Coupling induced soft error mechanisms in nanoscale CMOS technologies

Due to scaling induced effects, CMOS circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. Researchers mostly considered SE transients as the main cause for combinational logic (CL) related radiation-induced soft errors. However, for high-reliability applications such as avionics, military and medical applications, additional sources such as SE induced soft delays, clock jitters, false clock pulses and crosstalk effects need to be included in soft-error reliability analysis. As technologies advance, coupling effects among interconnects increasingly cause SE transients to contaminate electronically unrelated circuit paths, which can in turn increase the “SE susceptibility” of CMOS circuits. This work focuses on such coupling induced soft error mechanisms in CL, namely the SE crosstalk noise and delay effects. An attempt has been made to compare SE crosstalk noise and SE transient effects, and crosstalk contribution to soft error rate has been examined. In addition, the SE induced coupling delay effect has been studied and compared to radiation induced soft delay effect for various technologies. Results show that, in newer technologies, the SE coupling delay becomes quite comparable to soft delay effect, although caused indirectly by cross-coupling effects. In comparisons, the distributed nature of interconnects has been taken into account and results are demonstrated using HSPICE simulations with interconnect and device parameters derived in 130, 90 and 65 nm technologies.     

Modeling single event crosstalk speedup in nanometer technologies

With advances in CMOS technology, circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. In addition, coupling effects among interconnects can cause SE transients to spread electronically unrelated circuit paths which may increase the SE Susceptibility of CMOS circuits. The coupling effects among interconnects need to be considered in single event modeling and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. This work reports on the signal speedup effects caused by SE crosstalk and then proposes a best-case delay estimation methodology for use in design automation tools for the first time to our knowledge. The SE coupling speedup expressions derived show very good results in comparison to HSPICE results. Results show an average error of about 8.42% for best-case delay while allowing for very fast analysis in comparison to HSPICE.     

Reliability evaluation for single event crosstalk via probabilistic transfer matrix

To quantitatively analyze the influence on integrated circuits (ICs) by crosstalk and single event effects, the reliability of ICs under these effects was evaluated via probabilistic transfer matrix (PTM). The basic theory of PTM was briefly introduced. By modifying the right probability of gates in PTM, the influence from single event effect on the reliability was obtained. By considering the error probability of signal transportation through interconnects, the reliability under crosstalk was calculated. The results show that crosstalk and single event effects will both decrease the reliability of ICs. The farther from the output the gate is suffered from single event effect, the less significant influences on the reliability decreased. The crosstalk effects will bring worse influences on the reliability than single event effects. The technologies for improving reliability of ICs should take more attentions to the crosstalk effects and multi-single event effects.     

Effect of coupling parasitics and CMOS driver width on transition time for dynamic inputs

This article analyses the effect of coupling parasitics and CMOS gate driver width on transition time delay of coupled interconnects driven by dynamically switching inputs. Propagation delay through an interconnect is dependent not only on the technology/topology but also on many other factors such as input transition time, load characteristic, driving gate dimensions and so on. The delay is affected by rise/fall time of the signal, which in turn is dependent on the driving gate and the load presented to it. The signal transition time is also a strong function of wire parasitics. This article addresses the different issues of signal transition time. The impact of inter-wire parasitics and driver width on signal transition time are presented in this article. Furthermore, the effect of unequal transition time of the inputs to interconnect lines on crosstalk noise and delay is analysed. To demonstrate these effects, two distributed RLC lines coupled capacitively and inductively are taken into consideration. The simulations are run at three different technology nodes, viz. 65 nm, 90 nm and 130 nm.     

纳米级CMOS集成电路的单粒子效应及其加固技术

空间应用的集成电路受到辐射效应的影响,会出现瞬态干扰、数据翻转、性能退化、功能失效甚至彻底毁坏等问题.随着器件特征尺寸进入到100nm以下（以下简称纳米级）,这些问题的多样性和复杂性进一步增加,单粒子效应成为集成电路在空间可靠性应用的主要问题,给集成电路的辐射效应评估和抗辐射加固带来了诸多挑战.本文以纳米级CMOS集成电路为研究对象,结合近年来国内外的主要技术进展,介绍研究团队在65nm集成电路单粒子效应和加固技术方面的研究成果,包括首次提出的单粒子时域测试和分析方法、单粒子多节点翻转加固方法和单粒子瞬态加固方法等.     

