Dependence of single event upsets sensitivity of low energy proton on test factors in 65 nm SRAM

In order to accurately predict the single event upsets(SEU) rate of on-orbit proton, the influence of the proton energy distribution, incident angle, supply voltage, and test pattern on the height, width, and position of SEU peak of low energy protons(LEP) in 65 nm static random access memory(SRAM) are quantitatively evaluated and analyzed based on LEP testing data and Monte Carlo simulation. The results show that different initial proton energies used to degrade the beam energy will bring about the difference in the energy distribution of average proton energy at the surface and sensitive region of the device under test(DUT), which further leads to significant differences including the height of SEU peak and the threshold energy of SEU. Using the lowest initial proton energy is extremely important for SEU testing with low energy protons. The proton energy corresponding to the SEU peak shifts to higher average proton energies with the increase of the tilt angle, and the SEU peaks also increase significantly. The reduction of supply voltage lowers the critical charge of SEU, leading to the increase of LEP SEU cross section. For standard 6-transitor SRAM with bit-interleaving technology,SEU peak does not show clear dependence on three test patterns of logical checkerboard 55 H, all "1", and all "0". It should be noted that all the SEUs in 65 nm SRAM are single cell upset in LEP testing due to proton's low linear energy transfer(LET) value.     

Calculation of LET in SEE simulation by pulsed laser

A key point in SEE (Single Event Effect) simulation experiment is how to calculate the equivalent LET (Linear Energy Transfer) for laser pulse. In this paper, the calculation method considering the influences of nonlinear absorption in semiconductor, reflection and refraction on device surface and other factors is presented. Simultaneously an instance of calculation is provided, with the result in good agreement with the SEU (Single Event Upset) threshold measured by heavy ions.     

重离子在14-nm FinFET SRAM器件引起的单粒子翻转

通过重离子实验研究了14-nm FinFET工艺静态随机存取存储器(SRAM)的单粒子翻转(SEU)特性。通过使用Weibull函数拟合SEU截面获得该器件的线性能量转移(LET)阈值:0.1 MeV/(mg/cm2)。对多位翻转(MBU)贡献的统计结果表明,当LET等于40.3 MeV/(mg/cm2)时,MBU的占比超过95%。此外,FinFET SRAM的SEU截面呈现出与Fin相关的入射角度的各向异性。该研究对基于FinFET工艺的抗辐射CMOS集成电路(IC)的设计具有一定的指导作用。     

重离子核反应对单粒子翻转的影响（英文）

LET作为一个传统的工程参量,并不能完全满足单粒子翻转数据表征的需要,而且也不能直接地反映核反应的一些特性(包括核反应概率与次级粒子),因此研究了重离子与器件作用过程中核反应对单粒子翻转的影响。基于蒙特卡罗模拟与深入的分析,本研究对比了在直接电离与考虑核反应两种模式下的模拟结果。在模拟中,利用不同的重离子表征了核反应在单粒子翻转发生中所起的作用。结果显示,核反应对单粒子翻转截面的贡献依赖于离子的能量,并呈现非单调的变化关系。基于模拟的结果,建议用重离子核反应引起单粒子翻转的最恶劣情况来预估空间单粒子翻转率。     

重离子产生δ电子对SRAM单粒子翻转的影响

随着微电子器件集成度增加,由入射离子在器件灵敏区内引起的δ电子分布对器件单粒子效应的影响越来越显著;尤其是它极易引发多位翻转,严重影响设计加固的有效性。首先利用蒙特卡罗软件包Geant4模拟得到重离子在器件灵敏区内产生的δ电子分布,分析得出以下规律:入射离子单核能越高,其产生δ电子分布的径向范围越大;单核能相同的不同种离子,原子序数越大其产生的δ电子密度越大。其次,通过模拟一款45 nm静态随机存储器的单粒子翻转效应,说明δ电子和灵敏区分布共同影响器件的多位翻转。当器件灵敏区间距一定时,多位翻转率随入射离子能量的升高先上升后下降;在多位翻转率峰值和布喇格峰之间,多位翻转率随入射离子线性能量传输(LET)值的升高而降低,在该区域两侧多位翻转率随离子LET值的升高而升高。     

重离子微束单粒子翻转与单粒子烧毁效应数值模拟

用束径0.4μm的微束重离子数值模拟了单粒子翻转SEU和单粒子烧毁效应SEB.单粒子翻转给出了不同离子注入后漏区的电压(电流)随时间变化规律;计算了CMOSSRAM电路的单粒子翻转;给出了收集电荷随LET值的变化曲线并给出了某一结构器件的临界电荷;VDMOS器件单粒子烧毁给出了不同时刻沿离子径迹场强、电位线、电流和碰撞离化率的变化.     

