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

[Aaron Hryciw]

Dear colleagues,

Many thanks for your recommendations to ensure safe regeneration of a
cryopump containing oxygen and hydrogen.  We'll run some numbers to ensure
we remain outside the flammability window for the hydrogen/oxygen mixture
released during regen, and take other prudent precautions (no fast regen
with heaters, venting purge gas to exhaust, etc.).

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



On Fri, Mar 15, 2019 at 10:12 AM Aaron Hryciw <ahryciw at ualberta.ca> wrote:

> 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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