[labnetwork] Spot issue in Unaxis-750 PECVD

Mon Aug 23 09:40:43 EDT 2021

Hi David,
Nothing is changed recently.
We are using ULSI grade CF4.
For leak check, I have evacuated the silane gas line and found no leak. Is there any other method you would like to suggest?
Sure, I will discuss with my superiors and contact Plasma-Therm.

Thanks,
-Vibhor-

________________________________
From: Lishan, David (Plasma-Therm LLC) <david.lishan at plasmatherm.com>
Sent: Monday, August 23, 2021 8:29 AM
To: April, Mark R. <mapril at draper.com>; Paolini, Steven <spaolini at cns.fas.harvard.edu>; Vibhor Kumar <vk409 at soe.rutgers.edu>; labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: RE: Spot issue in Unaxis-750 PECVD

Hi Vibhor,

The imprint of the showerhead hole pattern is often an indication that silane is reacting with residual oxygen somewhere behind the showerhead.  The source of the oxygen could be a leak anywhere from behind the showerhead all the back to the main valves of the gas bottles.  If the CF4 clean gas is a premix of CF4/O2, it is possible that the oxygen is coming from there.  If there is small leak and the system has been left idle overnight, it is generally the first run of the day that shows the most pronounced imprint pattern.  Subsequent runs can show a less pronounced pattern.  Perhaps this is what has been described in the original problem statement.

Has anything been recently changed on the system e.g. silane gas bottle, mass flow controller or gas line?

Suggest contacting Plasma Therm Tech Support if the problem persists.

BR,

David

David Lishan, Ph.D., Sr. Member IEEE

Principal Scientist, Director – Technical Marketing

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From: labnetwork [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of April, Mark R.
Sent: Monday, August 23, 2021 6:48 AM
To: Paolini, Steven <spaolini at cns.fas.harvard.edu>; Vibhor Kumar <vk409 at soe.rutgers.edu>; labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Spot issue in Unaxis-750 PECVD

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Good Morning Vibhor,

I concur with Mr. Paolini.  I had a similar issue on a PECVD tool.  After a thorough shower head clean, including the diffuser plate, the shower head pattern was eliminated.  This routinely gets done each year now, during a major PM.  You may need to perform more due to your usage.

Hope this helps.

Mark R. April
Senior  Equipment Engineer

Microfabrication Laboratory
[color_logo_small4]
555 Technology Square

Cambridge, MA  02139

mapril at draper.com<mailto:mapril at draper.com>

O # 617-258-1613 C # 617-455-1596

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From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Paolini, Steven
Sent: Friday, August 20, 2021 4:02 PM
To: Vibhor Kumar <vk409 at soe.rutgers.edu<mailto:vk409 at soe.rutgers.edu>>; labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] Spot issue in Unaxis-750 PECVD

Vibhor,

  You are most likely seeing the effect of the showerhead being in need of cleaning, particularly the backside. The Deposition of dielectric films creates a powdery substance just outside of the intended plasma concentrate. This debris, over time, will allow small reactions to happen under the showerhead and show up as spots on your wafer, most likely in the pattern of the holes in the showerhead. I would suggest removing the showerhead and diffuser plate and performing a very thorough clean on all the parts. In my experience, and depending on the usage, this should be performed routinely at an interval that keeps the effect at bay.

  Hope this helps,

    Steve Paolini

   Equipment Dood

Steve Paolini

Principal Equipment Engineer

Harvard University Center for Nanoscale Systems

11 Oxford St.

Cambridge, MA 02138

617- 496- 9816

spaolini at cns.fas.harvard.edu<mailto:spaolini at cns.fas.harvard.edu>

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From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> On Behalf Of Vibhor Kumar
Sent: Friday, August 20, 2021 1:49 PM
To: labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>
Subject: [labnetwork] Spot issue in Unaxis-750 PECVD

Hello Everyone,

During nitride/oxide deposition with Unaxis-750 PECVD, we are getting a mirror image of shower head on the wafer, i.e., spots. We cleaned the chamber with CF4 for 2 consecutive days, each day 4:30 hrs. The conditions were

CF4 = 100 sccm, Temp = 250 C, chamber pressure = 600 mT, time = 4:30 hrs

We also evacuated the silane gas line, but there is no leakage.

After completing the cleaning, when we conditioned the chamber and deposited nitride, the spots were lightened. But on the second day, the spots look enlarging again.

Can anyone please suggest solution to this issue?

Thanks,

-Vibhor Kumar-

Postdoctoral Associate

Rutgers, The State University of New Jersey.

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