Microscopic physical origin of charge traps in 3D NAND flash memories


 We performed the first-principles calculations for a nitrogen vacancy (VN) and hydrogen(H) atom in β-Si3N4 to clarify the atomistic origin of charge traps in silicon nitride (SiN) layers and charge-trapping mechanism used for 3D NAND flash memories. The present calculations showed that VN attracted H impurities and the structures where one Si dangling bond on VN is terminated by an H atom and the remaining two Si atoms form Si-Si bond (VN-H complexes) were formed in SiN layers. We investigated the electronic behavior of VN-H complexes and found that VN-H complexes act as charge traps. From our results, the atomistic origin of charge traps in SiN layers seems to be VN-H complexes.