[labnetwork] Decommissioning Silane and Phosphene Stainless Gas Delivery Lines

[Paolini, Steven]

Excellent question.
I cannot quote industry standards nor am I aware any exist, but the bottom line is many pump and purge cycles are in order. I would use the system for the pumping part of the procedure since it will pump well below what the venturi can provide at the cabinet. I would say that the exact # of cycles is up to you and your available time. If I were challenged with this, I would pump the lines down to the lowest level of vacuum achievable through your system and still allow it to remain there for at least a half hour (or more if your delivery lines are longer than 50 feet) since there are always some stubborn molecules of gas that have to crash into bends and ultimately enter the chamber. I would then run pure N2 through the MFC's at full scale for another half hour before repeating the cycle. I would do this at a minimum of 20 cycles.
In regards to disposal, I would treat the Phosphine lines as hazardous waste but the Silane lines should be relatively non-toxic aside from possible deposits of SiO2 (dusting). I hope that other subscribers can correct me if I am wrong about this but my methods have been  successful over the years.
Best of luck and be careful,
Steve Paolini
Equipment dood
Harvard Center for Nanoscale Systems.

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Hmelo, Anthony B
Sent: Friday, September 09, 2016 9:42 AM
To: labnetwork at mtl.mit.edu
Cc: Hmelo, Anthony B
Subject: [labnetwork] Decommissioning Silane and Phosphene Stainless Gas Delivery Lines

All:

VINSE is in the process of relocating a PECVD reactor to a new cleanroom facility and I am seeking advice on the industry standards for decommissiong Silane and Phosphene stainless gas delivery lines that run from the respective gas cabinets to the tool in its current location. Beyond thoroughly purging the lines with nitrogen flow through the tool and exhausting the purge gas  through the tool exhaust, are there other considerations involved in abandoning the gas delivery lines? For example, are the lines considered to be permanently contaminated and will they require special disposal?

Any advice on decommissioning these lines will be deeply appreciated.

With thanks,

Anthony B Hmelo, PhD

Associate Director, VINSE
Research Associate Professor of Physics and Astronomy
Research Associate Professor of Materials Science and Engineering
Vanderbilt University
Nashville TN 37235

615-343-7212

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