While we have been utilizing standard fluence levels such as those listed in the JESD57 document, we have begun revisiting what an appropriate test fluence is when it comes to qualifying a device for single events. Instead of a fixed fluence level or until a specific number of events occurs, a different thought process is required

LaBel, Kenneth A.

Ladbury, Raymond

NASA Technical Reports Server

To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Proton Particle Test Fluence:
What’s the Right Number?
Kenneth A. LaBel
ken.label@nasa.gov
Co-Manager, NASA Electronic Parts and Packaging 
(NEPP) Program
Raymond Ladbury
raymond.l.ladbury@nasa.gov
NASA Engineering Safety Center (NESC) Radiation 
Effects Lead
This work is supported by the NEPP Program
1
https://ntrs.nasa.gov/search.jsp?R=20150020829 2019-08-31T05:41:24+00:00Z
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Acronyms
2
Acronym Definition
Au Gold
DRAMs Dynamic Random Access Memory
DUT Device Under Test
EDAC Error Detection and Correction 
F Fluence
Gbit Gigabit
HST Hubble Space Telescope
IEEE Institute of Electrical and Electronics Engineers
ISC Irvine Sensor
LET linear energy transfer (MeV•cm2/mg)
MeV Million electronvolts
MHz Megahertz
NEPP NASA Electronic Parts and Packaging
nsec Nanosecond
Acronym Definition
Nucl Nuclear
Pb Lead
POF Physics of Failure
Pt Platinum
RHA Radiation Hardness Assurance
Sci Science
SEE Single Event Effect
SEFI Single Event Functional Interrupt
SEL Single-Event Latchup
SEU Single Event Upset
SOC Systems on a Chip
SSR Solid State Recorder
Trans Transactions
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Outline
• What’s fluence?
– Brief history lesson
• The factors that influence fluence levels:
– Number of transistors/nodes, 
– Number of dynamic operating states,
– Number of samples being used in flight, and
– Mission environment and particle kinematics.
• Considerations and implications
• Summary
3
http://journalofcosmology.com/images/StraumeFigure3a.jpg
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Definition of Fluence
• Fluence is:
– The number of particles impinging on the surface of a 
device during a single ion beam test run normalized to a 
square centimeter. Denoted F.
• It is NOT:
– Cumulative fluence: the sum of all individual fluence 
levels for all beam runs (usually only for a given test 
condition such as proton energy).
– Effective fluence: beam run fluence normalized by 
cos(θ), where θ is the angle of incidence.
4
Beam impinging on top or backside of device
Beam impinging on tilted device (angle of incidence)
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Motivation
• Each transistor and operating-state (in a dynamic system) 
has the same random probability of getting hit.
– That's the challenge: single event effects (SEE) are random* 
processes.
– In other words, the error signature will be a function of 
where a particle hits and when a particle hits in a dynamic 
operating system.
• Testing is an attempt to quantify this random process and 
provide:
– Reasonable coverage of the possible error signatures by 
getting sufficient particle fluences to provide confidence in 
coverage of the transistor/state space.
• For a billion-transistor, complex, system on a chip (SOC) 
device, how do we ensure this?
– This is the crux of this presentation: doing enough testing to 
have a reasonable level of confidence.
5
*Okay, it’s really a Markov process –
where the occurrence of an SEU in the future and past are independent.
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015. 6
Tradition: When Do We Stop a Test at the 
Particle Beam?
• Existing test standards provide guidance on setting a 
“beam stop” at either a given fluence or specific number of 
events.
• Fluence is (number of particles)/cm2 for a given test run
• JESD57* (the long time guidance for heavy ion SEE) gives 
recommendations of:
– A fluence of 1×107 particles/cm2, or
– 100 events, or
– Significant event (such as SEFI or SEL).
• Proton testing is often stopped at a fluence of 1×1010
protons/cm2 (or 100 errors or a significant event).
• Are these numbers taking into account:
– Physics of failure (POF),
– Circuit operation, and
– Sufficient statistics?
* JEDEC JESD57: Test Procedures for the Measurement of Single-Event Effects in Semiconductor 
Devices from Heavy Ion Irradiation, Revised 1996 – this is currently being revised
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
The Challenges
• There are four basic considerations for determining 
fluence levels:
– Geometry:
• The number of potentially sensitive nodes or transistors in the 
device (statistical node coverage).
– Operation (and propagation):
