[labnetwork] ALD cross contamination issue

[J Provine]

hi warren,
i would think this is a cross-contamination issue for MOS users because of
the Bi2Se3.  the Nb and sapphire, are not a concern.  if you really want to
do this, i think you need to eliminate physical contact (tweezers, sliding
on the heater of the chamber, etc.  luckily ald is relatively low in
temperature and you can paste the chamber after the run.  i'm assuming this
is a savannah ald tool.  some recommendations:
1) have them keep their pieces on a clean Si or oxidized Si carrier wafer.
2) the tweezers that go into chamber and touch the Si carrier wafer should
not be the tweezers touching the contaminated sample
3) after deposition run 200 cycles of alumina on an empty chamber to coat
everything down with 20nm of film (user should book this time as well).
4) (optional) to really be careful, you could make a MOSCAP before and
after the above three steps and compare performance.  if the chamber was
contaminated (as shown by CV degradation) you could put the user on the
hook cleaning the chamber - which would cause a few days to a week of
downtime.  but if everything is great, then the above can be the procedure
going forward.

we follow steps 1-3 for a GaAs and InGaAs samples because we found through
4 that it isn't leave a lasting issue.

hope this helps.
j

On Fri, Jul 27, 2012 at 12:58 PM, Warren Lai <warren.lai at rutgers.edu> wrote:

> Colleagues****
>
> ** **
>
> I have a cross contamination question on our Cambridge ALD tool.  A user
> requests to do Al2O3 on Bi2Se3 and Nb structures on sapphire (and prefers
> to use only acetone and IPA pre-clean).  Does anyone know:****
>
> **1.       **If there is cross-contamination issue for MOS users?****
>
> **2.       **Any procedure to minimize the contamination (Additional
> pre-clean or post-clean? Certain deposition to “bury” the contamination
> etc.)?****
>
> Several things to note are:****
>
> **a.       **The exposed areas are sapphire, Bi2Se3 and Nb****
>
> **b.      **The device is made by MBE and ion-milling, so the device (and
> exposed area of Bi2Se3 and Nb) is quite small****
>
> **c.       **Because of MBE, the Bi2Se3 is quality grade and “clean”****
>
> **d.      **They prefer pre-clean with only acetone and IPA (based on
> some limited experience of acid damage to the device)****
>
> ** **
>
> Your advice will be most appreciated.****
>
> ** **
>
> Best regards,****
>
> ** **
>
> Warren Lai, Ph.D.****
>
> Associate Director****
>
> Micro Electronics Research Laboratory (MERL)****
>
> Electrical and Computer Engineering Department****
>
> Rutgers, The State University of New Jersey****
>
> Room EE-115****
>
> 94 Brett Road, Piscataway, NJ 08854****
>
> 732-445-0680****
>
> warren.lai at rutgers.edu****
>
> www.merl.rutgers.edu****
>
> www.ece.rutgers.edu****
>
> ** **
>
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