纳米DDR SRAM器件重离子单粒子效应试验研究

针对90 nm和65 nm DDR（双倍数率）SRAM器件,开展与纳米尺度SRAM单粒子效应相关性的试验研究。分析了特征尺寸、测试图形、离子入射角度、工作电压等不同试验条件对单粒子翻转（SEU）的影响和效应规律,并对现有试验方法的可行性进行了分析。研究表明:特征尺寸减小导致翻转截面降低,测试图形和工作电压对器件单粒子翻转截面影响不大;随着入射角度增加,多位翻转的增加导致器件SEU截面有所增大;余弦倾角的试验方法对于纳米器件的适用性与离子种类和线性能量转移（LET）值相关,具有很大的局限性。     

静态单粒子翻转截面的获取及分类

 为了评估静态随机访问存储器(SRAM)型现场可编程门阵列(FPGA)器件的单粒子效应,寻求单粒子翻转敏感部位,以XCV300PQ240为实验样品,利用重离子辐照装置详细测试了该器件的静态翻转截面,并根据配置存储单元用途的不同,对翻转数据进行了分类。结果表明：SRAM型FPGA的内部存储单元对单粒子翻转效应十分敏感;配置存储器翻转主要由查找表(LUT)及互连线资控制位造成,这两者的翻转占总翻转数的97.46%;配置存储器中各类资源的单粒子翻转(SEU)敏感性并不一致,输入输出端口(IOB)控制位和LUT的单粒子翻转的敏感性远高于其它几类资源,但LUT在配置存储器中占有很大比例,在加固时应予以重点考虑。     

静态随机存储器单粒子翻转效应三维数值模拟

针对特征尺寸为1.5 μm的国产静态随机存储器（SRAM）,构建了三维SRAM存储单元模型,并对重离子引起的SRAM单粒子翻转效应进行了数值模拟.计算并分析了单粒子引起的单粒子翻转和电荷收集的物理图像,得到了SRAM器件的单粒子翻转截面曲线.单粒子翻转的数值模拟结果与重离子微束、重离子宽束实验结果比较一致,表明所建立的三维器件模型可以用来研究SRAM器件的单粒子翻转效应. 关键词： 三维数值模拟 单粒子翻转 微束 宽束     

总剂量辐射环境中的静态随机存储器功能失效模式研究

本文对静态随机存储器 (SRAM) 总剂量辐射引起的功能失效进行了六种不同测试图形下的测试. 利用不同测试图形覆盖的出错模式不同, 通过对比一定累积剂量下同一器件不同测试图形测试结果的差异, 以及对失效存储单元单独进行测试, 研究了总剂量辐照引起的SRAM器件功能失效模式. 研究表明: 器件的功能失效模式为数据保存错误 (Data retention fault) 且数据保存时间具有离散性, 引起数据保存错误的SRAM功能模块为存储单元. 通过对存储单元建立简化的等效电路图, 分析了造成存储单元数据保存错误以及保存时间离散性的原因, 并讨论了该失效模式对SRAM总剂量辐射功能测试方法的影响. 关键词： 静态随机存储器 功能失效 测试图形 数据保存错误     

累积剂量影响静态随机存储器单粒子效应敏感性研究

本文利用60Coγ源和兰州重离子加速器,开展不同累积剂量下,静态随机存储器(static random access memory,SRAM)单粒子效应敏感性研究,获取不同累积剂量下SRAM器件单粒子效应敏感性的变化趋势,分析其辐照损伤机理.研究表明,随着累积剂量的增加,SRAM器件漏电流增大,影响存储单元低电平保持电压、高电平下降时间等参数,导致"反印记效应".研究结果为空间辐射环境中宇航器件的可靠性分析提供技术支持.     

