[labnetwork] Liquid Appearing in ICP Cl Chamber?!

[Ryan Rivers]

Hi Emma,

I think this might be LiF byproduct. If this is your LiNbO3 etcher, and I
recall you etch LiNbO3 with a CFx style gas? I may have my gases wrong.
That can generate LiF byproduct which can't vaporize, but can be sputtered
into crevices. LiF is notoriously hygroscopic, and highly soluble in water.
That would explain the sudden transition to liquid phase. Probably runs
LiF + H2O -> LiOH + HF as more H2O soaks into the droplet from the air, and
it's not going to let that H2O back out until it's saturated with water to
the point that the LiF stops splitting.

IMO, treat it like an HF droplet on a sink deck, don't get it on you, and
wipe with DI water until surface tests neutral. Alkali salts clean up in
water quite well for all of the above reasons.

-Ryan

On Thu, Oct 8, 2026 at 4:55 PM Emma Anquillare <eanquillare at gc.cuny.edu>
wrote:

> Dear Wise Lab Network Oracle,
>
> I already shared this with a few tool managers and so far no one else has
> ever run into it, but maybe someone on here has:
>
>
> Last week I went to vent and wet clean our ICP-Cl etcher. Our tool can
> only vent using Nitrogen, but I had recently become aware that it's
> considered a good practice to also then vent to atmosphere, so that if
> there are residues in the chamber that may react with atmospheric moisture
> to form HCl/HF vapors they can react fully and be pumped away before the
> chamber is opened. We don't have this capability, but to compensate I had
> started letting the tool sit in atmosphere for about an hour so (with a
> sign telling people to avoid the immediate area) so that even if any of
> these compounds had been present in unnoticeably small quantities, they
> could degas before I scrub it (wearing a full face respirator- we don't
> have a snorkel or air scrubber. That said, other technicians have
> previously been around this open chamber for days without a respirator and
> never mentioned any vapors or compounds.) The first time I added the hour
> wait, I did not notice anything unusual.
>
> The last two times I opened the chamber, I've noticed small quantities of
> white solid on the lower crease of the metal rim. It's there when I first
> open the chamber, but then significantly reduces or disappears all together
> by the time the hour is up, so clearly it is reacting with something in the
> atmosphere. We have had white residue in the chamber before that XPS
> indicated was likely a fluoropolymer, but this has a very different look to
> it, and a fluoropolymer would not be so reactive (see attached photos).
>
> Then, last time I went to clean the chamber, I came back after the hour in
> atmosphere to find not only had the white stuff reacted away, but liquid
> droplets had now formed on the metal ring beneath the liner a few inches
> away (See photos- though the entire metal ring appeared to also have a
> sheen to it- so I'm not sure if this was related or something new). The
> liquid was highly acidic (pH strip 0-1) , so we adjusted our clean to first
> wipe with a dry wipe, then water, and then only finished with IPA. The tool
> took longer than usual to pump down again (water on the O-ring?) but the
> next day it passed leak-up rate no problem.
>
> Has anyone ever encountered a liquid in the chamber upon atmospheric
> exposure? (or ever?) Any idea what any of this might be? (A recent clip of
> the log is attached- though the 'element soup' method quickly turns into a
> very large number of potential compounds ). More importantly, If this
> happened to you, how might you adjust your safety and PPE practices
> accordingly?
>
>
> Thanks!
>
> (PS- A few years ago I shared our SOP for chamber wet cleans and mentioned
> using acid gloves. I recently realized IPA actually breaks through trionics
> fairly quickly (~25min), so for PPE I have now been using nitrile gloves on
> top of acid gloves, which seems effective.)
> *_____________________________________________*
> *Emma Anquillare, PhD*
> Research Scientist
> ASRC Nanofabrication Facility
> City University of New York
>
> *Catalyzing Change, Celebrating Gains: *
> *A decade of visionary science for the public good.*
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