用SOI技术提高CMOS SRAM的抗单粒子翻转能力

提高静态随机存储器（SRAM）的抗单粒子能力是当前电子元器件抗辐射加固领域的研究重点之一。体硅CMOS SRAM不作电路设计加固则难以达到较好抗单粒子能力,作电路设计加固则要在芯片面积和功耗方面做出很大牺牲。为了研究绝缘体上硅（SOI）基SRAM芯片的抗单粒子翻转能力,突破了SOI CMOS加固工艺和128kb SRAM电路设计等关键技术,研制成功国产128kb SOI SRAM芯片。对电路样品的抗单粒子摸底实验表明,其抗单粒子翻转线性传输能量阈值大于61．8MeV／（mg／cm^2）,优于未做加固设计的体硅CMOS SRAM。结论表明,基于SOI技术,仅需进行器件结构和存储单元的适当考虑,即可达到较好的抗单粒子翻转能力。     

PDSOI SRAM单元的单粒子加固方法

通过MEDICI的二维器件模拟,提出不仅在正栅下的体区受到单粒子入射后释放电荷外,漏极也可以在受到单粒子入射后释放干扰电荷.对SOI SRAM单元中器件的漏极掺杂浓度进行优化,可以减小漏极受到单粒子入射所释放的电荷.改进了SOI SRAM的单元结构,可以提高SRAM抗单粒子翻转(SEU)的能力.     

一个实用的部分耗尽SOI器件体接触仿真模型

文章描述了PD SOI器件的体接触失效过程,介绍了一种PD SOI器件一级近似体接触电阻计算方法;提出了一种实用的体接触电阻及其版图寄生参数的模型化方法.最后,应用体接触模型,设计了一个应用于0.8 μm PD SOI 128k SRAM的灵敏放大器,给出了仿真结果.     

温度对SRAM器件单粒子翻转重离子测试的影响

本文基于单粒子效应地面重离子模拟实验,选取体硅SRAM与SOI SRAM两种待测器件,在兰州重离子加速器上（HIRLF）研究了温度对单粒子翻转测试的影响。用12C粒子对体硅SRAM器件的温度实验显示,单粒子翻转截面易受温度的影响。对于SOI SRAM器件,12C粒子测得的单粒子翻转截面随温度升高有显著的增大,但209Bi 粒子测得的单粒子翻转截面却随温度保持恒定。用Monte Carlo的方法分析了温度对单粒子翻转测试的影响规律,发现在单粒子翻转阈值LET附近温度对单粒子翻转截面有大的影响,但是随着单粒子翻转的发生接近于饱和,单粒子翻转截面渐渐的表现出低的温度依赖性。基于该模拟结果,我们对实验数据进行了分析,同时提出了一种准确评估在轨翻转率的合理方法。     

Novel SEU hardened PD SOI SRAM cell

A novel SEU hardened 10T PD SOI SRAM cell is proposed.By dividing each pull-up and pull-down transistor in the cross-coupled inverters into two cascaded transistors,this cell suppresses the parasitic BJT and source-drain penetration charge collection effect in PD SOI transistor which causes the SEU in PD SOI SRAM. Mixed-mode simulation shows that this novel cell completely solves the SEU,where the ion affects the single transistor.Through analysis of the upset mechanism of this novel cell,SEU performance is roughly equal to the multiple-cell upset performance of a normal 6T SOI SRAM and it is thought that the SEU performance is 17 times greater than traditional 6T SRAM in 45nm PD SOI technology node based on the tested data of the references.To achieve this,the new cell adds four transistors and has a 43.4%area overhead and performance penalty.     

一种新型的SOI灵敏放大器

本文利用"灵巧的体接触(Smart-Body-Contact)"技术设计出一种新型的SOI灵敏放大器.采用Hspice软件对体硅的和新型的交叉耦合灵敏放大器进行模拟和比较,发现新型的交叉耦合灵敏放大器比体硅的交叉耦合灵敏放大器延迟时间缩短30%,最小电压分辨可达0.05V.最后,我们成功地将该电路应用于CMOS/SOI 64Kb SRAM电路,电路存取时间仅40ns.     

