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

[Robert Vandusen]

Hi Aaron.
Back in 2015 we had similar concerns with our Balzers BA 510 thermal/ebeam evaporator.   We had reintroduced thermal capability to our system and had modified our internal SS shielding to allow us to have a direct line of sight to the thermal melt through a glass slide mounted on the shield and through one of the window viewports. Prior to this we only used ebeam evaporation and the shielding blocked the viewport.    As you have found, I was unable to find any literature on x-ray exposure concerns outside the chamber area.
I contacted our Health and Safety department who helped conduct x-ray testing during ebeam evaporations of a few different materials.   They found no measurable x-rays coming through the viewport or elsewhere on the chamber.  This satisfied our safety concerns.  However since the system was now identified as an potential x-ray producing source we had to get an Ontario ministry of labor x-ray permit and post it at the room doors and on the system.  It basically requires us to get a new assessment if we make any changes or modifications to the system that could result in increased exposure.
So we have piece of mind, but now a lot more questions when users see the x-ray signage.

Hope this helps.
Rob
   Robert Vandusen
   Microfabrication Cleanlab Facility Manager
   Electronics Department
   Carleton University
   room: 4184 Mackenzie Building
   613-520-2600 ext 5761
   Robert_vandusen at cunet.carleton.ca<mailto:Robert_vandusen at cunet.carleton.ca>



From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> On Behalf Of Aaron Hryciw
Sent: May 27, 2020 11:21 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Hazard due to x-ray production in e-beam evaporators?

[External Email]
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<http://www.nanofab.ualberta.ca/>
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