一种新式SEU加固PD SOI SRAM单元

本文提出了一种新式SEU加固的10管PD SOI静态存储单元。通过将互锁反相器中的上拉和下拉管分割成两个串联的晶体管,该单元可有效抑制PD SOI晶体管中的寄生BJT和源漏穿通电荷收集效应,这两种电荷收集效应是引起PD SOISRAM翻转的主要原因。通过混合仿真发现,与穿通的浮体6T单元相比,该单元可完全解决粒子入射单个晶体管引起的单粒子翻转。通过分析该新式单元的翻转机制,认为其SEU性能近似与6T SOI SRAM的单粒子多位翻转性能相等。根据参考文献的测试数据,粗略估计该新式单元的SEU性能比普通45nm 6T SOI SRAM单元提升了17倍。由于新增加了四个晶体管,该单元在面积上增加了43.4%的开销,性能方面有所降低。     

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.     

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.     

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.     

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。     

TCAD/Physics-Based Analysis of High-Density Dual-BOX FD/SOI SRAM Cell With Improved Stability

This paper presents a new SRAM cell using a global back-gate bias scheme in dual buried-oxide (BOX) FD/SOI CMOS technologies. The scheme uses a single global back-gate bias for all cells in the entire columns or subarray, thereby reducing the area penalty. The scheme improves 6T SRAM standby leakage, read stability, write ability, and read/write performance. The basic concept of the proposed scheme is discussed based on physical analysis/equation to facilitate device parameter optimization for SRAM cell design in back-gated FD/SOI technologies. Numerical 2-D mixed-mode device/circuit simulation results validate the merits and advantages of the proposed scheme.      

一种全nMOS SOI晶体管4管静态存储器单元

提出了一种新颖的无负载4管全部由nMOS管组成的随机静态存储器(SRAM)单元.该SRAM单元基于32nm绝缘体上硅(SOI)工艺结点,它包含有两个存取管和两个下拉管. 存取管的沟道长度小于下拉管的沟道长度. 由于小尺寸MOS管的短沟道效应,在关闭状态时存取管具有远大于下拉管的漏电流,从而使SRAM单元在保持状态下可以维持逻辑“1" . 存储节点的电压还被反馈到存取管的背栅上,使SRAM单元具有稳定的“读”操作. 背栅反馈同时增强了SRAM单元的静态噪声容限(SNM). 该单元比传统的6管SRAM单元和4管SRAM单元具有更小的面积. 对SRAM单元的读写速度和功耗做了仿真和讨论. 该SRAM单元可以工作在0.5V电源电压下.     

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     

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 SRAM灵敏放大器中动态体放电技术研究

在SOI SRAM锁存器型灵敏放大器中,设计了一对小的下拉管,用来动态地释放交叉耦合反相器中N管上的体电荷。这种动态体放电的方法有效地解决了部分耗尽SOI CMOS器件体电位不匹配的问题,得到了可重复性低阈值电压,提高了SRAM的读取速度。     

质子引入的6T SRAM单粒子翻转截面预测模型

提出了一种基于SOI工艺6T SRAM单元质子辐射的单粒子饱和翻转截面的预测模型,该模型通过器件物理来模拟辐照效应,利用版图和工艺参数来预测质子引入的单粒子饱和翻转截面。该模型采用重离子的SPICE测试程序对质子辐射的翻转截面进行预测,该方法简单高效,测试实例表明在0.15μm SOI工艺下,预测的质子引入的单粒子翻转饱和截面和实际测试的翻转截面一致。     

CMOS/SOI 64Kb静态随机存储器

对一种CMOS/SOI 64Kb静态随机存储器进行了研究,其电路采用8K×8的并行结构体系．为了提高电路的速度,采用地址转换监控(Address-Translate-Detector,ATD)、两级字线(Double-Word-Line,DWL)和新型的两级灵敏放大等技术,电路存取时间仅40ns;同时,重点研究了SOI静电泄放(Electrostatic-Discharge,ESD)保护电路和一种改进的灵敏放大器,设计出一套全新ESD电路,其抗静电能力高达4200—4500V．SOI 64Kb CMOS静态存储器采用1.2μm SOI CMOS抗辐照工艺技术,芯片尺寸为7.8mm×7.24mm．     

Implementation of the Cell Broadband Engine™ in 65 nm SOI Technology Featuring Dual Power Supply SRAM Arrays Supporting 6 GHz at 1.3 V

The 65 nm cell broadband enginetrade (cell BE) is a multi-core SoC, implemented in a high performance SOI technology featuring a separate dual power supply for SRAM arrays to improve stability and performance using an elevated voltage. A new method is shown to analyze the SRAM cell under application conditions which was used to tune the cell for stability, write-ability and performance. An improved write scheme is shown which widens the overall functional window and allows setting the power/performance point of the arrays independently of the surrounding logic. Hardware measurements demonstrate the advantages of the dual power supply under different aspects.     

