[109476] in Cypherpunks
Re: About Alpha radiation...
daemon@ATHENA.MIT.EDU (Tim May)
Thu Mar 25 12:12:39 1999
In-Reply-To: <36F9EBD7.AFF2A1FF@wis.weizmann.ac.il>
Date: Thu, 25 Mar 1999 08:54:18 -0800
To: cypherpunks@algebra.com
From: Tim May <tcmay@got.net>
Reply-To: Tim May <tcmay@got.net>
At 11:55 PM -0800 3/24/99, Tim Griffiths wrote:
>Tim May wrote:
>
>> Alpha particles are a known problem with silicon chips. And I ought
>> to know.
>
>So should I, but I don't..:) Do you have any more details, i.e. Alpha's
>from what source/of what energy, under what conditions?
>
There are hundreds of references on this effect. Cf. George Messenger's
textbook on radiation effects in electronics, or technical papers presented
at the Nuclear and Space Radiation Effects Conference (and reprinted in the
December issue each year of "IEEE Transactions on Nuclear Science."
The alphas come from uranium and thorium and/or their daughters present in
varying quantities in ceramics, glasses, aluminum, and even plastics (with
fillers).
Energies typically range up to 6-9 MeV, with a distribution down to 0 (due
to self-absorbtion in the source).
Energy is shed in silicon so that an electron-hole pair is created for each
3.5 eV of alpha particle energy. Thus, a 5 MeV alpha produces about 1.4
million electron-hole pair. And this is within a track length of about 20
microns.
The effects on chips are interesting.
Again, much more is available on this.
Those wanting to go back to the beginning can read some of the papers I
wrote in 1978-81, including "Alpha-Particle-Induced Soft Errors in Dynamic
Memories," co-authored with Murray Woods, and published in the January 1979
issues of "IEEE Transactions on Electron Devices."
--Tim May
Y2K: Hope for the best, prepare for the worst, enjoy the ride.
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Timothy C. May | Crypto Anarchy: encryption, digital money,
ComSec 3DES: 831-728-0152 | anonymous networks, digital pseudonyms, zero
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