Title :
Proton Radiation Effects on Nanocrystal Non-Volatile Memories
Author :
Verrelli, E. ; Tsoukalas, D. ; Kokkoris, M.. ; Vlastou, R.. ; Dimitrakis, P.. ; Normand, P.
Author_Institution :
Nat. Tech. Univ. of Athens, Athens
Abstract :
We report on proton radiation effects on Si-nanocrystal (Si-NCs) MOS capacitors and nMOS transistors aiming at non-volatile memory applications. Irradiation experiments were conducted on NC MOS capacitors using protons of 1.5 MeV and 6.5 MeV and on NC nMOS transistors using protons of 1.5 MeV. The range of doses investigated was ~ 1 to ~ 100 Mrad (SiO2). A 2-D layer of Si NCs with ~ 3 nm mean diameter and 1012 cm-2 surface density was successfully achieved by low-energy (1 keV) ion-beam-synthesis in thin SiO2 layers. After irradiation, programmed capacitors are found to undergo bit flip while programmed transistors are not. Charge retention measurements at room temperature for the write and erase states of irradiated and non-irradiated samples reveal that a significant memory window exists at an extrapolated time of ten years even after an irradiation dose as high as 120 Mrad (SiO2). The flat-band decay rate of the erase state in NC MOS capacitors does not depend on the irradiation-dose while the opposite occurs for the write state which is found to be directly dependent on Dit values after irradiation. These results clearly indicate that NC non-volatile memories (NVM) are promising radiation tolerant devices.
Keywords :
MOS capacitors; MOSFET; elemental semiconductors; nanostructured materials; proton effects; random-access storage; silicon; Si - Interface; Si-nanocrystal MOS capacitors; SiO2 - Interface; charge retention measurements; electron volt energy 1 keV; electron volt energy 1.5 MeV; electron volt energy 6.5 MeV; erase state; flat-band decay rate; low-energy ion-beam-synthesis; memory window; nMOS transistors; nanocrystal nonvolatile memories; proton radiation effects; surface density; write state; Aerospace electronics; Charge measurement; Current measurement; MOS capacitors; MOSFETs; Nanocrystals; Nonvolatile memory; Proton radiation effects; Temperature measurement; Time measurement; Data retention; nanocrystal memories; non-volatile memory (NVM); proton radiation effects;
Journal_Title :
Nuclear Science, IEEE Transactions on
DOI :
10.1109/TNS.2007.902365