深亚微米SRAM质子单粒子翻转实验研究

宇航半导体器件运行在一个复杂的空间辐射环境中,质子是空间辐射环境中粒子的重要组成部分,因而质子在半导体器件中导致的辐射效应一直受到国内外的关注。利用兰州重离子加速器(Heavy Ion Research Facility In Lanzhou) 加速出的H2 分子打靶产生能量为10 MeV 的质子,研究了特征尺寸为0.5/0.35/0.15 μm体硅和绝缘体上硅(SOI) 工艺静态随机存储器(SRAM) 的质子单粒子翻转敏感性,这也是首次在该装置上开展的质子单粒子翻转实验研究。实验结果表明特征尺寸为亚微米的SOI 工艺SRAM器件对质子单粒子翻转不敏感,但随着器件特征尺寸的减小和工作电压的降低,SOI 工艺SRAM器件对质子单粒子翻转越来越敏感;特征尺寸为深亚微米的体硅工艺SRAM器件单粒子翻转截面随入射质子能量变化明显,存在发生翻转的质子能量阈值,CREME-MC模拟结果表明质子在深亚微米的体硅工艺SRAM器件中通过质子核反应导致单粒子翻转。Microelectronic devices are used in a harsh radiation environment for space missions. Among all the reliability issues concerned, proton induced single event upset (SEU) is becoming more and more noticeable for semiconductor components exposed on space. In this work, an experimental research of SEU induced by 10 MeV proton for static random access memory (SRAM) of 0.5, 0.35 and 0.15 m feature size is carried out on HeavyIon Research Facility in Lanzhou for the rst time. The experimental results show that proton induced SEUs in submicron and deep-submicron (SRAMs) are dominated by secondary ions generated by proton nuclear reaction events. The silicon-on-insulator SRAMs characters natural radiation-hardened SEU by proton. For the deep-submicron bulk-silicon technology SRAM, the proton SEU cross section is closely related to the proton energy and there is a threshold energy for the SEU occurrence by proton indirect ionization. CREME-MC simulation indicates that the SEU events in deep-submicron SRAM are induced by the proton nuclear reaction.     

随机静态存储器低能中子单粒子翻转效应

 建立了中子单粒子翻转可视化分析方法,对不同特征尺寸（0.13~1.50 μm）CMOS工艺商用随机静态存储器(SRAM)器件开展了反应堆中子单粒子翻转效应的实验研究,获得了SRAM器件的裂变谱中子单粒子翻转截面随特征尺寸变化的变化趋势。研究结果表明:SRAM器件的特征尺寸越小,其对低能中子导致的单粒子翻转的敏感性越高。     

基于中国散裂中子源的商用静态随机存取存储器中子单粒子效应实验研究

利用中国散裂中子源反角白光中子束线开展13款商用静态随机存取存储器的中子单粒子效应实验.研究了测试图形、特征尺寸和版图工艺差异对单粒子效应的影响.结果表明测试图形对器件的单粒子翻转截面影响不大,但对部分器件的多单元翻转占比有较大的影响;特征尺寸对器件单粒子翻转截面的影响没有明显的规律,但对多单元翻转的影响规律明显,多单元翻转占比和最大位数都随着特征尺寸的降低而增大;器件版图工艺差异对器件的单粒子翻转截面和多单元翻转占比都有较大的影响.此外,通过与高原辐照实验结果对比,发现在反角白光中子源获得的多单元翻转占比小于高原辐照实验的结果,其原因是反角白光中子源实验中,中子的最高能量和高能成分占比偏小,且中子束流只有垂直入射.因此,利用反角白光中子源评估器件的大气中子单粒子效应时可能会低估多单元翻转情况.本文的结果可为研究者利用反角白光中子源开展相关研究提供参考.     

基于55 nm DICE结构的单粒子翻转效应模拟研究

单粒子翻转(single event upset, SEU)是器件在辐照空间中应用的关键难题,本文以55 nm加固锁存单元为研究载体,通过三维数值模拟方法,获得了重离子不同入射条件下的线性能量转移(linear energy transfer, LET)阈值和电压脉冲变化曲线,研究了双互锁存储单元(dual interlockded storage cell, DICE)的抗辐照性能和其在不同入射条件下的SEU效应.研究表明,低LET值的粒子以小倾斜角入射器件时,降低了器件间的总电荷收集量,使得主器件节点的电压峰值和电压脉宽最小,器件SEU敏感性最低;由于空穴与电子迁移率的差异,导致DICE锁存器中Nhit的入射角敏感性远大于Phit;合理调节晶体管间距可以削弱电荷共享效应,使得从器件总电荷收集量减小,仿真计算得到此工艺下晶体管间距不能小于1.2μm.相关仿真结果可为DICE锁存单元单粒子效应的物理机制研究和加固技术提供理论依据和数据支持,有助于加快存储器件在宇航领域的应用步伐.     

