[labnetwork] [External] Question about DC sputtering of zinc

[Rebecca Bolt Ettlinger]

Hi Sandra,

We have allowed Zn in a thermal evaporator here at DTU Nanolab (a multi-user university facility). We didn't allow it in our sputter systems as we were concerned about the cryo pumps on those systems being overloaded. Zn was not so easy to control in thermal evaporation and we concluded that the optimal solution would be sputtering in a dedicated system with a turbo pump.

After evaporation of course Zn was all over the chamber so it required thorough cleaning and also several "bakeout" evaporation runs of Al to get rid of Zn in the deposited layers (we usually use the evaporator for Al and Ag and the chamber gets heated most from the Al evaporation). We checked the deposited Al for traces of Zn by XPS before and after allowing Zn in the chamber and eventually got back to a state where the Zn was not detectable by XPS. We have had no user complaints afterwards but are wary of letting future users deposit Zn again because of the work involved to clean it out and check whether it is gone.

All the best,
Rebecca

Process specialist at DTU Nanolab, Technical University of Denmark

From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of Vlahakis, James
Sent: 1. februar 2023 16:43
To: Malhotra, Sandra Guy <sandra.malhotra at tamu.edu>; Fab Network <labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] [External] Question about DC sputtering of zinc

Hi Sandra, a few years ago we allowed Zn deposition in our "dirty" sputter tool without a heated platen. Consider the attached vapor pressure v Temp chart - at the temps seen in our tool the vapor pressure is below the system base pressure. Since that time we've noted no significant changes in base pressure and other users haven't complained about their films being lower quality.

Please take this with a grain of salt - Zn dep is not very common here, just a few times per year. In addition, our users are not fabricating CMOS devices, almost all are biomed focused these days

jim


From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Malhotra, Sandra Guy
Sent: Monday, January 30, 2023 4:40 PM
To: Fab Network <labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>>
Subject: [External] [labnetwork] Question about DC sputtering of zinc

Howdy All from AggieFab,
We have a user who requested permission to sputter zinc in our shared Lesker PVD75 DC sputtering tool.  On the Lesker website, there is the following note:

"This material has a relatively high vapor pressure at low temperatures which can cause ppm level contamination in the chamber and subsequent films. Careful consideration should be taken before this material is used in any deposition system. For this reason, some users prefer to use only dedicated vacuum chambers for deposition."

I'd like to ask the group if they allow zinc depositions in their shared tools if they follow it by a thorough paste with another material, like Ti? Or if this material is prohibited because it is problematic.

Thanks in advance for any inputs you may have.

Best,

Sandra G. Malhotra, Ph.D.  |  Technical Lab Manager

AggieFab Nanofabrication Facility
https://aggiefab.tamu.edu/
Department of Electrical & Computer Engineering, College of Engineering | Texas A&M University
3253 TAMU | College Station, TX 77843
ph: 979.845.3199  |  sandra.malhotra at tamu.edu<mailto:sandra.malhotra at tamu.edu>
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