Simulation of δ-electron Effect on Single Event Upsets in SRAMs

Key words: 
• single event effect /
• radial ionization profile /
• multiple bit upset /
• Geant4

Abstract: As the size of the transistor sensitive volume is decreased with the technology generation, the radial distribution of -electrons around the ion path has become more and more important to SEE(Single Event Effects) in semiconductor devices. Because it tends to, by causing MBU(Multiple-bit Upsets), invalidate error correcting codes which allow the device to work properly even when errors occur. In this work, Geant4 toolkit was used to simulate the radial ionization profile of heavy ions with different parameters. From the simulation,the certain rules were deduced: the higher the ion energy per nucleon, the wider the radial ionization track;for an identical energy per nucleon, the heavier the ion, the higher the electron density in track core. Then by simulating SEU(Single Event Upsets) of a 45 nm static random access memory (SRAM), effects of ion track structure on its MBU were illustrated. The maximum value of the MBU probability is determined not only by the structure of the device but also by the distribution of the -electrons generated by the incident ion. For ion energies between the top of the curve and the Bragg Peak, the MBU probability of the device decreases with the increasing LET values. For other ion energies, the probability increases as LET increasing.