[labnetwork] Mystery White Solid in ICP-CL

[Sun, Yong]

Hi Emma,

This looks like some kind of fluoropolymer residue (may contain C, F, H, O) deposited on the cold ring-area near your ICP ceramic chamber. If you look closely, the main etching chamber sidewall doesn't have the same residue, suggesting that your main chamber wall is heated??? Maybe there are more etching processes that use only RF power (no ICP) recently, leading to the fluoropolymer residue accumulated on the cold ring-area near the ICP chamber.

If you want to create a more aggressive cleaning recipe after each user process, try SF6/O2 instead of CF4/O2, SF6 seems to leave less residue behind. The chamber cleaning should be slightly longer than the typical user etching process to reduce the accumulation of residue. The following is what I do for chamber cleaning in my ICP-RIE that runs both F- and Cl- recipes (15min or 30min cleaning):

(i) O2/Ar gentle cleaning: 30mtorr, 50sccm O2, 10sccm Ar, 50W RF, 500W ICP -- 2min~5min
(ii) O2/SF6 deep cleaning: 30mtorr, 50sccm O2, 10sccm SF6, 100W RF, 1500W ICP — 5min~10min
(iii) O2/Ar deep cleaning: 30mtorr, 50sccm  O2, 10sccm Ar, 100W RF, 1500W ICP -- 5min~10min
(iv) O2/Ar gentle cleaning: 30mtorr, 50sccm O2, 10sccm Ar, 50W RF, 500W ICP-- 3min~5min

I'd physically clean the chamber whenever users report dusts/white powder/defects on their sample. Such residue typically means that, not sufficient chamber cleaning has been carried out by certain users in the past.

Best,
Yong Sun

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Emma Anquillare <eanquillare at gc.cuny.edu>
Sent: Tuesday, June 9, 2026 5:59 PM
To: Network Fab <labnetwork at mtl.mit.edu>
Subject: [labnetwork] Mystery White Solid in ICP-CL

Dear LabNetwork Hive Mind,

I went to manually scrub out our ICP-Cl Etcher with IPA as I usually do every 1-2 weeks, and opened up the chamber to find large quantities of white powder caked along the upper portion of the metal rim near where it meets the ceramic liner.  Large amounts of it seemed to have fallen onto the table as well. (See Photos). Has anyone ever encountered this? Any idea what it might be?

Here are my suspicions and more details:

  1.
One of my colleagues commented that it looked like the Aluminum/a she gets in her deposition tools, and I was wondering if something is leeching out of the liner and it needs to be replaced? Might explain why it's concentrated at the border, and appears in such visibly large quantities for a nano-scale etch tool
  2.
The immediate suspect of course is also a solid etch product,  but we have not had any new or unusual materials in the chamber since the last cleaning two weeks ago (or at least, as far as users have told us). We have recently changed our clean recipes so that instead of just a blanket O2 clean for everything, there are now customized cleans based on what people are etching, but people seem to be following the rules on this pretty well (see attached). I have also attached a summary of what has been etched in the chamber since the last manual clean and using what gasses.  (We are aware LiNbO3 is not volatile, thus the regular manual cleanings). One thing that also occurred to me was the possibility of LiF formation with increasing amounts of CF4 being run from the new cleans and reacting with sputtered LiNbO3 in the chamber (but again, this seems like an uncannily large quantity of solid for that).

I collected some with kapton tape for XPS analysis, but curious to see if anyone else has encountered this, especially if it's an issue with the tool liner itself.

Thanks!
Emma



_____________________________________________
Emma Anquillare, PhD
Research Scientist
ASRC Nanofabrication Facility
City University of New York

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