Single event upset

A single event upset (SEU) is a change of state caused by one single ionizing particle (ions, electrons, photons...) striking a sensitive node in a micro-electronic device, such as in a microprocessor, semiconductor memory, or power transistors. The state change is a result of the free charge created by ionization 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.

The SEU itself is not considered permanently damaging to the transistor's or circuits' functionality unlike the case of single event latchup (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.

Single event upsets were first described during above ground nuclear testing, 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 1973. In 1978, the first evidence of soft errors from alpha particles in packaging materials was described by Timothy C. May and M.H. Woods. In 1979, James Ziegler of IBM, along with W. Lanford of Yale, first described the mechanism whereby a sea level cosmic ray could cause a single event upset in electronics.

Terrestrial SEU 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 devices in the atmosphere.

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