Prediction Of Neutron Multiple Bits Upset Cross Section In Deep Submicron

Neutron radiation exists in the atmosphere,ground surface,nuclear explosion and other environments.The single event effect caused by neutron radiation has a great impact on the stability of aerospace electronic equipment.With the development of integrated circuit technology towards small size,the area of transistors in SRAM(Static Random-Access Memory)cell is reduced and the spacing between transistors is reduced.As a result,Multiple Bits Upset caused by single neutron radiation often occurs.The charge sharing effect is an important reason for Multiple Bits Upset caused by neutrons and other particles.The smaller the process size,the more easily the charge generated by single event effect can be collected by multiple transistor devices.The change of process size makes the charge collection range of transistor change,which affects the parameters of sensitive body extracted and the cross section of neutron single event upset.RPP(Rectangular Parallelepiped)model is widely used in the sensitive body of single event simulation,but with the decrease of process size,the error of charge collection is also increasing.In order to solve the above problems,this paper uses Sentaurus TCAD(Technology Computer Aided Design)tool to simulate the charge sharing effect and GEANT4 tool to simulate the neutron Multiple Bits Upset effect from the device circuit level and nuclear reaction level.The research work is summarized as follows:1.The device models of NMOS and PMOS transistors are established for SMIC's 40 nm bulk silicon process and calibrated with n11 ckt and p11 ckt transistors respectively.The device model of charge sharing effect is established for simulation study The simulation results show that the increase of MOSFET number will cause the decrease of the charge collected by the original MOS transistor.The influence of charge sharing decreases and increases with the increase of distance and LET value respectively.The charge sharing influence rate of NMOS decreases with the increase of distance or LET value.2.The unit layout of 6t-sram(6-transistor SRAM)is built in virtuoso tool.The threshold charge and geometry parameters of NMOS and PMOS sensitive bodies are extracted by sentaurus TCAD tool.A 4-bit × 4-bit SRAM unit detector is built in GEANT4.The influence of neutron incident energy and angle on single event upset is predicted by GEANT4 simulation tool.The results show that the ratio of Multiple Bits Upset increases first and then remains unchanged with the increase of energy,and increases with the increase of angle.3.In GEANT4,the influence of the size of the sensitive body,the distance between the sensitive bodies and the size spacing of the sensitive bodies on the prediction of the neutron single event upset cross-section is studied in GEANT4.The results show that the Multiple Bits Upset cross-section of the composite sensitive body model is larger than that of the cylinder sensitive body model.The overturning cross-section of RPP model is related to the size of the sensitive body,and the change trend of the overturning cross-section of different sensitive bodies under different energy is consistent.