累积辐照影响静态随机存储器单粒子翻转敏感性的仿真研究

基于解析分析对比了大尺寸与深亚微米尺度下静态随机存取存储器(static random access memory, SRAM)单元单粒子翻转敏感性的表征值及引入累积辐照后的变化趋势. 同时借助仿真模拟计算了0.18 μm工艺对应的六管SRAM单元在对应不同累积剂量情况下, 离子分别入射不同中心单管时的电学响应变化, 计算结果与解析分析所得推论相一致, 即只有当累积辐照阶段与单粒子作用阶段存储相反数值时, SRAM单元的单粒子翻转敏感性才会增强. 关键词： 累积辐照 单粒子翻转 静态随机存储器 器件仿真     

Ionizing radiation effect on single event upset sensitivity of ferroelectric random access memory

The impact of ionizing radiation effect on single event upset(SEU) sensitivity of ferroelectric random access memory(FRAM) is studied in this work. The test specimens were firstly subjected to ~(60)Co γ-ray and then the SEU evaluation was conducted using ~(209)Bi ions. As a result of TID-induced fatigue-like and imprint-like phenomena of the ferroelectric material, the SEU cross sections of the post-irradiated devices shift substantially. Different trends of SEU cross section with elevated dose were also found, depending on whether the same or complementary test pattern was employed during the TID exposure and the SEU measurement.     

Synergistic effect of total ionizing dose on single event effect induced by pulsed laser microbeam on SiGe heterojunction bipolar transistor

The synergistic effect of total ionizing dose(TID) on single event effect(SEE) in SiGe heterojunction bipolar transistor(HBT) is investigated in a series of experiments. The SiGe HBTs after being exposed to 60 Co g irradiation are struck by pulsed laser to simulate SEE. The SEE transient currents and collected charges of the un-irradiated device are compared with those of the devices which are irradiated at high and low dose rate with various biases. The results show that the SEE damage to un-irradiated device is more serious than that to irradiated SiGe HBT at a low applied voltage of laser test. In addition, the g irradiations at forward and all-grounded bias have an obvious influence on SEE in the SiGe HBT, but the synergistic effect after cutting off the g irradiation is not significant. The influence of positive oxide-trap charges induced by TID on the distortion of electric field in SEE is the major factor of the synergistic effect. Moreover, the recombination of interface traps also plays a role in charge collection.     

中国散裂中子源在大气中子单粒子效应研究中的应用评估

由于缺少可用的散裂中子源,多年来我国在大气中子单粒子效应方面主要依靠模拟仿真和单能中子试验的方式开展研究.随着中国散裂中子源(CSNS)通过国家验收,基于CSNS开展大气中子单粒子效应研究成为可能.本文利用CSNS反角白光中子源开展多款静态随机存取存储器器件的中子单粒子效应试验,并与早期开展的高原大气试验结果进行对比,对CSNS在大气中子单粒子效应研究中的应用进行评估.结果表明,相同器件在CSNS反角白光中子源测得的单粒子翻转截面小于大气试验的结果,且不同器件的翻转截面与特征尺寸没有明显的单调关系.分析得到前者由于CSNS反角白光中子谱偏软;后者由于特征尺寸降低导致的临界电荷变小和灵敏体积变小对截面的贡献是竞争关系.针对截面偏小的问题,根据能谱差异分析了中子能量阈值对器件翻转截面的影响,发现能量阈值取12MeV进行计算时,器件在CSNS反角白光中子源和高原大气中子环境中能够得到较一致的截面.研究结果表明CSNS反角白光中子源能够用于加速大气中子单粒子效应试验.考虑到CSNS的运行功率正在逐步提高,且多条规划中的白光中子束线与大气中子能谱更为接近,预期未来CSNS将能更好地应用于大气中子单粒子效应研究.     