SET and noise fault tolerant circuit design techniques: Application to 7 nm FinFET

In the near future of high component density and low-power technologies, soft errors occurring not only in memory systems and latches but also in the combinational parts of logic circuits will seriously affect the reliable operation of integrated circuits. This paper presents a novel design style which reduces the impact of radiation-induced single event transients (SET) on logic circuits, and enhances the robustness in noisy environments. The independent design style of this method achieves SET mitigation and noise immunity by strengthening the sensitive nodes using a technique similar to feedback. A realization for this methodology is presented in 7 nm FinFET and in order to check the accuracy of our proposal, we compare it with others techniques for hardening radiation at the transistor level against a single event transient. Simulation results show that the proposed method has a good soft error tolerance capability as well as better noise immunity.     

Single Event crosstalk shielding for CMOS logic

With advances in technology scaling, CMOS circuits are increasingly more sensitive to transient pulses caused by Single Event particles. Hardening techniques for CMOS combinational logic have been developed to address the problems associated with Single Event transients, but in these designs, Single Event crosstalk effects have been ignored. In order to complement the Single Event upset (SEU) hardening process, coupling effects among interconnects need to be considered in the Single Event hardening and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. As technologies advance, the coupling effects increasingly cause SE transients to contaminate electronically unrelated circuit paths which can in turn increase the “Single Event susceptibility” of CMOS circuits. Serious effects may occur if the affected line is a clock line or an input line of voters in triple-modular redundancy (TMR) circuit. Hence, this work first analyzes Single Event crosstalk on recent technologies and then proposes hardening techniques to reduce Single Event crosstalk. Hardening results are demonstrated using HSpice Simulations with interconnect and device parameters derived in 90 nm technology.     

Single event crosstalk prediction in nanometer technologies

As CMOS technology continues to scale down, circuits become increasingly more sensitive to transient pulses caused by single event (SE) particles. On the other hand, coupling effects among interconnects can cause single event transients to contaminate electronically unrelated circuit paths which may increase the SE susceptibility of CMOS circuits. The coupling effects among interconnects need to be considered in single event hardening, modeling and analysis of CMOS logic gates due to technology scaling effects that increase both SE vulnerability and crosstalk effects. This work, for the first time, proposes an SE crosstalk noise estimation method for use in design automation tools. The proposed method uses an accurate 4-π model for interconnect and correctly models the effect of non-switching aggressors as well as aggressor tree branches noting the resistive shielding effect. The SE crosstalk noise expressions derived show very good results in comparison to HSPICE results. Results show that average error for noise peak is about 5.2% while allowing for very fast analysis in comparison to HSPICE.     

基于65nm工艺数字IC物理设计中信号串扰的预防

数字集成电路的不断发展和制造工艺的不断进步,使得物理设计面临着越来越多的挑战.特征尺寸的减小,使得后端设计过程中解决信号完整性问题是越来越重要.互连线间的串扰就是其中的一个,所以在后端设计的流程中,对串扰的预防作用也显得尤为重要.本文就TSMC 65nm工艺下,根据具体的设计模块,探索物理设计流程中如何才能更好的预防串扰对芯片时序的影响.     

Soft Error Rate Reduction Using Circuit Optimization and Transient Filter Insertion

This paper describes a tunable transient filter (TTF) design for soft error rate reduction in combinational logic circuits. TTFs can be inserted into combinational circuits to suppress propagated single-event transients (SETs) before they can be captured in latches or flip-flops. TTFs are tuned by adjusting the maximum width of the propagated SET that can be suppressed. A TTF requires 6–14 transistors, making it an attractive cost-effective option to reduce the soft error rate in combinational circuits. A global optimization approach based on geometric programming that integrates TTF insertion with dual-V _DD and gate sizing is described. Simulation results for the 65 nm process technology indicate that a 17–48× reduction in the soft error rate can be achieved with this approach.     

