A single-event upset (SEU), also known as a single-event error (SEE), is a change of state caused by one single ionizing particle (e.g. ions, electrons, photons) striking a sensitive node in a live micro-electronic device, such as in a

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

semiconductor memory Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a si ...

, or power

transistors A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

. The state change is a result of the free charge created by

ionization Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive Electric charge, charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged at ...

in or close to an important node of a logic element (e.g. memory "bit"). The error in device output or operation caused as a result of the strike is called an SEU or a

soft error In electronics and computing, a soft error is a type of error where a signal or datum is wrong. Errors may be caused by a defect, usually understood either to be a mistake in design or construction, or a broken component. A soft error is also a ...

. The SEU itself is not considered permanently damaging to the transistors' or circuits' functionality, unlike the case of single-event latch-up (SEL), single-event gate rupture (SEGR), or single-event burnout (SEB). These are all examples of a general class of radiation effects in electronic devices called ''single-event effects'' (SEEs).

History

Single-event upsets were first described during above-ground

nuclear testing Nuclear weapons tests are experiments carried out to determine the performance of nuclear weapons and the effects of Nuclear explosion, their explosion. Nuclear testing is a sensitive political issue. Governments have often performed tests to si ...

, from 1954 to 1957, when many anomalies were observed in electronic monitoring equipment. Further problems were observed in space electronics during the 1960s, although it was difficult to separate soft failures from other forms of interference. In 1972, a Hughes satellite experienced an upset where the communication with the satellite was lost for 96 seconds and then recaptured. Scientists Dr. Edward C. Smith, Al Holman, and Dr. Dan Binder explained the anomaly as a single-event upset (SEU) and published the first SEU paper in the '' IEEE Transactions on Nuclear Science'' journal in 1975. In 1978, the first evidence of

s from

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

s in packaging materials was described by Timothy C. May and M.H. Woods. In 1979, James Ziegler of

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

, along with W. Lanford of

Yale Yale University is a private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the third-oldest institution of higher education in the United States, and one of the nine colonial colleges ch ...

, first described the mechanism whereby a sea-level

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

could cause a single-event upset in electronics. 1979 also saw the world's first heavy ion "single-event effects" test at a particle accelerator facility, conducted at Lawrence Berkeley National Laboratory'
88-Inch Cyclotron
and

Bevatron The Bevatron was a particle accelerator — specifically, a Weak focusing, weak-focusing proton synchrotron — located at Lawrence Berkeley National Laboratory, U.S., which began operations in 1954. The antiproton was discovered there in ...

Cause

Terrestrial SEUs arise due to cosmic particles colliding with atoms in the atmosphere, creating cascades or showers of neutrons and protons, which in turn may interact with electronic circuits. At deep sub-micron geometries, this affects

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

devices in the atmosphere. In space, high-energy ionizing particles exist as part of the natural background, referred to as galactic

cosmic rays Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar ...

(GCRs).

Solar particle event In solar physics, a solar particle event (SPE), also known as a solar energetic particle event or solar radiation storm, is a solar phenomenon which occurs when particles emitted by the Sun, mostly protons, become accelerated either in the Sun's ...

s and high-energy protons trapped in the Earth's

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...

( Van Allen radiation belts) exacerbate this problem. The high energies associated with the phenomenon in the space particle environment generally render increased spacecraft shielding useless in terms of eliminating SEUs and catastrophic single-event phenomena (e.g. destructive latch-up). Secondary atmospheric neutrons generated by

can also have sufficiently high energy for producing SEUs in electronics on aircraft flights over the poles or at high altitudes. Trace amounts of

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

elements in chip packages also lead to SEUs.

Testing for SEU sensitivity

The sensitivity of a device to SEU can be empirically estimated by placing a test device in a

particle In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...

stream at a

cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...

or other

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

facility. This particular test methodology is especially useful for predicting the SER (soft error rate) in known space environments but can be problematic for estimating terrestrial SER from neutrons. In this case, a large number of parts must be evaluated, possibly at different altitudes, to find the actual rate of upset. Another way to empirically estimate SEU tolerance is to use a chamber shielded from radiation, with a known radiation source, such as

Caesium-137 Caesium-137 (), cesium-137 (US), or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nucle ...

. When testing

s for SEU, the software used to exercise the device must also be evaluated to determine which sections of the device were activated when SEUs occurred.

