Radiation-Induced Variable Retention Time in Dynamic Random Access Memories

Abstract

The effect of gamma-ray and neutron radiations on the Variable Retention Time (VRT) phenomenon occurring in Dynamic Random Access Memory (DRAM) is studied. It is shown that both ionizing radiation and non-ionizing radiation induce VRT behaviors in DRAM cells. It demonstrates that both Si/SiO2 interface states and silicon bulk defects can be a source of VRT. It is also highlighted that radiation induced VRT in DRAMs is very similar to radiation induced Dark Current Random Telegraph Signal (DC-RTS) in image sensors. Both phenomena probably share the same origin but high magnitude electric fields seem to play an important role in VRT only. Defect structural fluctuations (without change of charge state) seem to be the root cause of the observed VRT whereas processes involving trapping and emission of charge carriers are unlikely to be a source of VRT. VRT also appears to be the most probable cause of intermittent stuck bits in irradiated DRAMs.

Effects of Thermal Neutron Irradiation on a Self-Refresh DRAM

“…From static and dynamic test modes realized during a test campaign, different kinds of failures were identified. Besides the occurrence of SBUs, the tests showed permanent and temporary stuck bits, which already had been reported in several studies, presenting different fault mechanisms, being the most probable cause the irradiation impact on the variable retention time phenomenon [29], [30].…”

Comparison of Dark Current Random Telegraph Signals in Silicon and InSb-Based Photodetector Pixel Arrays

“…The second hypothesis corresponds to the involvement of a metastable defect exhibiting several possible configurations without a change of charge state [2], [5]- [7]. The existence of such defects switching spontaneously between several geometrical configurations thanks to the interaction with a phonon has been discussed in several articles [8], [32]- [34]. This hypothesis seems compatible with the signatures observed for all the devices analyzed in this article.…”

“…1) The modulation of the electron/hole pair generation rate of a generation center by another defect which would change its configuration by capturing and emitting carriers [2]- [4]. 2) Metastable generation centers switching spontaneously between several possible configurations and without involving the trapping and emission of a charge carrier [5]- [8]. The purpose of this work is to discuss the observed dc-RTS signals in several materials.…”

Electron-Induced Upsets and Stuck Bits in SDRAMs in the Jovian Environment

“…This effect has been discussed e.g. in [13]- [15] with stuck bits observed during irradiation with other particle types than electrons. ISBs discussed in these publications have, like the ones found here, long periods of time where they are not stuck.…”

“…There, a common suggested cause for the stuck bits is single particles creating leakage paths from the cell capacitor by displacement damage. In [13], as well as in [14], [15], intermittently stuck bits (ISB) are discussed, which deals with the phenomenon of bits appearing as stuck in some periods of time, when otherwise they can operate normally and return the correct value which was written to the memory cell. Stuck bits are discussed in [16] under the terminology weakened cells, where flight data and ground data are presented.…”