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Single Event Effects in
microelectronic circuits
Author: Klemen Koselj
Advisor: Prof. Dr. Peter Križan
Agenda
• Introduction – what are Single Event Effects
(SEE) and their classification.
• Ionizing radiation environment and SEE's.
• How SEE testing is done?
– SEE testing with radiation method
– SEE testing with pulsed laser method
• Conclusion
Microelectronic circuits in
radiation environment
• The effects resulting from the interaction of
high-energy ionizing radiation with
semiconductor material can have a major
impact on the performance of space-based
and accelerator-based microelectronic
circuitry. Two categories:
– Total ionizing dose effects.
– Single Event Effects (SEE).
What is a SEE?
• Electrical disturbance in a microelectronic circuit
caused by the passage of a single ionizing particle
through semiconductor material.
• As a single high-energy particle penetrates a
circuit, it leaves behind a dense plasma track in the
form of electron-hole pairs. A circuit functional
error, or even a circuit failure, will occur if
sufficient charge from the plasma track is
collected at a sensitive circuit node.
Types of SEE
• Single-event upset (SEU) is a change of state or
transient induced by an ionizing particle such as a
cosmic ray or proton in a device.
• Single-event latch up (SEL) is a potentially
destructive condition involving parasitic circuit
elements.
• Other types (Single event burnout (SEB) –
destructive form of SEL, ...)
Types of SEE - again
• Categorization of SEE's is also possible in terms
of whether they are soft or hard errors regarding
the amount and permanency of damage made to
the device.
• Soft errors are nondestructive. They may appear as
a bit flip in a memory cell or as transients
occurring on the output of an I/O, logic, or other
support circuit. SEU is a soft error.
• Hard errors may be (but are not necessarily)
physically destructive and are permanent
functional effects. SEL and SEB are hard errors.
Ionizing radiation environment
and SEE’s
• Most problems in microelectronic circuits by
present date were observed in space-based
electronics.
• Problems in operating due to SEE’s were also
observed in avionics electronics.
• Read-out electronics in accelerator environment is
affected by high-energy ionizing radiation.
• SEE’s were observed and are significant in a
population of humans with implantable
cardioverter defibrillators. SEE’s in this case are
caused by secondary cosmic ray neutron flux.
SEE errors from the UoSAT-3
spacecraft in polar orbit
• Most SEE errors occur in
the so-called South
Atlantic Anomaly
• Errors occur because of
protons with broad energy
spectrum (energies from
keV to several hundreds of
MeV) are trapped in the
so-called Van Allen belt.
• Significant number of
errors occur at high
latitudes due to galactic
cosmic rays.
How does a SEE appear?
• Caused by a deposition of a large amount of
energy in a small sensitive volume,
typically 10 MeV energy deposition over 1
m particle path length.
• Following Bethe and Bloch the average
energy loss dE per length dx is given by
2 2 2

dE
Z
1
2
m
c

2
2 2
2
e  

 4N Are mec z
ln
  
2 
dx
A 
I
2
Energy deposition
• For highly relativistic Z = 1 particles with  ~ 1,
dE/dx=4.6 MeV/cm in silicon. Not enough for
SEE.
• For a SEE to occur slow particles ( ~ 10-2) or
particles with high Z (or a combination of both
parameters) are needed in order to produce 10
MeV energy deposition over 1 m which is
needed to produce enough charge for SEE.
• Protons can not cause SEE directly. Electrons
either.
Electron-hole pair creation
Where do particles with proper
energy deposition come from?
• Spallation reactions of neutrons and protons with
silicon 28Si(n,)25Mg, 28Si(n,p)28Al, and
28Si(p,2p)28Al all produces recoilling heavy nuclei.
• Production of silicon recoil nuclei through
electromagnetic interaction.
• 10B(n,)7Li produces an alpha particle and the
residual 7Li. (Boron is often used for doping in
semiconductor industry.)
Electron hole-pair distribution
• The electron-hole pair
distribution depends on
radial distance from the
center of the track.
• Once the electron-hole
pairs are established in the
track, the carriers can be
collected at junctions in the
Initial electron-hole density as a function of radius
structure.
from the center of ion track for various depths for
(a) 70 MeV and 250 MeV Cu ions
• Complicated drift,
diffusion and
recombination processes
are responsible for
generated charge transport.
Calculating SEE's error rates
• In the burst generation rate (BGR) model a
SEE may occur when a high-energy particle
strikes the reversed biased pn junction of a
memory cell and deposits sufficient (critical)
charge in small enough (sensitive) volume to
cause a change in memory state.
• The soft error rate (SER) is given by:
SER  
i
dN
C( Er , t ) Sf V  BGR( En , Er )
dEn
dEn
En
Burst generation rate method
• To obtain quantitative measure for soft error rate we need
to identify all important interactions of ionizing radiation
for a given environment.
• Then Qc has to be estimated. In memory cells, where
charge is used to store information (DRAM's and CCD's),
it is assumed that a sudden spontaneous 20 percent
variation in charge may cause the device to invert (from
strored '1' to '0').
• Finally we have to measure the fluxes and spectra of
radiation in environments where soft error rate is of
interest, and together with measured or calculated burst
generation rate calculate particle-induced error for each of
the important interactions.
Chip errors induced by sea-level
cosmic rays obtained with BGR
SEE rates in implantable cardioverter defibrillators were also
estimated using BGR as 4.510-12 upset/bit-hr which is well in
accordance with observations in the field.
Single event effects testing
• There are two important SEE testing
techniques nowadays:
– The tests are traditionally performed using
energetic particles produced at accelerators to
simulate the radiation environment in which
device under test will operate.
– Recently laser pulses have been used to induce
SEE's.
SEE testing with the radiation
method
• Particle accelerator testing
is the standard method
used to characterize the
sensitivity of
microelectronic circuitry
to SEE.
• The goal of SEE testing
with radiation method is to
determine the cross
section vs. the deposited
energy (known as Linear
Energy Transfer (LET))
Single event effects testing with
pulsed laser method
• Pulsed laser method is based
on the ability of laser pulses
to provide a reasonable
approximation of the
interaction between a highenergy particle and a
semiconductor.
• It provides complementary
information and some
unique characteristics and
capabilities that are
particularly useful for SEE
studies – spatial distribution.
Benefits of pulsed laser method
• The laser can be focused down and imaged to a
small spot ( 1 m). Therefore sensitivity of
individual circuit elements can be measured. This
is not easily accomplished with radiation method.
• As long as the laser intensity is below the
threshold for melting in the semiconductor, there
is no permanent damage to the material.
• There is no ionizing radiation threat, no vacuum is
required and laser tests are relatively inexpensive
compared to radiation tests.
Conclusion
• Interaction of high-energy ionizing radiation with
semiconductor material impacts the performance of
microelectronic circuitry operating in space or accelerator
environment.
• Effects of interactions with single high-energy ionizing
particles causes errors in circuit operation called Single
Event Effects - SEE. These errors can cause temporal or
permanent damage to microelectronic circuits.
• Two techniques were presented, pulsed laser and radiation
method, both intended to explore and characterize the SEE
behavior in microelectronics circuits.