[labnetwork] [EXTERNAL] Re: Contamination control in a UHV co-sputtering system (AJA Orion)

[Su Gupta]

Dear Filippo,

I have over forty years of experience in sputtering thin films of all kinds. Here are my answers to your questions.

1.  Cross-contamination between adjacent targets is not a problem at all since dark space shields are used. We have sputtered more than forty layers of up to seven different materials in the same chamber, with no cross-contamination, and sharp interfaces of atomic layer thicknesses.

2. If the photoresist is hard-baked you should be fine with sputtering on it at ambient temperatures.

3. We have used Kapton tape extensively in our UHV sputtering chamber at temperatures up to 500 degrees C with no problems at all.

Please don’t hesitate to contact me if you have any questions about sputtering.

Best regards,
Su

Subhadra Gupta, PhD
Fellow, American Vacuum Society
Professor Emerita
Metallurgical and Materials Engineering
Former Director
Micro-Fabrication Facility
University of Alabama
https://sites.ua.edu/sgupta


On Aug 11, 2026, at 1:47 PM, Gary Riggott <riggottg at mit.edu> wrote:


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Hi Filippo-

We have 2 Aja Orion systems here. One is for 4 inch wafers and wafer pieces, the other can accommodate 6" wafers and pieces.

We manage these tools differently.  The 4 inch tool has fewer restrictions, meaning that we allow resists for lift off processes and Kapton tape to secure samples.  In the other tool, we don't allow either of these.

1- I'm not sure what to say about cross-sputtering.  You can minimize this by using gun positions that are widely spaced, as opposed to being adjacent or near each other.  One thing to be aware of is the vapor pressure of the materials that you deposit.  For example, sulfur containing compounds tend to have high vapor pressures.  Once this is in your chamber, it may be hard to reach your original chamber base pressure.

For chamber and parts cleaning, we have a grit blaster that uses glass beads to remove deposits.

Lab users have much higher rates of success with lift off processes done in our evaporators, but many still use the sputter tools.

2- We allow a wide range of resists, like LOR 10A.  In the photo of our tool, you may notice an RGA.  We generally don't see any peaks beyond O2 at 32 amu.  Photos may not transmit thru Labnetwork.

3- We are OK with Kapton in one of our tools.  The adhesives are silicone based adhesives, and I can't find outgassing data on these adhesives no matter whom I ask or where I look.

Hope this helps,
Gary

Gary Riggott
508-451-0905

On 8/10/2026 10:13 PM, #MARTINELLI FILIPPO# wrote:
Dear labnetwork community,

I have recently been put in charge of a UHV magnetron sputtering system (AJA Orion) that I need to maintain and operate. The machine is dedicated to co-sputtering of two metals in a nitrogen environment.

The previous operator strongly advised me to be careful about what goes into the chamber, as contamination can affect both the chamber condition and the properties of the deposited material. However, she was not very specific about what exactly causes contamination, and I am unsure how restrictive I should be with the materials I load.

I have a few questions I would appreciate your opinion on:

1. I read that cross-sputtering can occur between nearby substrates, or between the substrate and the chamber. In your opinion, are there materials that are particularly prone to cross-sputtering and hard to remove with standard cleaning routines, and that should therefore be avoided in the chamber altogether?

2. Following on from that, what is your take on lithography resists?

3. How about mounting materials such as Kapton tape or Crystalbond?

I am quite new to this, so any suggestion or recommendation is welcome. I look forward to hearing your opinions.

Cheers,
Filippo



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