Neutron-induced single event upset simulation in Geant4 for three-dimensional die-stacked SRAM

Three-dimensional integrated circuits(3D ICs)have entered into the mainstream due to their high performance,high integration,and low power consumption.When used in atmospheric environments,3D ICs are irradiated inevitably by neutrons.In this paper,a 3D die-stacked SRAM device is constructed based on a real planar SRAM device.Then,the single event upsets(SEUs)caused by neutrons with different energies are studied by the Monte Carlo method.The SEU cross-sections for each die and for the whole three-layer die-stacked SRAM device is obtained for neutrons with energy ranging from 1 MeV to 1000 MeV.The results indicate that the variation trend of the SEU cross-section for every single die and for the entire die-stacked device is consistent,but the specific values are different.The SEU cross-section is shown to be dependent on the threshold of linear energy transfer(LETth)and thickness of the sensitive volume(Tsv).The secondary particle distribution and energy deposition are analyzed,and the internal mechanism that is responsible for this difference is illustrated.Besides,the ratio and patterns of multiple bit upset(MBU)caused by neutrons with different energies are also presented.This work is helpful for the aerospace IC designers to understand the SEU mechanism of 3D ICs caused by neutrons irradiation.     

重离子辐照引起磁性隧道结功能失效类型及机理研究

重点研究了磁性隧道结(MTJ)的电学性能受离子注量影响的物理规律。实验首次发现了高能Ta离子辐射损伤导致MTJ电学功能失效的现象,主要失效模式为:高、低电阻态失效,其中79.9%的功能失效为高电阻态失效。计算表明,单个10.9 MeV/u的Ta离子辐照引入的损伤无法导致MTJ宏观电学功能失效。结合理论计算与Monte Carlo模拟分析,MTJ中的绝缘势垒层与铁磁薄膜的损伤是出现高、低电阻态失效的内因。