Investigation of flux dependent sensitivity on single event effect in memory devices

Heavy-ion flux is an important experimental parameter in the ground based single event tests. The flux impact on a single event effect in different memory devices is analyzed by using GEANT4 and TCAD simulation methods. The transient radial track profile depends not only on the linear energy transfer(LET) of the incident ion, but also on the mass and energy of the ion. For the ions with the energies at the Bragg peaks, the radial charge distribution is wider when the ion LET is larger. The results extracted from the GEANT4 and TCAD simulations, together with detailed analysis of the device structure, are presented to demonstrate phenomena observed in the flux related experiment. The analysis shows that the flux effect conclusions drawn from the experiment are intrinsically connected and all indicate the mechanism that the flux effect stems from multiple ion-induced pulses functioning together and relies exquisitely on the specific response of the device.     

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。     

Impact of energy straggle on proton-induced single event upset test in a 65-nm SRAM cell

This paper presents a simulation study of the impact of energy straggle on a proton-induced single event upset(SEU)test in a commercial 65-nm static random access memory cell. The simulation results indicate that the SEU cross sections for low energy protons are significantly underestimated due to the use of degraders in the SEU test. In contrast, using degraders in a high energy proton test may cause the overestimation of the SEU cross sections. The results are confirmed by the experimental data and the impact of energy straggle on the SEU cross section needs to be taken into account when conducting a proton-induced SEU test in a nanodevice using degraders.     

Discussion of the metric in characterizing the single-event effect induced by heavy ions

The single-event effect(SEE) is the most serious problem in space environment.The modern semiconductor technology is concerned with the feasibility of the linear energy transfer(LET) as metric in characterizing SEE induced by heavy ions.In this paper,we calibrate the detailed static random access memory(SRAM) cell structure model of an advanced field programmable gate array(FPGA) device using the computer-aided design tool,and calculate the heavy ion energy loss in multi-layer metal utilizing Geant4.Based on the heavy ion accelerator experiment and numerical simulation,it is proved that the metric of LET at the device surface,ignoring the top metal material in the advanced semiconductor device,would underestimate the SEE.In the SEE evaluation in space radiation environment the top-layers on the semiconductor device must be taken into consideration.     

14 nm FinFET和65 nm平面工艺静态随机存取存储器中子单粒子翻转对比

使用中国散裂中子源提供的宽能谱中子束流,开展14 nm FinFET工艺和65 nm平面工艺静态随机存取存储器中子单粒子翻转对比研究,发现相比于65 nm器件,14 nm FinFET器件的大气中子单粒子翻转截面下降至约1/40,而多位翻转比例从2.2%增大至7.6%,源于14 nm FinFET器件灵敏区尺寸(80 nm×30 nm×45 nm)、间距和临界电荷(0.05 fC)的减小.不同于65 nm器件对热中子免疫的现象,14 nm FinFET器件中M0附近10B元素的使用导致其表现出一定的热中子敏感性.进一步的中子输运仿真结果表明,高能中子在器件灵敏区中产生的大量的射程长、LET值大的高Z二次粒子是多位翻转的产生诱因,而单粒子翻转主要来自于p,He,Si等轻离子的贡献.     

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.     

The impact of scaling on single event upset in 6T and 12T SRAMs from 130 to 22 nm CMOS technology

ABSTRACT

As transistor sizes scale down to nanometres dimensions, CMOS circuits become more sensitive to radiation. High-performance static random access memory (SRAM) cells are prone to radiation-induced single event upsets (SEU) which come from the natural space environment. The SEU generates a soft error in the transistor due to the strike of an ionizing particle. Thus, this paper compares the endurance of 12T SRAM and 6T SRAM circuit on 130 up to 22?nm CMOS technology towards SEU. Besides that, this paper discusses the trend of critical linear energy transfer (LET) and collected charge due to technology scaling for the respective circuit. The critical LET (LETcrit) and critical charge (Qcrit) of 6T are approximately 50% lower compared with 12T SRAMs.     

Discussion of the metric in characterizing single-event effect induced by heavy ions

Single-event effect (SEE) is the most serious problem in space environment. The modern semiconductor technology worries about the feasibility of the linear energy transfer (LET) as metric in characterizing SEE induced by heavy ions. In the paper, we calibrate the detailed static random access memory (SRAM) cell structure model of advanced field programmable gate array (FPGA) device using the computer-aided design tool, and calculate the heavy ion energy loss in multi-layer metal utilizing Geant4. Based on the heavy ion accelerator experiment and numerical simulation, it is proved that the metric of LET at the device surface, with ignoring the top metal material in advanced semiconductor device, would underestimate the SEE. In the SEE evaluation in space radiation environment the top-layers on the semiconductor device must be taken into consideration.     

