[labnetwork] Sputter problem

[Gupta, Su]

Hi Steven:

Are you sputtering reactively or from a TiO2 target? Please give me power, pressure, flow conditions for your coating and cleaning cycles. That will help me to understand your problem better.

Thanks, Su

________________________________
From: Steven Foland [stevenfoland at gmail.com]
Sent: Friday, June 24, 2011 10:05 AM
To: Gupta, Su
Cc: Keith Bradshaw; labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Sputter problem

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<mailto: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<mailto:labnetwork-bounces at mtl.mit.edu> [labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>] On Behalf Of Keith Bradshaw [bradshaw1234 at gmail.com<mailto:bradshaw1234 at gmail.com>]
Sent: Thursday, June 23, 2011 5:09 PM
To: labnetwork at mtl.mit.edu<mailto: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