[labnetwork] Sputter problem

[Steven Foland]

Hi Prof. Gupta,

We are doing RF sputtering, not DC. Cleaning the target longer does increase
deposition rate temporarily, but it drops back down quickly. We are most
likely operating at the "oxidized" rate, but still are unsure why we are
experiencing this gradual decline in film thickness.

Here is my data from yesterday:
1st run: 5 minute clean cycle, 5 minute coat cycle: 250 Angstroms
2nd run: 5 min clean, 10 min coat: 198 Angstroms
3rd run: 10 min clean, 5 min coat: 118 Angstroms
4th run: 5 min clean, 5 min coat: 96 Angstroms
5th run: 5 min clean, 5 min coat: 80 Angstroms
6th run: 5 min clean, 5 min coat: 90 Angstroms
7th run: 20 min clean, 5 min coat: 120 Angstroms

So you see, we have a gradual decline in dep rate, but can increase the dep
rate slightly by running a longer clean cycle.

If enough time has passed (a day or two) between runs, the rate increases
back to its original value of ~250 Angstroms in 5 minutes.

Thoughts?

Thank you,
Steven Foland

On Thu, Jun 23, 2011 at 11:54 PM, Gupta, Su <sgupta at eng.ua.edu> wrote:

> Hi Keith:
>
> Can you give me some more details about your sputter system and the
> processs? For instance, are you sputtering reactively from a Ti target or is
> it TiO2? If you are doing DC reactive sputtering from an elemental target,
> then the target voltage is the best indicator of what is going on with the
> process. For instance, the target may be oxidizing further with each run
> (even with the preclean) and you may be dropping down the slope of the
> hysteresis loop from the 'metallic' rate to the "oxidized" rate, which would
> be accurately reflected in a drop in the target voltage. A small leak or
> outgassing could also cause this type of problem, but it probably would not
> be as regular and systematic as what you are observing.
>
> Regards,
> Su Gupta
> Assoc. Prof, MTE
> Faculty Director, uamcro
> Univ. of Alabama
> ________________________________
> From: labnetwork-bounces at mtl.mit.edu [labnetwork-bounces at mtl.mit.edu] On
> Behalf Of Keith Bradshaw [bradshaw1234 at gmail.com]
> Sent: Thursday, June 23, 2011 5:09 PM
> To: labnetwork at mtl.mit.edu; Steven Foland
> Subject: [labnetwork] Sputter problem
>
> We are sputtering TiO2 .
>
> We begin the day with a 250 angstrom rate....each subsequent run is reduced
> by 10-15% in rate until we are at a 125 angstrom rate.  We are not changing
> anything.
>
> Next day we begin again at 250.
>
> Tried argon clean between runs, tried 3 hour wait between runs, we are
> using a load lock and vacuum looks stable , still rate drops on each run.
>
> Any ideas?
>
> cordially,
>
> Keith Bradshaw
> Dallas
>
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