Single event effect

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The term Single Event Effect ( SEE ) is the generic term for effects that can be triggered in semiconductor components by the impact or the passage of a particle of ionizing radiation . These radiations include B. Alpha radiation , neutron radiation and cosmic radiation . SEEs are relevant in particular in the field of in aviation and aerospace used microelectronics , as in higher areas of the earth's atmosphere and especially in outer space increased radiation intensity prevails.

Types of single event effects

Basically, two types of SEEs can be distinguished: SEEs that cause permanent damage (so-called hard errors ) and those that only cause temporary malfunctions (so-called soft errors ). The main types of SEEs are listed below.

  • Single Event Latchup (SEL): A SEL leads to the ignition of a parasiticthyristorand thus ashort circuitin a semiconductor component . This can lead to the destruction of the affected component. An SEL can be eliminated by switching the component off and then on again in good time.
  • Single Event Upset (SEU): This effect is the "flipping" of a bit ( English bitflip) or the change in the state of a digital circuit. Depending on the location and time of the SEU, different errors can occur (e.g. changing the content of amemory cell, errors in the programflow ofa computer). An SEU does not cause permanent damage to the affected component. If an SEU leads to the complete failure of a system (e.g.computer crash), this is also referred to as a Single Event Functional Interrupt (SEFI). SEUs can alsooccuratsea ​​level. Here they are mostly caused byradioactivecontamination in the housing material of a component and the resulting alpha radiation.
  • Single Event Transient (SET): This effect manifests itself in a brief change in the signal level in an electronic circuit ( glitch ). This can also lead to various malfunctions, but does not cause permanent damage to the affected component.
  • Single Event Burnout (SEB). An SEB causes an excessive current in the area of ​​the drain-source path of a power MOSFET , which leads to the destruction of the component.
  • Single Event Gate Rupture (SEGR): SEGR describes the destruction of the gate dielectric in power MOSFETs. Just like the SEB, this effect leads to the failure of the affected component.

SEE probability

The likelihood of an SEE occurring in a particular component or assembly depends essentially on two factors:

  1. Used semiconductor technology . Different semiconductor technologies are susceptible to SEEs differently. The particle energy to be transferred to the semiconductor material, from which an SEE can occur in a component, is referred to as (for the different types of SEEs), where LET stands for linear energy transfer and the index th stands for threshold (German: Schwelle, Schwellwert ). For this purpose, MeV · cm² / mg (based on Si for MOS semiconductor components) is usually used as the unit of measurement .
  2. Radiation intensity. The intensity of the radiation to which a component is exposed can vary greatly depending on the location and time of use. For satellites , the respective orbit is particularly decisive here. Furthermore, in times of increased solar activity ( solar flares ), a higher SEE rate can be expected.

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