SEUs and circuit design

By definition, SEUs do not destroy the circuits involved, but they can cause errors. In space-based microprocessors, one of the most vulnerable portions is often the 1st and 2nd-level cache memories, because these must be very small and have very high speed, which means that they do not hold much charge. Often these caches are disabled if terrestrial designs are being configured to survive SEUs. Another point of vulnerability is the state machine in the microprocessor control, because of the risk of entering "dead" states (with no exits), however, these circuits must drive the entire processor, so they have relatively large transistors to provide relatively large electric currents and are not as vulnerable as one might think. Another vulnerable processor component is RAM, and more specifically

static RAM Static random-access memory (static RAM or SRAM) is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM is volatile memory; data is lost when power is removed. The ''static'' qualifier differ ...

(SRAM) used in cache memories. SRAM memories are usually designed with transistor sizes close to the minimum allowed by technology to allocate the maximum number of bits per unit area. Small transistor sizes and high bit density make memories one of the most susceptible components to SEUs. To ensure resilience to SEUs, often an error correcting memory is used, together with circuitry to periodically read (leading to correction) or scrub (if reading does not lead to correction) the memory of errors, before the errors overwhelm the error-correcting circuitry. In digital and analog circuits, a single event may cause one or more voltages pulses (i.e. glitches) to propagate through the circuit, in which case it is referred to as a single-event transient (SET). Since the propagating pulse is not technically a change of "state" as in a memory SEU, one should differentiate between SET and SEU. If a SET propagates through digital circuitry and results in an incorrect value being latched in a sequential logic unit, it is then considered an SEU. Hardware problems can also occur for related reasons. Under certain circumstances (of both circuit design, process design, and particle properties) a "

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

thyristor A thyristor (, from a combination of Greek language ''θύρα'', meaning "door" or "valve", and ''transistor'' ) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage ...

inherent to CMOS designs can be activated, effectively causing an apparent short-circuit from power to ground. This condition is referred to as '' latch-up'', and in absence of constructional countermeasures, often destroys the device due to

thermal runaway Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing Thermal energy, energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the cond ...

. Most manufacturers design to prevent latch-up and test their products to ensure that latch-up does not occur from atmospheric particle strikes. In order to prevent latch-up in space,

epitaxial Epitaxy (prefix ''epi-'' means "on top of”) is a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited cry ...

substrates,

silicon on insulator In semiconductor manufacturing, silicon on insulator (SOI) technology is fabrication of silicon semiconductor devices in a layered silicon–insulator–silicon substrate, to reduce parasitic capacitance within the device, thereby improving perf ...

(SOI) or

silicon on sapphire Silicon on sapphire (SOS) is a hetero-epitaxial process for metal–oxide–semiconductor (MOS) integrated circuit (IC) manufacturing that consists of a thin layer (typically thinner than 0.6 μm) of silicon grown on a sapphire () wafer. S ...

(SOS) are often used to further reduce or eliminate the susceptibility.

Notable SEU

* In the 2003 elections in

Brussels Brussels, officially the Brussels-Capital Region, (All text and all but one graphic show the English name as Brussels-Capital Region.) is a Communities, regions and language areas of Belgium#Regions, region of Belgium comprising #Municipalit ...

's municipality

Schaerbeek (French language, French, ; former History of Dutch orthography, Dutch spelling) or (modern Dutch language, Dutch, ) is one of the List of municipalities of the Brussels-Capital Region, 19 municipalities of the Brussels, Brussels-Capital Reg ...

(

Belgium Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...

), an anomalous recorded number of votes triggered an investigation that concluded an SEU was responsible for giving a candidate named

Maria Vindevoghel Maria Vindevoghel (born 11 October 1957) is a Belgian shop steward and politician affiliated with the Workers' Party of Belgium. Biography Maria Vindevoghel was born in Waregem, Waregem, Belgium, and grew up in a primarily farming family in We ...

4,096 extra votes. The possibility of a single-event upset is suggested by the difference in votes being equivalent to a power of two, . * On October 7, 2008,

Qantas Flight 72 Qantas ( ), formally Qantas Airways Limited, is the flag carrier of Australia, and the largest airline by fleet size, international flights, and international destinations in Australia and List of largest airlines in Oceania, Oceania. A foundi ...

at 37,000 feet, one of the plane's three air data inertial reference units had a failure, causing incorrect data to be sent to the plane's flight control systems. This caused pitch-downs and caused severe injuries to crew and passengers. All potential causes were found to be "unlikely," or "very unlikely," except for an SEU, whose likelihood couldn't be estimated.The Invisible Neutron Threat (2012), Target 4 Flight Path 30L Publications, Los Alamos National Laboratory
/ref>

History

Cause

Testing for SEU sensitivity

SEUs and circuit design

Notable SEU

See also

References

Further reading