[labnetwork] Flooded ICP-RIE

Tue Aug 23 08:27:49 EDT 2016

Hello Peter,

Your mail brought back bad old memories. I once worked in a company where an ICP RIE chamber was flooded with silicone coolant oil, which leaked out from the cooled chuck and into the chamber. We were lucky that the oil leak was limited (less than half a liter). Luckily, the tool was under warranty, and the manufacturer cleaned the contamination with a combination of IPA, chamber heating and oxygen plasma. The chamber was at least partly disassembled for cleaning. I vividly remember standing with a rather big maglev turbo pump pouring IPA through it. In the end the manufacturer used a residual gas analyzer to prove that all contaminant had been removed.

Best regards,
Leif

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Peter Köllensperger
Sent: 22. august 2016 10:15
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Flooded ICP-RIE

Dear Labnetwork Members,

I’ve just recently started as process group leader here at NTNU NanoLab in Trondheim, Norway, but have been following the discussions on the mailing list with interest.

I now have a question of my own and would very much appreciate any thoughts or advice you may be able to share.

We are currently having preventive maintenance of our ICP-RIE systems carried out by the manufacturer.
Unfortunately one of their engineers mixed up the helium backing line with the coolant line from the chiller unit. When the chiller was switched on, it pumped ca. 1-2 litres of a water and Hexid heat transfer fluid into the main chamber and loadlock. The system was not under vacuum at the time. The RIE section was completely filled with water and the main chamber also had water in it.  The lifting pins assembly including bellows, the CM gauge the pirani gauge as well as the He line were completely submerged.
The engineers realised what was going on after the chiller gave a low level alarm and they saw the coolant level continue to drop. They stopped the chiller, opened the chamber, and mopped up the liquid with PIG pads and cleanroom cloths where accessible. They then switched on both the roughing and loadlock pump.
When the loadlock pump was switched on it died immediately. They realised that water vapour shouldn’t enter the scrubber and removed the exhaust line from the scrubber, but it is likely that some water vapour ++ entered the scrubber as steam was coming out of the exhaust. This means the entire system has been exposed to water/coolant mix, possibly with exception of the turbo pump, although there may have been some backstreaming from the main roughing pump.

Pumping the chamber from Thursday<x-apple-data-detectors://1> to the following Tuesday improved the vacuum from 1x10e-2 Torr with a leakup rate of 20 mTorr/min to 5x10e-5 Torr with a leakup rate of 5 mTorr/min. Specification is less than 1 mTorr/min.

Needless to say this causes a number of issues, some of which we may not even have thought to consider.

In our view, the issues can be divided into immediate Health and Safety concerns, and more long term concerns regarding the performance of an ICP RIE unit that has been flooded

1.       Regarding H&S issues we’re concerned about are the mixing of SF6, CHF3, Cl2 and BCl3 with water in the scrubber.

We will send the scrubber for a refill and check. We have contacted the vendor of the scrubber, his main concern is clogging of the granulate. Is there anything else we should pay attention to?

2.       Can a chamber be sufficiently reconditioned by in situ by cleaning, baking and running plasmas or will the coolant inside necessitate a more complete disassembly and clean?
Has anyone had a similar problem and how did you proceed? How would you suggest we ask the manufacturer to verify that there are no long-term detrimental effects on the instrument, the pumps or the processes run on the instrument?

I'd appreciate any thoughts you may have surrounding this issue.

Kind regards,

Peter

––––––––––––––––––––––––––––––––––––––––––––––

Dr. Peter A. Köllensperger
NTNU NanoLab
Sem Sælandsvei 14
Norwegian University of Science and Technology (NTNU)
7491 Trondheim

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20160823/aabad130/attachment.html>