• The dynamic operation of the device under test (statistical 
state and error propagation coverage).
– Sample size:
• The number of samples of the device being used for test 
(statistical system and variability coverage).
– POF and (more) statistics:
• The environment exposure and particle kinematics (i.e., what 
happens when a particle strikes the semiconductor).
• For dynamic operations, we are looking not only at measuring a 
cross-section for rate determination, but capturing as many possible 
error signatures as reasonable to provide to design teams.
– A simple example is the range of transients induced in an amplifier.
7
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Geometric Node Coverage
• This is the simplest of the challenges to discuss. So 
consider,
– A memory device under test (DUT) has a Million memory cells 
(Mbit), -
• How many protons on the die surface are required to cover a 
sufficient number of potentially sensitive bits in order to obtain 
good statistics on variability?
• I.e., what’s the right number of “events” to detect versus array 
size?
– 1%?, 10%?, 50%?, 100%?
– What is the objective?
• Mean distribution? Corner cases? Other?
– 1% equates to 1000 events in this example, but what does that 
say about variability across the die?
• Consider 10% at a minimum
8
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Dynamic Operation Constraints
• Assume that a particle strikes a specific location (sensitive node). 
What can happen?
– An error can occur immediately,
– An error can occur at a undetermined time (and/or location) later (temporal 
or circuit propagation), or
– Nothing.
• Why? Let’s look at a Gbit memory.
– Assume it takes a minute to cycle through the address space.
• Errors may occur before I reach an address (I see the error), while I’m at an 
address (may or may not see the error), or after I’m at an address (don’t see it 
now, but may or may not see it later).
• Now look at a logic circuit such as a 32-bit counter.
– There are 232 states.
– Operational frequency of 50 MHz (20 nsec per state) – over 300 billion 
seconds to cover all states. Beam runs are too short to cover this statistically.
• Key is understanding the error signature space and propagation effect.
– Tests should be prognostic on capturing error signatures that designers may need to 
properly design fault tolerance.
– Remember, each state has the same random chance of taking a hit.
• Consider a truly complex device like a system on a chip.
• Operating state coverage (statistics), and error signatures.
9
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
(Sample) Size Matters
• Besides the usual discussion of statistical relevance of 
samples from a single wafer lot, consider what the test 
results will be applied to.
– How many samples in the flight application are being used?
• There’s a big difference between flying two samples of a device 
and one thousand!
• Outlier results are important when device is being used 
extensively. [1]
• It’s also important to grasp the idea of limiting cross-
section (i.e., no events observed).
10
How important is knowing outliers in SEE testing?
[1]  K.A. LaBel, A.H. Johnston, J.L. Barth, R.A. Reed, C.E. Barnes, "Emerging Radiation Hardness Assurance (RHA) Issues: 
A NASA Approach for Space Flight Programs," IEEE Trans. Nucl. Sci., Vol. 45, No.6, pp. 2727-2736, Dec. 1998.
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Example: Hubble Space Telescope (HST)
Solid State Recorder (SSR) – 1 of 2
• Contained
– IBM Luna ES Rev. C 5.0V 16Mbit DRAMs (4Mx4)
– 12 Gbits total (1440 die)
• Die are packaged in Irvine Sensor (ISC) 320 Mbit memory 
stacks
• System utilized error detection and correction 
(EDAC)
– Reed-Solomon (224,234)
• 2 “events” observed in first 9 months each with 
~100 correctable EDAC errors
– Errors occurred in differing logical block ranges
– Isolated to specific memory die row
– Errors remained even when new data was written to 
these erroneous memory locations
11
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Example: Hubble Space Telescope (HST)
Solid State Recorder (SSR) – 2 of 2
• IBM Luna ES 5.0 V Rev C die – test data prior to flight
– Heavy ions
• Events similar to in-flight anomaly observed with a LET0 of 5 
MeV*cm2/mg
• Event cleared by power cycle or device reset, but not by a rewrite 
of new data
• Denote this event as a block SEFI (Single Event Functional 
Interrupt)
– 3 die were proton single event effect (SEE) tested to proton fluences 
of 1e10 or 1e11 protons/cm2
• No block SEFIs observed: test report notes that they were 
expected due to heavy ion results
• Re-test of 100 die after anomaly observed at 1e11+ 
