sputtered film thickness?

Anthony Flannery flannery at leland.Stanford.EDU
Fri Aug 25 16:05:05 PDT 2000


Hi,
You are limited by stress, and ultimately by the size of the target.

Stress can be affected somewhat by changing the pressure.  The lowest
you can sputter at is somewhere around 3.5 mTorr.  As you go higher, you
incorporate more gas in the film.  At some point it becomes more like
swiss cheese and it will wipe off the wafer.  You can safetly sputter up
to around 6 mTorr.  Above that check the film.  General rule is that
lower pressure -> more compressive but that's not univeral at all.

Stress can also be affected by power settings.  Every metal is
different.  You'll have to do some tests to determine the settings for a
reasonable dep rate and a low stress film.  Too low and no dep rate, too
high and you can melt the target (and gun) so you want to stay
reasonable.

Temperature can work against you because of thermal expansion
mismatches.  I always intened to do a study and find out just how hot
wafers got during sputtering, but never did.  You may have to turn the
power off in the middle of a long sputter to let the wafer cool, and
then resume.

The ultimate depth depends how the target wears.  THis is different for
every metal.  Be VERY VERY VERY careful that you do not blast through
the target and start etching the gun.  You contaminate the machine with
thermal paste and the company that made the guns no longer exists. Then
people won't like you and won't invite you to parties.

Based on my work with other metals, the best guess for an ultimate
thickness of CU with one wafer, provided stress is not an issue and you
pulse the deposition is somewhere around 15 um.

Hope this helps.  Good luck.

Tony


john chiaverini wrote:
> 
> metallica users,
> 
> i was wondering what thicknesses it is possible to sputter to in
> metallica.  i'm hoping to do Cu, but i need a rather thick film.  any info
> would be appreciated.
> 
> thanks...
> 
>       _      _
>      (_)__  / /  ___   john chiaverini       jac17 at leland.stanford.edu
>     / / _ \/ _ \/ _ \
>  __/ /\___/_//_/_//_/  america is a vast conspiracy to make you happy.
> |___/                                                    --john updike



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