Interesting thread, so interesting I thought I would give my little nickel's worth.

According to the brief accompanying the referenced paper, shown below snipped from the website http://www.triquint.com/company/quality/pubs/symposiums/, MESFET GaAs devices are different from MOSFET or CMOS devices:

<snip>
Lack Of Latent and Cumulative ESD Effects On MESFET-Based GaAs ICs (request a copy)
Presented at the EOS/ESD Symposium, Anaheim, CA
Tony Rubalcava & Bill Roesch, September 1988, 3 pages.

The purpose of this study is to demonstrate that GaAs IC structures have no latent or cumulative effects from ESD pulsing. These findings are of significance because GaAs devices can offer an advantage over MOSFET-based silicon ICs which are susceptible to latent damage resulting in degradation or field failures. 
<eos>

However, for CMOS devices and most if not all FETs, ESD damage can be and typically is cumulative.  Many studies and papers have proven beyond doubt the damage, static and cumulative, caused by ESD.  I believe Motorola (long before divesting their logic and discrete product lines) (or somebody) did a study on the effects of ESD to show the necessity of integrated clamping diodes for inputs on the substrate.  There was included an SEM of the damage from an ESD pulse.  The pulse created an arc between the interconnect and gate oxide, and had blown out about half of the interconnect trace and some of the adjoining substrate.  Imagine what the next pulse would do.

http://www.ece.rutgers.edu/~kpckpc/Papers/MicroER3.doc  Interesting paper on gate-oxide degradation due to over-stress of component due to ESD and other causes.

http://staff.ub.tu-berlin.de/~harloff/resint/engmat/znovar.pdf Interesting paper and analysis of ZnO varistors and grain boundary degradation, along with method(s) to improve operation.

Whew! That was fun... back to the salt mines.

Everybody have a ***good*** Friday! (doin' the Snoopy(tm) dance)

Roger M. Stoops, CID+
Trimble Navigation Ltd., Dayton, OH, USA
Ph: +01 937.245.5288
Fax: +01 937.233.7511


-----Original Message-----
From: Matthias Mansfeld [mailto:[log in to unmask]]
Sent: Friday, October 03, 2003 5:49 AM
To: [log in to unmask]
Subject: Re: [TN] Cumulative damage from ESD


On 2 Oct 2003 at 16:44, Alex Krstic wrote:

>
>
> Hi all.  Simple question yet I haven't read the definitive answer.  Is
> damage from ESD cumulative?  Reason I ask is the following statement I
> came across in a GaAs MMIC article.
[...]
>
> I've always preached that ESD damage is cumulative.
>
> Alex "Shocked" Krstic
> NovAtel Inc.

I would say it depends. Usually I think we are on the safe side if we
assume it's cumulative unless the basic physics state there is no
degradation.

My favourtite example: Remember the big varistors in power supplies.
If the power line _has_ transients, the varistors _will_ degrade more
and more, until the leak current is high enough for incineration
(thus, industry began to make special varistors with incorporated
irreversible thermo fuse).

Other side, if you know your transients are short enough and energy
limited, you can live with suppressor diodes instead, please the _big
fat expensive_ ones, and they will not degrade unless your transients
exceed the maximum ratings. If they die, they don't die slowly by
unsoldering themselves or roasting your power supply slowly, they die
spectacularely and leaving usually with a rock solid short.

I would say the same conclusion can be made for any device. If the
construction can dissipate the energy of a discharge, I would assume
no cumulative damage (and there is the little difference between a
suppressor diode and a FET gate).

Regards
Matthias Mansfeld

--
Matthias Mansfeld Elektronik * Leiterplattenlayout, Bestueckung
Am Langhoelzl 11, 85540 Haar; Tel.: 089/4620 093-7, Fax: -8
Internet: http://www.mansfeld-elektronik.de
GPG http://www.mansfeld-elektronik.de/gnupgkey/mansfeld.asc

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