For a review of the concept of low-stress metal sputtering,
see the series of papers in the journal Thin Solid Films by Thorton and Hoffman.
To summarize, if metal atoms land on the growing film at low energy,
the film tends to be tensile. This is my experience for both evaporation
and for sputtering.
In sputtering, by raising the power and by lowering the pressure,
sputtered metal atoms have more energy as they strike the surface
of the growing film. This results in "atomic peening," changing
the stress toward compressive. (The resistivity also decreases.)
I have varied the pressure while keeping the power constant in a CPA sputterer
for aluminum, but the lowest stress I got was about 50 MPa.
I have evaporated gold, getting stress below 10 MPa for a slow deposition rate.
Unfortunately, for both aluminum and gold, the stress increased (more tensile)
over time. This is probably from room-temperature annealing
for these low-melting-point metals.
Thermal processing further increased the stress in the gold.
The evaporated chromium I have studied had a huge as-deposited stress,
around 1000 MPa.
--Kirt Williams Consultant
> -----Original Message-----
> From: Stefan Junge [mailto:[email protected]]
> Sent: Monday, March 10, 2003 12:14 AM
> To: [email protected]
> Subject: [mems-talk] Low stress sputtering of Gold / Chromium /
> Aluminium
>
>
> Hi,
>
> I want to sputter Gold, Chromium or Aluminium
> nearly stress free ( between 0 MPa and 20 MPa ).
>
> Can anybody tell me, if it's possible and where can
> I find more information about it?
>
> I have seached in www.sciencedirect.com, but could not
> find papers about it.
>
> Best regards,
>
> Stefan Junge
>
>
>
> --
> Institute for Microsensors, -actuators and -systems (IMSAS)
> University of Bremen
> Dipl.-Ing. Stefan Junge (Ph.D student)
> Dep. 1: Physics/Electrical Engineering
> Otto-Hahn-Allee
> 28359 Bremen, Germany
>
> P.O. Box 330 440
> 28334 Bremen, Germany
>
> Tel.: +49-421-218-3586
> Fax.: +49-421-218-4774
> E-Mail: [email protected]
> Internet: www.imsas.uni-bremen.de
> Privat HP: www.stefanjunge.de
>
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