SEE Mechanisms in Microelectronics

Single-event effects begin when a particle deposits charge in a sensitive volume; understanding the mechanism explains why some devices fail and others tolerate the hit.

From energy deposit to upset

When an energetic particle passes through silicon, it leaves a trail of electron-hole pairs. If that charge is collected at a sensitive node faster than the circuit can respond, the node's voltage moves and the logic state can change. The key quantity is the collected charge compared with the circuit's critical charge, the smallest charge that will cause an upset.

Neutron-specific path

Neutrons carry no charge, so they do not ionize directly. Instead a neutron collides with a nucleus in or near the device, producing recoiling charged fragments. Those fragments do the ionizing. A 14 MeV neutron can produce heavier, more energetic recoils and can open reactions that release alpha particles, so it probes a harsher part of the upset spectrum than lower-energy neutrons.

• Critical charge falls as transistors shrink
• Smaller nodes upset more easily but hold less charge each
• Multi-bit upsets grow as cells pack closer together

Design response

Hardening techniques, error-correcting codes, redundancy, and layout choices, all aim to raise effective critical charge or to catch and correct upsets. Testing quantifies how well they work under a representative beam.

Why scaling makes it harder

As transistors shrink, each storage node holds less charge, so the critical charge needed to cause an upset falls. That would suggest smaller devices upset more easily, and per bit they often do. But smaller nodes also collect charge from a smaller volume, and modern designs pack error correction and redundancy alongside. The net susceptibility is therefore a design outcome, not a foregone conclusion, which is exactly why direct measurement under a representative beam remains necessary for each new part.

This is a public overview only. It contains no classified information, no operational detail, and no weapons-design content.