IBM制成32nm SOI嵌入式DRAM

IBM宣布已制成32nm SOI嵌入式DRAM测试芯片，并称该芯片是半导体业界面积最小、密度最高、速度最快的片上动态存储器。IBM表示，使用SOI技术可使芯片性能提高30％，功耗降低40％，和32nm、22nm的片上SRAM相比，具有更理想的密度和速度。     

PDSOI CMOS SRAM单元临界电荷的确定

PDSOI CMOS SRAM单元的临界电荷(Critical Charge)是判断SRAM单元发生单粒子翻转效应的依据.利用针对1.2μm抗辐照工艺提取的PDSOI MOSFET模型参数,通过HSPICE对SRAM 6T存储单元的临界电荷进行了模拟,指出了电源电压及SOI MOEFET寄生三极管静态增益β对存储单元临界电荷的影响,并提出了在对PDSOI CMOS SRAM进行单粒子辐照实验中,电源电压的最恶劣偏置状态应为电路的最高工作电压.     

驱动能力对SOI SRAM单元单粒子效应的影响仿真

采用silvaco软件对抗辐射不同沟道宽度的PD SOI NMOS器件单元进行了三维SEU仿真,将瞬态电流代入电路模拟软件HSPICE中进行SRAM存储单元单粒子翻转效应的电路模拟。通过这种电路模拟的方法,可以得到SRAM存储单元的LET阈值。通过对比LET阈值的实际测量值,验证了这种方法的实用性,并对不同驱动能力的SRAM单元进行了翻转效应的对比。在NMOS和PMOS驱动比相同的情况下,沟道宽度越大,SRAM的翻转LET阈值反而越高。     

SOI反偏肖特基势垒动态阈值MOS特性

将Ti硅化物-p型体区形成的反偏肖特基势垒结构引入绝缘体上硅动态阈值晶体管.传统栅体直接连接DTMOS,为了避免体源二极管的正向开启,工作电压应当低于0.7V.而采用反偏肖特基势垒结构,DTMOS的工作电压可以拓展到0.7V以上.实验结果显示,室温下采用反偏肖特基势垒SOI DTMOS结构,阈值电压可以动态减小200mV.反偏肖特基势垒SOI DTMOS结构相比于传统模式,显示出优秀的亚阈值特性和电流驱动能力.另外,对浮体SOI器件、传统模式SOI器件和反偏肖特基势垒SOI DTMOS的关态击穿特性进行了比较.     

Device Design and Optimization Methodology for Leakage and Variability Reduction in Sub-45-nm FD/SOI SRAM

Ultrathin-body fully depleted silicon-on-insulator (UTB FD/SOI) devices have emerged as a possible candidate in sub-45-nm technologies and beyond. This paper analyzes leakage and stability of FD/SOI 6T SRAM cell and presents a device design and optimization strategy for low-power and stable SRAM applications. We show that large variability and asymmetry in threshold-voltage distribution due to random dopant fluctuation (RDF) significantly increase leakage spread and degrade stability of FD/SOI SRAM cell. We propose to optimize FD devices using thinner buried oxide (BOX) structure and lower body doping combined with negative back-bias or workfunction engineering in reducing the RDF effect. Our analysis shows that thinner BOX and cooptimization of body doping and back biasing are efficient in designing low-power and stable FD/SOI SRAM cell in sub-45-nm nodes.     

