[labnetwork] Use of forming gas in cryo-pumped sputtering system

[Aaron Hryciw]

Dear colleagues,

Our open-access facility has a cryo-pumped, manual sputtering system
plumbed with argon, oxygen, and nitrogen, which is often used for reactive
sputtering (mostly oxides).  One of our users has requested the addition of
forming gas (5% H₂ + balance Ar) to enable sputtering of *a*-Si:H / SiO₂
multilayers, as described in this paper
<https://www.osapublishing.org/ao/abstract.cfm?uri=ao-43-17-3548>.  A
concern was raised, however, about the possibility of explosions in the
cryo during regeneration, as the frozen mixture of argon, oxygen, ozone,
and hydrogen is released as the pump is warmed up.

Does anyone have experience with using forming gas in a cryo-pumped system,
and/or know of any measures that could be taken to ensure these sputtering
processes could be performed safely?  Doing this on a system equipped with
a turbo pump would be better, but we are leery of putting a turbo on a
manual system, where users fairly routinely crash the cryo.  As always, any
advice would be greatly appreciated.

Many thanks.

Cheers,

 – Aaron



Aaron Hryciw, PhD, PEng

Fabrication Group Manager

University of Alberta - nanoFAB

W1-060 ECERF Building

9107 - 116 Street

Edmonton, Alberta

Canada T6G 2V4 Ph: 780-940-7938
www.nanofab.ualberta.ca
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