[labnetwork] Lead (Pb) evaporation

[Owain Clark]

We had thermocouples with plates attached for monitoring of indirect substrate IR heating in our old 1.15m throw lift off evaporator. Which was also very useful for monitoring lift off processes, as a general indicator of wafer temperature. Any deposition with reasonable power such as Pt indeed could easily heat to ~120C without too much trouble. Even low power Al could, as the crucibles had a large emitting IR area with a full melt.

I think the record was Ta or Mo, we easily went over 150C and had to run the deposition in several shorter runs to not cook the negative resist.

BR, O.

From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of Yakimov, Michael
Sent: Wednesday, July 17, 2024 2:04 PM
To: Youry Borisenkov <yb2471 at columbia.edu>; Fab Network <labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] Lead (Pb) evaporation

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EHS concerns aside, I wouldn't go with the idea for cross-contamination and process control reasons.
My personal rule of thumb is 1e-6 at 600C to start the conversation.Pb has a vapor pressure of 1e-6 at 420C.
 For <600C materials that means they will evaporate before crucible is red hot - hard to tune electron beam and visually control the deposition that way. May be easier with resistive process though.
The other thing is when you're running something high temperature, like Pt or Mo, things become pretty hot inside. Anecdotally, I had substrate - pretty far away from the source - go above 150C during Pt deposition. I don't know how high the source shutter would go, but 400C seems pretty plausible. Re-evaporation isn't something people like to think about in terms other than how to avoid that...




_______________________________________________

Michael Yakimov

Research scientist

Department  of Nanoscale Science and Engineering

University at Albany - State University of NY



253 Fuller rd.

Albany NY 12203



Phone: 518-437-8609 lab

e-mail: myakimov at albany.edu<mailto:myakimov at albany.edu>

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> on behalf of Youry Borisenkov <yb2471 at columbia.edu<mailto:yb2471 at columbia.edu>>
Sent: Tuesday, July 16, 2024 3:57 PM
To: Fab Network <labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>>
Subject: [labnetwork] Lead (Pb) evaporation

Hi All,
Do any of you allow Lead (Pb) deposition on your evaporation tools?
If so, what are the precautions that you take to avoid Lead exposure hazards during PM,etc?

--
Thank you,
Youry Borisenkov
CNI<https://cni.columbia.edu/columbia-university-clean-room>
Columbia University
CEPSR 1017, New York, NY, 10027, United States.
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