A4 Damage from Ionizing Radiation

Topic

When an energetic particle passes through this semiconductor material, it causes displacement damage to the material's crystal lattice: as the particle collides with the lattice atoms along its path, it knocks some of them out of their original positions, leaving behind point defects in the crystal lattice. If the particle traverses the material with higher energy, this displacement damage results in a higher density of defects along its entire path.

According to the Messenger-Spratt relationship, this defect density—resulting from the displacement damage—degrades the carrier lifetime of the semiconductor material (a parameter described in greater detail by another model in this set): each additional point defect introduced into the lattice acts as an additional recombination center where a minority carrier can recombine sooner than it would in a defect-free lattice, thereby shortening the carrier lifetime. Consequently, a higher defect density leads to an even shorter carrier lifetime, in accordance with the Messenger-Spratt relationship.

For this reason, the model—which began by addressing displacement damage and the resulting degradation of carrier lifetime—also describes a second failure mechanism distinct from accumulated displacement damage. In this mechanism, as the energetic particle passes through a memory node within the semiconductor material, it deposits charge along its path; when this deposited charge exceeds the specific critical charge of that memory node, the charge alone—without the need for any additional accumulated displacement damage—is sufficient to flip the logical state stored in the node, causing a Single Event Upset (SEU). Conversely, if the charge deposited by the energetic particle remains below the memory node's critical charge, the node retains its stored logical state without experiencing a single-event upset—even though the displacement damage left in the particle's wake continues to cumulatively degrade the carrier lifetime of the semiconductor material.

ID:4510