[labnetwork] CdTe Safety

[Kathy Anderson]

Hi Mike,

Thanks for responding with ideas.

We are thinking of depositing ONTO CdTe, at first with ebeam evaporation (Al2O3 then Au), then sputter (ITO) on top of those.  We wonder how much Cd is freed during ebeam and will deposit onto evap chamber walls as well as migrate through grain boundaries to be available at substrate surface to later be scattered after transfer into the sputter chamber.

We do not have GaAs in the facility that I know of.  Gallium oxide we do have.

What temp check method would you do on the blank?  Would you introduce a new thermocouple to the respective chambers or some other method?

Thanks again,

Kathy

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________________________________
From: Yakimov, Michael <myakimov at albany.edu>
Sent: Monday, November 18, 2024 12:56 PM
To: Kathy Anderson <kathy.anderson at utah.edu>; labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: Re: CdTe Safety

Can you clarify a bit - are you depositing ON CdTe/CZT. or you're depositing THE CdTe/CZT? Two totally different situations


I did work with CdTe in the past , and now do some with CZT - not processing, though - and always thought that they should not be heated, but at room temperature are not an issue - well, not more than GaAs. Crumbs and shavings are bad, bulk crystal is inert.

If my memory serves me right, thermal budget for CdTe  is pretty low, to the point regular photoresist process may be an issue. Hence evaporation may also be too much thermal load as well, especially if high temperature stuff like Pt is involved (and it is a common contact for CZT) - but that should be primarily for the sample condition and researchers wouldn't want to push things that way. Check substrate temperature on a blank first... If that is all done, chamber and pump should be just fine. If you are concerned about pieces and dust... do you have any GaAs in the facility?


On a separate note, I generate ample amounts of arsenic waste - and was told it goes "to a secure landfill" or "forever storage facility", whatever that means. I suspect CdTe waste should be the same.



mike

_______________________________________________

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

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Kathy Anderson <kathy.anderson at utah.edu>
Sent: Wednesday, November 13, 2024 2:49 PM
To: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: [labnetwork] CdTe Safety


Hello Lab Network,



Will you share with us at the University of Utah your experience analyzing the occupational hazard of processing CdTe in your research lab?



We acknowledge the sublimation energy for CdTe is low, and the Cd escapes more readily leaving a Te rich surface.  At the same time, quantifying the health and operation risks associated with e-beam and sputter processing is proving a challenge as we communicate with our community of researchers what is and is not allowed in our toolset and why.



  *   Are you depositing films onto CdTe substrates using e-beam evaporation?  If not, why?
  *   Are you depositing films onto CdTe substrates using sputter?  If not, why?
  *   What is your lab’s procedure for maintaining a safe breathing space during e-beam and sputter chamber maintenance?
  *   How do you dispose of CdTe contaminated solids waste?
  *   How do you dispose of deposition equipment pumps that may be contaminated with CdTe as they fail?
  *   What is your lab’s CdTe substrate surface preparation process before e-beam or sputter?
  *   Do you have equipment dedicated to CdTe processing as well as separate equipment where CdTe substrates are prohibited?  If your deposition equipment is not separated between CdTe vs non CdTe, what limitations do you set on those processes to ensure cross-contamination of Cadmium or CdTe is negligible from run to run?





Regards,



Kathy Anderson

Cleanroom Process Engineer and Safety Officer

801-213-6555

801-440-1465



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