抗辐射128kb PDSOI静态随机存储器

介绍在部分耗尽绝缘体上硅(PD SOI)衬底上形成的抗辐射128kb静态随机存储器.在设计过程中,利用SOI器件所具有的特性,对电路进行精心的设计和层次化版图绘制,通过对关键路径和版图后全芯片的仿真,使得芯片一次流片成功.基于部分耗尽SOI材料本身所具有的抗辐射特性,通过采用存储单元完全体接触技术和H型栅晶体管技术,不仅降低了芯片的功耗,而且提高了芯片的总体抗辐射水平.经过测试,芯片的动态工作电流典型值为20mA@10MHz,抗总剂量率水平达到500krad(Si),瞬态剂量率水平超过2.45×1011 rad(Si)/s.这些设计实践必将进一步推动PD SOI CMOS工艺的研发,并为更大规模抗辐射电路的加固设计提供更多经验.     

抗辐射128kb PDSOI静态随机存储器

介绍在部分耗尽绝缘体上硅(PD SOI)衬底上形成的抗辐射128kb静态随机存储器.在设计过程中,利用SOI器件所具有的特性,对电路进行精心的设计和层次化版图绘制,通过对关键路径和版图后全芯片的仿真,使得芯片一次流片成功.基于部分耗尽SOI材料本身所具有的抗辐射特性,通过采用存储单元完全体接触技术和H型栅晶体管技术,不仅降低了芯片的功耗,而且提高了芯片的总体抗辐射水平.经过测试,芯片的动态工作电流典型值为20mA@10MHz,抗总剂量率水平达到500krad(Si),瞬态剂量率水平超过2.45×1011 rad(Si)/s.这些设计实践必将进一步推动PD SOI CMOS工艺的研发,并为更大规模抗辐射电路的加固设计提供更多经验.     

A 15 nm Ultra‐thin Body SOI CMOS Device' with Double Raised Source/Drain for 90 nm Analog Applications

Fully‐depleted silicon‐on‐insulator (FD‐SOI) devices with a 15 nm SOI layer thickness and 60 nm gate lengths for analog applications have been investigated. The Si selective epitaxial growth (SEG) process was well optimized. Both the singleraised (SR) and double‐raised (DR) source/drain (S/D) processes have been studied to reduce parasitic series resistance and improve device performance. For the DR S/D process, the saturation currents of both NMOS and PMOS are improved by 8 and 18%, respectively, compared with the SR S/D process. The self‐heating effect is evaluated for both body contact and body floating SOI devices. The body contact transistor shows a reduced self‐heating ratio, compared with the body floating transistor. The static noise margin of an SOI device with a 1.1 µm² 6T‐SRAM cell is 190 mV, and the ring oscillator speed is improved by 25 % compared with bulk devices. The DR S/D process shows a higher open loop voltage gain than the SR S/D process. A 15 nm ultra‐thin body (UTB) SOI device with a DR S/D process shows the same level of noise characteristics at both the body contact and body floating transistors. Also, we observed that noise characteristics of a 15 nm UTB SOI device are comparable to those of bulk Si devices.     

Measurement of transient effects in SOI DRAM/SRAM accesstransistors

Bitline-induced transient effects in access transistors pose a problem in SOI DRAM and SRAM cells. The floating-body potential is affected by the bitline so changes in the bitline potential may upset the charge stored in the memory cell. Transient effects in SOI access transistors are measured versus the time the bitline is at high voltage, and V_DD for fully- and partially-depleted SOI devices. Bulk devices show no bitline-induced transient effects. Measurements show that the magnitude of the charge upset can be large enough to disturb the charge stored in DRAM and SRAM cells. Measurements also show that for any substantial upsets to occur, the time the bitline has to be at high voltage is on the order of milliseconds. Although the effect of bitline transitions is cumulative, the amount of charge upset when the bitline switches rapidly (i.e., millisecond periods) is shown to be negligible. Thus, proper design of SRAM upset-charge protection and DRAM refresh time should circumvent this problem     

体Si和SOI工艺SRAM芯片电磁敏感度的温度效应

考虑到芯片实际应用环境的复杂性,针对体硅(silicon,Si)和绝缘体上硅(silicon on insulator,SOI)两种工艺的静态随机存储器(static random-access memory,SRAM),测试研究温度效应分别对这两种不同工艺存储器芯片敏感度的影响.依据两种工艺下金属氧化物半导体(met...     

