[labnetwork] Spot issue in Unaxis-750 PECVD

[Paolini, Steven]

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
www.cns.fas.harvard.edu

From: labnetwork <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
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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