Low cost and highly reliable radiation hardened latch design in 65 nm CMOS technology

As a consequence of technology scaling down, gate capacitances and stored charge in sensitive nodes are decreasing rapidly, which makes CMOS circuits more vulnerable to radiation induced soft errors. In this paper, a low cost and highly reliable radiation hardened latch is proposed using 65 nm CMOS commercial technology. The proposed latch can fully tolerate the single event upset (SEU) when particles strike on any one of its single node. Furthermore, it can efficiently mask the input single event transient (SET). A set of HSPICE post-layout simulations are done to evaluate the proposed latch circuit and previous latch circuits designed in the literatures, and the comparison results among the latches of type 4 show that the proposed latch reduces at least 39% power consumption and 67.6% power delay product. Moreover, the proposed latch has a second lowest area overhead and a comparable ability of the single event multiple upsets (SEMUs) tolerance among the latches of type 4. Finally, the impacts of process, supply voltage and temperature variations on our proposed latch and previous latches are investigated.     

High performance energy efficient radiation hardened latch for low voltage applications

Energy efficiency is considered to be the most critical design parameter for IoT and other ultra low power applications. However, energy efficient circuits show a lesser immunity against soft error, because of the smaller device node capacitances in nanoscale technologies and near-threshold voltage operation. Due to these reasons, the tolerance of the sequential circuits to SEUs is an important consideration in nanoscale near threshold CMOS design. This paper presents an energy efficient SEU tolerant latch. The proposed latch improves the SEU tolerance by using a clocked Muller- C and memory elements based restorer circuit. The parasitic extracted simulations using STMicroelectronics 65 nm CMOS technology show that by employing the proposed latch, an average improvement of ∼40% in energy delay product (EDP), is obtained over the recently reported latch. Moreover, the proposed latch is also validated in a TCAD calibrated PTM 32 nm framework and PTM 22 nm CMOS technology nodes. In 32 nm and 22 nm technologies, the proposed latch improves the EDP ∼12% and 59% over existing latches respectively.     

Mixed logic style adder circuit designed and fabricated using SOI substrate for irradiation-hardened experiment

This paper proposed a rail to rail swing, mixed logic style 28-transistor 1-bit full adder circuit which is designed and fabricated using silicon-on-insulator (SOI) substrate with 90 nm gate length technology. The main goal of our design is space application where circuits may be damaged by outer space radiation; so the irradiation-hardened technique such as SOI structure should be used. The circuit’s delay, power and power–delay product (PDP) of our proposed gate diffusion input (GDI)-based adder are HSPICE simulated and compared with other reported high-performance 1-bit adder. The GDI-based 1-bit adder has 21.61% improvement in delay and 18.85% improvement in PDP, over the reported 1-bit adder. However, its power dissipation is larger than that reported with 3.56% increased but is still comparable. The worst case performance of proposed 1-bit adder circuit is also seen to be less sensitive to variations in power supply voltage (VDD) and capacitance load (CL), over a wide range from 0.6 to 1.8 V and 0 to 200 fF, respectively. The proposed and reported 1-bit full adders are all layout designed and wafer fabricated with other circuits/systems together on one chip. The chip measurement and analysis has been done at VDD = 1.2 V, CL = 20 fF, and 200 MHz maximum input signal frequency with temperature of 300 K.     

Experimental results and modeling techniques for substrate noise inmixed-signal integrated circuits

An experimental technique is described for observing the effects of switching transients in digital MOS circuits that perturb analog circuits integrated on the same die by means of coupling through the substrate. Various approaches to reducing substrate crosstalk (the use of physical separation of analog and digital circuits, guard rings, and a low-inductance substrate bias) are evaluated experimentally for a CMOS technology with a substrate comprising an epitaxial layer grown on a heavily doped bulk wafer. Observations indicate that reducing the inductance in the substrate bias is the most effective. Device simulations are used to show how crosstalk propagates via the heavily doped bulk and to predict the nature of substrate crosstalk in CMOS technologies integrated in uniform, lightly doped bulk substrates, showing that in such cases the substrate noise is highly dependent on layout geometry. A method of including substrate effects in SPICE simulations for circuits fabricated on epitaxial, heavily doped substrates is developed     

A Near-Threshold Soft Error Resilient 7T SRAM Cell with Low Read Time for 20 nm FinFET Technology