部分耗尽SOI工艺器件辐射效应的研究

对0.13μm部分耗尽SOI工艺的抗辐射特性进行了研究.首先通过三维仿真研究了单粒子事件中的器件敏感区域,随后通过实验分析了器件的总剂量效应.三维仿真研究了离子入射位置不同时SOI NMOS器件的寄生双极效应和电荷收集现象,结果表明,离子入射在晶体管的体区和漏区时,均可以引起较大水平的电荷收集.对SRAM单元的单粒子翻转效应(SEU)进行了仿真,结果表明,体区和反偏的漏区都是翻转的敏感区域.通过辐照实验分析了器件的总剂量效应,在该工艺下对于隐埋氧化层,关断状态是比传输门状态更劣的辐射偏置条件.     

Bulk-layout-compatible 0.18-μm SOI-CMOS technology usingbody-tied partial-trench-isolation (PTI)

Partial-trench-isolated (PTI) 0.18-μm SOI-CMOS technology has been established to realize the body-tied structure and eliminate floating-body effects. The body potential of PTI SOI MOSFETs is fixed through the silicon layer under the PTI oxide. It was revealed that the body-tied PTI structure provides immunity from kink effects and improves drive current as compared with floating transistors. The SOI inherent merits were investigated by delay-time measurement. Low junction capacitance, coupling effects and low back-gate-bias effects of PTI CMOS offer excellent speed performance. Stable function and body-coupling benefits are obtained with proper body engineering. The full-bit functions of a 4-Mbit SRAM were obtained with a reasonable yield. The yield of the SOI SRAM is almost the same as that of the bulk SRAM. An abnormal leakage current was not observed up to a supply voltage of 2.6 V corresponding to the stress voltage of the burn-in process. It was demonstrated that PTI technology possesses layout and process compatibility with bulk. It is concluded that the PTI technology can expand SOI applications in system-level large-scale integrations (LSIs) by cutting off the floating-SOI constraint     

Performance advantages of 3-D digital integrated circuits in a mixed SOI and bulk CMOS design space

Three-dimensional (3-D) integrated circuits (ICs), with multiple stacked device layers, offer a unique design opportunity to use both bulk and partially depleted (PD) silicon-on-insulator (SOI) CMOS devices in a single circuit design. Such 3-D designs can, for example, minimize the body effect common in bulk designs and reduce adverse floating-body effects (FBE) common in PD SOI designs. Sequential 3-D technology such as exfoliation-based single-crystal silicon layer transfer allows a low-temperature approach to 3-D integration with high-density interconnectivity. Using the characteristics of this technology, we present the mixed SOI bulk (MSB) design approach that effectively re-maps conventional VLSI designs to the 3-D design space. Tradeoffs in delay, noise margin, power, and circuit footprint are analyzed and demonstrated through analyzes of static, dynamic, pass-transistor, and SRAM circuits.     

A room temperature 0.1 μm CMOS on SOI

An advanced 0.1 μm CMOS technology on SOI is presented. In order to minimize short channel effects, relatively thick nondepleted (0.15 μm) SOI film, highly nonuniform channel doping and source-drain extension-halo were used. Excellent short channel effects (SCE) down to channel lengths below 0.1 μm were obtained. It is shown that undepleted SOI results in better short channel effect when compared to ultrathin depleted SOI. Devices with little short channel effect all the way to below 500 Å effective channel length were obtained. Furthermore, utilization of source-drain extension-halo minimizes the bipolar effect inherent in the floating body. These devices were applied to a variety of circuits: Very high speeds were obtained: Unloaded delay was 20 ps, unloaded NAND (FI=FO=3) was 64 ps, and loaded NAND (FI=FO=3, C_L=0.3 pF) delay was 130 ps at supply of 1.8 V. This technology was applied to a self-resetting 512 K SRAM. Access times of 2.5 ns at 1.5 V and 3.5 ns at 1.0 V were obtained