Modeling and assessing the influence of linear energy transfer on multiple bit upset susceptibility

The influence of the metric of linear energy transfer （LET） on single event upset （SEU）, particularly multiple bit upset （MBU） in a hypothetical 90-nm static random access memory （SRAM） is explored. To explain the odd point of higher LET incident ion but induced lower cross section in the curve of SEU cross section, MBUs induced by incident ions 132Xe and 2~9Bi with the same LET but different energies at oblique incidence are investigated using multi-functional package for single event effect analysis （MUFPSA）. In addition, a comprehensive analytical model of the radial track structure is incorporated into MUFPSA, which is a complementation for assessing and interpreting MBU susceptibility of SRAM. The results show that （i） with the increase of incident angle, MBU multiplicity and probability each present an increasing trend; （ii） due to the higher ion relative velocity and longer range of ~ electrons, higher energy ions trigger the MBU with less probability than lower energy ions.     

重离子辐照带有ECC的65 nm SRAM器件“伪多位翻转”特性研究

为了提高纠错编码（ECC）的有效性,先进的静态随机存储器（SRAM）多采用位交错结构。但是,在没有物理版图信息的情况下,位交错设计使得从辐照测试数据中提取出多单元翻转（MCU）变得更加困难。运用Bi离子辐照带有ECC的65 nm SRAM器件,研究了该款器件在重离子辐照下的敏感性。为"伪多位翻转（FMBU）"以及MCU的数据分析提供了理论指导和帮助,完善了判别MCU的基本法则。除此之外,研究结果表明,ECC的汉明编码对于纳米器件的效果不够理想。在未来的空间应用中,需考虑更高层次的编码算法来抵抗单粒子翻转。In order to improve the robustness of error-correcting codes (ECC), modern static random access memory (SRAM) always use bit-interleaving structure. However, in the absence of physical layout information, the bit-interleaving design makes it more difficult to extract the multiple-cell upset (MCU) from the test data. In this paper, the sensitivity of Bi ion irradiation was investigated in a 65 nm technology SRAM with ECC. The experimental results provide a theoretical guidance and help for the fake multiple-bit upset (FMBU) and MCU data analyzing, which improve and perfect the basic rules extracting MCU from the test data. In addition, the results show that the performance of hamming encoding is not ideal in Nano scale SRAM. In the future of space applications, it is necessary to consider more advanced algorithms to against SEU.     

Monte Carlo evaluation of spatial multiple-bit upset sensitivity to oblique incidence

We investigate the impact of heavy ion irradiation on a hypothetical static random access memory (SRAM) device. Influences of the irradiation angle, critical charge, drain-drain spacing, and dimension of device structure on the device sensitivity have been studied. These prediction and simulated results are interpreted with MUFPSA, a Monte Carlo code based on Geant4. The results show that the orientation of ion beams and device with different critical charge exert indispensable effects on multiple-bit upsets (MBUs), and that with the decrease in spacing distance between adjacent cells or the dimension of the cells, the device is more susceptible to single event effect, especially to MBUs at oblique incidence.