protons/cm2 correlated with flight observations
– Thankfully Reed-Solomon  worked fine, so no true impact to 
mission
• Proton testing pre-flight did not provide enough error 
signature coverage
12
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Application Environment
• Rule #1: Ground irradiation is a confidence test and 
not a precise risk definition process.
– The test is being performed to “bound” a problem. In other 
words,
• Test fluence levels are not meant to be the same as what a 
device will be exposed to, but to provide confidence that the risk 
will be less than X of occurring.
• Remember, X can be based on a limiting cross-section when no 
events have been observed
– Though not likely true, assume that the next particle that hits the 
DUT causes an event, so that the limit of the cross-section is ~1/F.
– It is important to remember that a test fluence of two to ten 
times a mission predicted fluence only goes so far in 
reducing risk.
• Higher levels should be considered (keeping in mind total dose 
concerns at the DUT level) for better risk reduction.
• If a mission proton fluence (of energies of interest) is 109, what 
does a test to 1010 buy?
13
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
More on POF
• Not all particles are created equal:
– Some deposit energy “on a track” as per image below 
(traditional heavy ion).
– Some interact with materials and cause secondary particles to 
deposit the energy.
• This is the traditional proton SEU concern (though direct 
ionization with low energy protons is a consideration for 
advanced technology nodes).
• This is a lesser concern for heavy ions though it shouldn’t be 
ignored.
• So what’s this have to do with fluence levels?
14
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Proton Physics
• Total nuclear production cross section
– # ions out/#protons in
• These secondary particles have a distribution of linear 
energy transfer (LET) as well as usually being of short 
range.
– These are particle kinematic effects to consider when 
establishing a proton fluence:
• Number of interactions that occur that have secondary ion 
spallations,
• Distribution of the secondary ions, and
• Risk coverage versus mission environment, sample size, 
geometry, etc…
– Is 1012 protons/cm2 a realistic choice? Approximates the 107
ions/cm2 in JESD57
Be wary of total dose or displacement damage at higher fluence levels: 
consider more samples of the DUT at lower fluence levels.
15
Energy(MeV) Sigma (cm^-2)
50 4.76E-06
100 3.89E-06
200 3.46E-06
500 5.37E-06
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Visual Protons
(courtesy R. L. Ladbury and J.-M. Lauenstein, NASA/GSFC)
16
How good are protons at
simulating heavy ions?
Silicon’s not the only culprit
In creating problems
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
And Another Thing:
Heavy-ions Come from Many Places
• Destructive proton-induced SEE seen on 
OP470
– Similar failure seen with heavy ions but at 
LETs above those attainable from usual 
proton recoils
– Problem resolved and attributed to Au 
fission fragments from Au ions knocked off 
of Au plating on part lid
• If failure not previously observed w/ heavy 
ions
– Failure mechanism would probably remain 
mysterious
– Proton rate dominate in proton dominant 
environment
• Au is not the only high-Z material in 
packaging
– Pb solder is ubiquitous
– Pt also used in some parts
• Effect likely to be important if part 
experiences severe SEE with onset at 
LET>20 MeVcm2/mg
• Effect likely not seen w/ only 1010 200-
Mev protons/cm2
Pb
Figures from T. 
Turflinger 
et al., submitted to 
IEEE Trans. on 
Nucl. Sci., 2015
17
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
And You Just Wanted a Number…
• Sorry folks, there’s no easy answer when you 
consider that:
– F is a function of (geometry, operations, sample size, and 
POF).
• Suggestions:
– Remember, it’s a bounded problem and reducing risk is 
the desired outcome.
• Risk can’t fully be eliminated, but weeding out a reasonable 
coverage of error signatures and sensitivity levels is the 
goal.
– Understand the dynamics of an accelerated beam test 
versus what you’ll be exposed to in space:
• Drives data collection and how to apply it.
• Final thought:
– Even for sensitive devices 1010 protons/cm2 isn’t enough.
18
To be presented by Kenneth A. LaBel at JEDEC JC-13 Joint Electron Device Engineering Council (JEDEC), Committee Meeting, 
Columbus, OH, September 28 to October 1, 2015.
Acknowledgements
• Melanie Berg, ASRC Space & Defense
• Jean-Marie Lauenstein, NASA/GSFC
19


Proton Particle Test Fluence: What's the Right Number?

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