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Q&As since 1989
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Sputtered aluminum is not shiny despite a clean sample and a leak check
Q. Hi,
I'm working at a research lab in Queens University as a research fellow. I'm trying to coat piezoceramic or even glass with a layer of aluminum thick enough to be wire bonded to. The aluminum is sputtered down on a titanium adhesive layer, and the Argon pressure is 5 mTorr, the vacuum may not be good but is as good as possible at 4x10^-6 torr. The aluminum comes out very cloudy even on clean glass and isn't brilliant for wire bonding either. I've leak checked with helium and not a problem, and I replaced some of the piping, cleaned out the vacuum vessel, and tried higher argon pressure up to 20 mTorr. Can anyone suggest what's going wrong here?
Thanks if you can suggest something.
Kind Regards,
Andrew Houlson- Kingston, Ontario, Canada
A. What bias voltage are you putting on the substrate? Without any ion bombardment during the deposition, the aluminum coating will have a very open structure. Adhesion won't be very good either.
Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover - San Diego,
California
A. Thick vacuum deposits (without concurrent ion bombardment) develop a columnar microstructure with a high surface area. For aluminum this gives the surface a white (light scattering) appearance which will look "mossy" from different angles of view. The deposited aluminum can be burnished if you want a shiny surface but the oxides may give you trouble with bonding. Ion bombardment during deposition can densify the film.
Donald M. MattoxSociety of Vacuum Coaters
Albuquerque, New Mexico
"Handbook of Physical Vapor Deposition (PVD) Processing" (2010) [on AbeBooks or eBay or Amazon affil links]
and "The Foundations of Vacuum Coating Technology" (2018) on AbeBooks or eBay or Amazon affil links]
Q. I am having the same problem. First off, one of the guns that I am using doesn't seem to want to ignite the plasma. I have tried everything to try and help it, but it just doesn't seem to work. So I tried using another gun that we have next to it, in the chamber and we end up sputtering a white cloudy Aluminum Layer. We are trying to sputter it on A low-k at 200 watts 6 mTorr at a pressure of ~10^-7 or so.
John MarshUniversity - Austin, Texas
2006
A. Check that the substrate is not getting too hot and it may be evolving water vapour during deposition and thus you are depositing Al2O3. Or you may have an air or water leak and a similar effect is occurring. Leak check your system and check you have clean (water vapour-free) Ar lines.
Robin Holmes- Hastings, Sussex, United Kingdom
August 3, 2010
Q. I have been having the same issue. I run my samples with a chamber pressure of 1.3(10^-3) at 90 watts for about 2 hours. I've been using liquid nitrogen to avoid moisture in the chamber but my samples have been consistently cloudy. I am currently running another sample in which I refill the liquid nitrogen to ensure the water vapor isn't oxidizing my samples.
Kassi Smith- Pullman, Washington, USA
February 25, 2011
Problem in aluminum sputter coating CD/DVD
Q. Dear sir,
We have a VDL-Odms Profilinear (Netherlands). We face a problem during aluminium sputtering. After target and Mask Change, the system requires Initialization process first and it's read its watt & energy first, and then it go in production. Our line was going well in production and one day a CD stuck inside of Chamber (internal handler).
We removed internal handler and removed the stuck disc and assembled again. And after that system is not initialized. Changed all its parts & argon valve also, and set the process parameter also but can't resolve it. Finally we interchange the metallizer (whole system ) with other machine and it's working smoothly.
Can you sugest what is the reason for it? I do all the things (e.g., B&R PLC, load lock pump, Vacuum Pump, mass flow controller (Argon), pirani gauge, vacuum gauge. Hard disk change -- all things done up to maintenance level. Finally I have only doubt on gear motor, so we change the metallizer with other machine and run the line. But in same case of problematic metalizer, when we put silver or copper Target it will immediate initialize and go into production; but in case of aluminium it doesn't. Please suggest.
Praveen PandeyEngineer- Optical division - GANDHIDHAM,Gujrat, India
April 22, 2014
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