An 8 Mb SRAM in 45 nm SOI Featuring a Two-Stage Sensing Scheme and Dynamic Power Management

This paper describes an 8 Mb SRAM test chip that has been designed and fabricated in a 45 nm Silicon-On-Insulator (SOI) CMOS technology. The test chip comprises of sixteen 512 kb instances and is designed for use as the principal compilable one-port embedded-SRAM block in a 45 nm ASIC library. Challenges associated with SRAM cell design in SOI are overcome and resulted in a cell size of 0.315 mum² . The paper introduces two circuit techniques that address the AC and DC power consumption issues facing today's embedded-SRAMs. The first technique addresses AC power dissipation by utilizing a two-stage, body-contacted sensing scheme that, among other improvements, achieves a 68% improvement in read power under constant voltage and frequency compared to the previous generation macro . The second technique addresses the DC power consumption by introducing a single-device, header based dynamic leakage suppression scheme that reduces total macro leakage power by 38% with no wake-up cycle requirements.     

Device and circuit level suppression techniques for random-dopant-induced static noise margin fluctuation in 16-nm-gate SRAM cell

In this study, a three-dimensional “atomistic” coupled device-circuit simulation is performed to explore the impact of process-variation-effect (PVE) and random-dopant-fluctuation (RDF) on static noise margin (SNM) of 16-nm complementary metal-oxide-semiconductor (CMOS) static random access memory (SRAM) cells. Fluctuation suppression approaches, based on circuit and device viewpoints, are further implemented to examine the associated characteristics in 16-nm-gate SRAM cells. From the circuit viewpoint, the SNM of 8T planar SRAM is enlarged to 230 mV and the variation of SNM (σ_SNM) is reduced to 22 mV at a cost of 30% extra chip area. As for device level improvement, silicon-on-insulator (SOI) FinFETs replaced the planar MOSFETs in 6T SRAM is further examined. The SNM of 6T SOI FinFETs SRAM is 125 mV and the σ_SNM is suppressed significantly to 5.4 mV. However, development of fabrication process for SOI FinFET SRAM is crucial for sub-22 nm technology era.     

一种低压低功耗SRAM/SOI单元设计

提出一种改进4管自体偏压结构SRAM/SOI单元.基于TSUPREM4和MEDICI软件的模拟和结构性能的分析,设计单元结构并选取结构参数.该结构采用nMOS栅下的含p+埋沟的衬底体电阻代替传统6管CMOSSRAM单元中的pMOS元件,具有面积小、工艺简单的优点.该结构可以在0.5V的电源电压下正常工作,与6管单元相比,该单元瞬态响应正常,功耗只有6管单元的1/10,满足低压低功耗的要求.     

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     

FDSOI and Bulk CMOS SRAM Cell Resilience to Radiation Effects

With shrinking dimensions and increased number of on-chip transistors radiation can provoke faults in integrated circuits even at sea level. This paper presents a comparison of fully depleted SOI (FDSOI) and Bulk CMOS 6T SRAM cells' resilience to radiation effects. Both cells were simulated using TCAD tools, considering heavy-ion impacts in different locations of the transistor as well as using different impact angles. Two types of radiation effects have been considered: Single-Event Transients (SETs) and Single-Event Upsets (SEUs). The minimum critical collected charge (CC) to flip a cell is almost the same in both technologies. However, it is shown that a FDSOI SRAM cell needs a heavy-ion impact with a Linear Energy Transfer (LET) around 10 times greater than a Bulk-CMOS SRAM cell, to generate a similar CC and to flip a cell.     

A Low Power SRAM/SOI Memory Cell Design

提出一种改进4管自体偏压结构SRAM/SOI单元. 基于TSUPREM4和MEDICI软件的模拟和结构性能的分析，设计单元结构并选取结构参数. 该结构采用nMOS栅下的含p+埋沟的衬底体电阻代替传统6管CMOS SRAM单元中的pMOS元件，具有面积小、工艺简单的优点. 该结构可以在0.5V的电源电压下正常工作，与6管单元相比，该单元瞬态响应正常，功耗只有6管单元的1/10，满足低压低功耗的要求.     

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...