Shrinking of technology node in advanced VLSI devices and scaling of supply voltage degrade the performance characteristics and reduce the soft error resilience of modern downscaled digital circuits. In this paper, we propose a reliable near-threshold 7T SRAM cell with single ended read and differential write operations based on a previous proposed 5T cell. Our new cell improves read speed without degrading of write speed compared to the recently reported 7T cell. Furthermore, our proposed cell provides high soft error reliability amongst all the SRAM cells mentioned in this paper. We compared the performance and reliability characteristics of 5T, 6T, 8T and previous 7T cells with our new 7T SRAM cell to show its efficacy. The simulations are performed using HSPICE in 20 nm FinFET technology at V_DD = 0.5 V. The results show that the new 7T cell has high write speed, read and write margins with improved read speed and low leakage power in the hold “0” state compared to 5T cell. In addition, the study of performance parameters under process and environmental variations considering ageing effect in near-threshold region shows the robustness of the proposed 7T SRAM cell against these variations.     

互连线延时和串扰的估算方法

本文综述了集成电路中互连线的延时和串扰的估算方法，分析了各种估算方法的精度和复杂度，同时提出了今后互连线延时和串扰估算所需要解决的新问题。     

一种基于三联锁结构的单粒子翻转加固锁存器

本文提出了一种基于三联锁结构的单粒子翻转加固锁存器。该锁存器使用保护门和反相器在其内部构建三路反馈,以此获得对发生在任一电路节点上的单粒子效应的自恢复能力,有效抑制由粒子轰击半导体引发的电荷沉积带来的影响。本文在详细分析已报道的三种抗辐射锁存器结构可靠性的基础上,针对其在单粒子效应作用下,或单粒子效应和耦合串扰噪声的共同作用下依然可能发生翻转的问题,指出本文提出的锁存器可通过内部的三联锁结构对上述问题进行有效的消除。所有结论均得到电路级单粒子效应注入仿真结果,以及基于经典串扰模型模拟串扰耦合和单粒子效应共同作用的仿真结果的支持和验证。     

Layout-based Single Event Mitigation Techniques for Dynamic Logic Circuits

Due to the intrinsic lack of restoring paths, dynamic logic circuits have significant single-event susceptibility, and thus, they are not preferred in applications requiring high reliability when compared to static logic. However, in high speed applications, this circuit family is still very attractive. This papers presents two layout-based single-event resilient dynamic logic designs. The resultant SET pulse is suppressed because of charge-sharing in the layout-level. Simulation results verify that they enjoy higher single event tolerance. Experimental results validate the fact that approximately 20?~?30 % of magnitude reduction in cross-section is achieved in both designs. On the other hand, the increase in single-event performance is achieved at the expense of power and area overheads of 10 and 15 %, respectively, using our layout style in 130 nm CMOS bulk technology.     

Reliability for nanomagnetic logic (NML) readout circuit under single event effect

In the application for the space radiation environment, NML circuits face a reliability challenge mainly from their CMOS peripheral circuits, suffering from single event effects (SEE). An on-chip readout interface circuit (RIC) for NML circuit is designed based on dual-barrier magnetic tunnel junction (DB-MTJ). The sensitive nodes to SEE in RIC are analyzed. The SEU required critical charge in RIC is described. The impacts of energetic particle hitting time and technology node on the critical charge are studied. As the technology node scales down, the critical charge will significantly decrease. Two efficient hardening technologies for RIC are presented: local transistors׳ size and symmetrical load capacitances. By increasing local transistors׳ size or decreasing the load capacitance, the critical charge will be improved, which enhances the immunity to SEE.     

Bulk built in current sensors for single event transient detection in deep-submicron technologies

As device dimensions are scaled down, single event transients (SET) are increasingly affecting the reliability of integrated circuits. An SET is a transient voltage perturbation caused by an energetic particle strike at the semiconductor. This work studies the applicability of bulk built in current sensors (bulk-BICS) for SET detection in deep-submicron technologies. The bulk-BICS detects the transient current generated by the impact of an energetic particle at a sensitive circuit node. The efficiency and applicability of this approach to SET detection is demonstrated through device and circuit level simulations.