jeff

Jeff Salzmann

Assistant Professor of Research

Cleanroom Manager, Shared Instrumentation Laboratories

School of Engineering and Applied Sciences

University at Buffalo

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Buffalo, NY 14260

Tel: 716.645.2584

From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> on behalf of Bernhard Reineke <bernhard.reineke at uni-paderborn.de<mailto:bernhard.reineke at uni-paderborn.de>>
Date: Wednesday, December 4, 2024 at 11:46
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Subject: Re: [labnetwork] question about Liner for Ni Ebeam Evaporation

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Hi Haghighi,

we tried this once, same result. All liners will crack. Lesker has some recommendations on Ebeam evaporation of Ni: slow power ramp up and down (works well to prevent cracking for ~2-4 Runs, with fabmate). A Cu liner should work better but we never tested that.

https://www.lesker.com/newweb/deposition_materials/depositionmaterials_evaporationmaterials_1.cfm?pgid=ni1

Best,

Bernhard

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Von: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> im Auftrag von shokoofe haghighi <shokoofe_haghighi at yahoo.com<mailto:shokoofe_haghighi at yahoo.com>>
Gesendet: Mittwoch, 4. Dezember 2024 10:35:19
An: labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Betreff: [labnetwork] question about Liner for Ni Ebeam Evaporation

Hi, hope you are having good days,

this is Haghighi, working on metallization by a PVD, using thermal and Ebeam evaporation.

I have some issues choosing the right liner for Ni Ebeam evaporating, hope you find time to guide me through it.

We have tested graphite, glassy carbon coated graphite, Al2O3, Mo, W and Cu liners so far.

    Graphite liner just broke after first run from the border line of Ni surface. Glassy carbon coated graphite was more or less the same,

    Al2O3 endured for 4-5 runs before breaking but there were cracks on it,

    Mo liner totally melted and some kind of alloy was produced,

    W and Cu endured but their internal walls were some how melted and we can't be sure about pureness of evaporated Ni and final produced thin films.

do you have any other suggestions?

high voltage: 6.1 KV

emission current: 3 - 5 A

Thanks for your time and attention in advance, I hope you kindly find time and consider replying me,

Dr. Haghighi

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