[labnetwork] Hazard due to x-ray production in e-beam evaporators?

[Aaron Hryciw]

Dear colleagues,

One of the users in our open-access facility recently expressed concern
about x-ray production in electron-beam evaporation systems.  Since the
typical acceleration voltage in our e-beam systems is 7–10 kV, he was
concerned that bremsstrahlung and characteristic x-rays would be generated
during deposition, with a maximum energy of 7–10 keV (soft to hard x-rays),
and that these x-rays would pose a health and safety hazard to an operator
standing next to the viewport for ~30 minutes.

A literature search yielded a few reports describing radiation damage to
sensitive devices from x-rays produced during an e-beam metallization step,
but I did not find any mention of related health and safety
considerations.  While some x-rays are undoubtedly produced, presumably
there are reasons why they are not hazardous to an operator (e.g., perhaps
total x-ray output is very small, majority of x-ray spectrum is low energy,
x-rays do not penetrate stainless steel chamber walls or viewport windows,
etc.).  I would like to answer this user with specific physical arguments
as to why the hazard is insignificant, however, so any advice you could
offer to this end 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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