Study Of Single Event Upset In SOI SRAMs Based On Heavy Ion Accelerator

Silicon on insulator(SOI) devices have more unique advantages in space electronic systems requiring a high reliability and immunity to irradiations. However, with downscaling of feature size and increasing of integration, the development of SOI technology brings about underlying reliability issues which influence the radiation-hardened characteristics of SOI circuits. The study of single event effects for SOI technology devices has received growing attention. In this paper, the SOI static random access memories(SRAMs) with 0.5/0.35/0.18 μm are irradiated using C, Kr, Sn, Xe, Bi ions and proton of initial energy 7.0, 25.0, 3.7, 19.5, 9.5 and 9.7 Me V/u, respectively. The influences of edge effects, nuclear reaction and accumulated irradiation of heavy ions on the SEU sensitivity of SOI SRAMs are investigated. At the same time the thorough analysis for the experimental results are carried on by Geant4 and CREME-MC simulations. The experimental results and computer simulation show that the SEU sensitivity of SOI SRAMs is closely related to the incident angle, nuclear reaction and accumulated irradiation of heavy ions. This investigation provides an important reference for the radiation-hardened design of SOI technology. Main conclusions are as follows,(1) An experimental investigation of SEU susceptibility at tilted incidence of heavy ions was performed. The 86 Kr ion experimental results show that the differences of SEU cross sections between tilted incidence and normal incidence at equivalent effective linear energy transfer(LET) were 21% and 57% for the SOI SRAMs with 0.5 μm and 0.18 μm feature size, respectively. The difference of SEU cross sections raised dramatically with increasing tilted angle for SOI SRAM of deep-submicron technology. The result of CRèME-MC simulation for tilted incidence indicates that the energy deposition spectrum in the sensitive volume has a substantial tail extending into the low energy region. The experimental results show that the influence of edge effects on SEU susceptibility cannot be ignored in particular with device scaling down for SOI SRAM.(2) An investigation of SEU response to nuclear reaction is conducted for SOI SRAMs. The proton experimental results show that SEUs in submicron SOI SRAMs are dominated by secondary ions generated by proton nuclear reaction events. The heavy-ion results show an unexpected phenomenon that below the threshold LET of SOI SRAM, the SEU cross sections decrease 70% with the increase of 12 C ion LET from 1.7 to 2.9 Me V·cm2/mg, i.e., the SEU cross sections increase with the increase of 12 C ion energy. The Geant4 simulation confirms that secondary heavy ions produced by nuclear reactions are closely related to primary heavy ion energy and dominate the SEU occurrences in the sub-threshold LET region. The SEU cross sections obtained by Geant4 simulation match well with the experimental SEU cross sections at same 12 C ion energy. The presence of energy dependence of SEU for heavy ions with low LET will challenge current methods for evaluating the threshold LET and the LET as an appropriate metric to describe the SEU sensitivity.(3) An experiment was conducted to investigate the synergistic effects of heavy-ion accumulated irradiation on the SEU vulnerability of SOI SRAM. Large amounts of heavy-ion accumulated irradiation influence the SEU sensitivity and static current for SOI SRAMs. The qualitative analysis of results demonstrate that the influence of heavy-ion accumulated irradiation on SEU sensitive is attributed to the memory imprint effects and the parasitic bipolar effects. During at accumulated irradiation, heavy ions also induce the upsets of memory cell. There is the difference of synergistic effects between heavy-ion accumulated dose irradiation and gamma irradiation on SEU sensitivity.