基于蒙特卡洛和器件仿真的单粒子翻转计算方法

文章提出了一种基于蒙特卡洛和器件仿真的存储器单粒子翻转截面获取方法,可以准确计算存储器单粒子效应,并定位单粒子翻转的灵敏区域.基于该方法,计算了国产静态存储器和现场可编程门阵列(FPGA)存储区的单粒子效应的截面数据,仿真结果和重离子单粒子效应试验结果符合较好.仿真计算揭示了器件单粒子翻转敏感程度与器件n,p截止管区域面积相关的物理机理,并获得了不同线性能量转移(LET)值下单粒子翻转灵敏区域分布.采用蒙特卡洛方法计算了具有相同LET、不同能量的离子径迹分布,结果显示高能离子的电离径迹半径远大于低能离子,而低能离子径迹中心的能量密度却要高约两到三个数量级.随着器件特征尺寸的减小,这种差别的影响将会越来越明显,阈值LET和饱和截面将不能完全描述器件单粒子效应结果.     

252Cf源和重离子加速器对FPGA的单粒子效应

 对10万门基于静态随机存储器的现场可编程门阵列（FPGA）分别在锎-252（²⁵²Cf）源和HI-13串列加速器下进行了单粒子效应试验研究,测试了静态单粒子翻转截面及发生单粒子闩锁的线性能量转移阈值,并对试验结果进行了等效性分析比较。试验结果表明²⁵²Cf源引起的FPGA单粒子翻转截面比重离子加速器引起的约低1个数量级;使用²⁵²Cf源未能观测到该器件的单粒子闩锁现象,而使用重离子加速器可以测出该FPGA发生单粒子闩锁的线性能量转移阈值;在现代集成电路的宇航辐射效应地面模拟单粒子效应试验中²⁵²Cf源不是理想的测试单粒子闩锁的辐射源。     

Lifetime-enhanced transport in silicon due to spin and valley blockade

We report the observation of lifetime-enhanced transport (LET) based on perpendicular valleys in silicon by transport spectroscopy measurements of a two-electron system in a silicon transistor. The LET is manifested as a peculiar current step in the stability diagram due to a forbidden transition between an excited state and any of the lower energy states due to perpendicular valley (and spin) configurations, offering an additional current path. By employing a detailed temperature dependence study in combination with a rate equation model, we estimate the lifetime of this particular state to exceed 48 ns. The two-electron spin-valley configurations of all relevant confined quantum states in our device were obtained by a large-scale atomistic tight-binding simulation. The LET acts as a signature of the complicated valley physics in silicon: a feature that becomes increasingly important in silicon quantum devices.     

Simulation of the characteristics of low-energy proton induced single event upset

Monte Carlo simulation results are reported on the single event upset (SEU) triggered by the direct ionization effect of low-energy proton. The SEU cross-sections on the 45 nm static random access memory (SRAM) were compared with previous research work, which not only validated the simulation approach used herein, but also exposed the existence of saturated cross-section and the multiple bit upsets (MBUs) when the incident energy was less than 1 MeV. Additionally, it was observed that the saturated cross-section and MBUs are involved with energy loss and critical charge. The amount of deposited charge and the distribution with respect to the critical charge as the supplemental evidence are discussed.     

中子引起单粒子翻转过程的Monte Carlo计算模拟

从中子与硅原子相互作用的物理机理出发,利用Monte Carlo方法编制了中子引起单粒子翻转的计算模拟程序,并对14 MeV中子环境下的16K位静态存储器硅片翻转过程中的物理量进行了计算,同时可为中子引起的单粒子翻转的研究提供截面和描述内部物理过程的参考数据。     

Geant4 simulation of proton-induced single event upset in three-dimensional die-stacked SRAM device

Geant4 Monte Carlo simulation results of the single event upset(SEU) induced by protons with energy ranging from0.3 MeV to 1 GeV are reported.The SEU cross section for planar and three-dimensional(3 D) die-stacked SRAM are calculated.The results show that the SEU cross sections of the planar device and the 3 D device are different from each other under low energy proton direct ionization mechanism,but almost the same for the high energy proton.Besides,the multi-bit upset(MBU) ratio and pattern are presented and analyzed.The results indicate that the MBU ratio of the 3 D die-stacked device is higher than that of the planar device,and the MBU patterns are more complicated.Finally,the onorbit upset rate for the 3 D die-stacked device and the planar device are calculated by SPACE RADIATION software.The calculation results indicate that no matter what the orbital parameters and shielding conditions are,the on-orbit upset rate of planar device is higher than that of 3 D die-stacked device.