半导体器件单粒子效应的加速器模拟实验

 着重描述了应用加速器开展半导体器件的单粒子效应实验研究的方法。采用金箔散射法可以降低加速器束流几个量级，从而满足半导体器件单粒子效应实验的要求。研制的弱流质子束流测量系统和建立的质子注量均匀性测量方法解决了质子注量的准确测量问题。实验测得静态随机存取存储器的质子单粒子翻转截面为10^-7 cm²·bit^-11量级，单粒子翻转重离子LET阈值为4～8MeV·cm²/mg，重离子单粒子翻转饱和截面为10^-7 cm²·bit^-1量级。     

Impact of incident direction on neutron-induced single-bit and multiple-cell upsets in 14 nm FinFET and 65 nm planar SRAMs

Based on the BL09 terminal of China Spallation Neutron Source (CSNS), single event upset (SEU) cross sections of 14 nm fin field-effect transistor (FinFET) and 65 nm quad data rate (QDR) static random-access memories (SRAMs) are obtained under different incident directions of neutrons: front, back and side. It is found that, for both technology nodes, the "worst direction" corresponds to the case that neutrons traverse package and metallization before reaching the sensitive volume. The SEU cross section under the worst direction is 1.7-4.7 times higher than those under other incident directions. While for multiple-cell upset (MCU) sensitivity, side incidence is the worst direction, with the highest MCU ratio. The largest MCU for the 14 nm FinFET SRAM involves 8 bits. Monte-Carlo simulations are further performed to reveal the characteristics of neutron induced secondary ions and understand the inner mechanisms.     

（n,xnγ）反应截面测量的实验本底改进研究

瞬发γ射线法测量（n,xnγ）反应截面实验中,在线的实验本底对测量结果影响显著,是影响测量结果的关键因素。为了达到降低在线实验本底一个量级的目标,通过蒙特卡罗模拟程序给出了屏蔽体和准直器的改进方案,最终选取的屏蔽方案:在原有屏蔽体上加厚30 cm（C₂H₄）n+9 cmPb,原屏蔽墙加厚54 cm重混凝土,再在屏蔽体和屏蔽墙上共同加厚2 cm厚的铅（Pb）;准直孔开孔形状在圆柱形、圆锥形和对称双锥形这三种方案中准直效果和能量单一性方面对称双锥形准直孔最好。在屏蔽体改造完成后,利用尺寸为φ5.08cm×5.08 cm型液体闪烁体探测器（BC501）测量了改造后距准直孔右方径向距离70 cm处透射出来的中子和γ射线的相对强度,在扣除无束流天然本底后,有束流的中子本底降低了7.75倍,γ本底降低了38.5倍,改造效果达到了测量要求。In the experiment of measuring (n,xnγ) reaction cross section with prompt γ ray method, the experiment background has a significant influence on the result and is the key factor. In order to achieve the goal of reducing a certain amount of the experiment background, the improvement scheme of shield and collimator was given through Monte Carlo method and the shielding scheme was finally selected: add 30 cm(C₂H₄)n+9 cm Pb on the original shield, 54 cm heavy concrete on the original shield wall and then 2 cm thick lead(Pb) on the shield and shield wall. The collimation effect and energy uniformity of symmetrical double cone collimation hole are the best among cylindrical, conical, and symmetrical double cone. After the completion of the transformation of shield, the relative intensities of the transmitted neutron and γ rays from the 70 cm in right radial of the transformed collimation hole were measured with ?5.08 cm×5.08 cm type liquid scintillator detector(BC501). After deducting the natural background of no beam current, the neutron background of the beam current is reduced by 7.75 times and the γ background is reduced by 38.5 times, which meets the requirement.     

Effects of Total-Ionizing-Dose Irradiation on Single-Event Burnout for Commercial Enhancement-Mode AlGaN/GaN High-Electron Mobility Transistors

We investigate the synergism effect of total ionizing dose(TID) on single-event burnout(SEB) for commercial enhancement-mode Al Ga N/Ga N high-electron mobility transistors. Our experimental results show that the slight degradation of devices caused by gamma rays can affect the stability of the devices during the impact of high energy particles. During heavy ion irradiation, the safe working values of drain voltage are significantly reduced for devices which have already been irradiated by ~(60)Co gamma rays before. This could be attributed to more charges trapped caused by ~(60)Co gamma rays, which make Ga N devices more vulnerable to SEB. Moreover, the electrical parameters of Ga N devices after ~(60)Co gamma and heavy-ion irradiations are presented, such as the output characteristic curve, effective threshold voltages, and leakage current of drain. These results demonstrate that the synergistic effect of TID on SEB for Ga N power devices does in fact exist.