Bottom electrode and barrier materials issues in stacked capacitor type ferroelectric memories

Abstract

A number of basic materials issues need to be solved to successfully realize the stacked ferroelectric capacitor cell concept, which is needed for FERAM with densities beyond about 1Mb. This paper discusses barrier materials selection and the role of bottom electrode microstructure for future PZT-based FERAM based on the stacked cell concept. Conventional methods for PZT texture control, employing Pt as a template layer, are less suited for stacked cell layouts, because of the poor diffusion barrier properties of Pt. Modification of the microstructure of RuO₂ bottom electrodes has allowed us to eliminate the effect of underlying layers on the texture of PZT. The advantages of this approach in view of increasing circuit density of PZT-based FERAMs are discussed.     

Imprint testing of ferroelectric capacitors used for non-volatile memories

Abstract

A set of criteria is presented, based on the polarization versus electric field hysteresis characteristics, which can be used to reveal a tendency towards imprint failure in ferroelectric capacitors. A series of pulsed voltage waveforms, generated by the RT66A ferroelectric tester, are utilized to validate our established criteria for the tendency towards imprinting. The tests have been performed on hetero-structure Pb(Zr_xTi_1?x)O₃(PZT)-based capacitors produced by a pulsed laser ablation depositon technique (PLAD). The loss of retained charge in the ferroelectric capacitors is considered in light of the imprint test methodology. Rates of retention loss and imprint are extracted from the experimental data and treated as separate processes that lead to device failure. The rate of approach towards imprint failure is found to be influenced by the magnitude of the read pulse.     

Recent progress in sputtering PZT thin films for ferroelectric memories

Abstract

This paper describes amorphous Pb(Zr, Ti)O₃ (PZT) thin films deposited by cosputtering Pb(Zr_0.5 Ti_0.5)O₃ and PbO targets. By optimizing the amount of the excess Pb and the deposition temperature, PZT thin films with a single perovskite phase were obtained successfully on Ir substrates and Pt substrates at 520°C. 250-nm-thick PZT films crystallized by rapid thermal annealing (RTA) at 600°C for 20 s exhibited excellent ferroelectric properties: a coercive voltage of 1.0 V, a remanent polarization density of about 40 μC/cm², and a polarization switching endurance over 1x109 cycles. Although a heat treatment in a reductive ambient causes degradation of ferroelectric properties of PZT thin films, their degraded ferroelectric properties can be easily recovered from by a 1-min RTA in an oxygen at 400°C.     

Optically addressed ferroelectric memory and its applications

Abstract

Thin films of perovskite titanates can be composition-tailored to exhibit ferroelectric, pyroelectric, or piezoelectric properties, in varying degree of combinations, and thereby modulating their response when illuminated with light. This paper reviews the potential applications of photoresponse from lead zirconate titanate thin films. In ferroelectric materials, such as lead zirconate titanate (PZT), for example, the photoresponse shows a clear dependence on remanent polarization. The main highlight of the paper is a review of the concept of optically addressed ferroelectric memory and identification of its high impact applications. Incidence of energetic laser beam pulses gives rise to two different classes of phenomena: first, a thermally triggered piezoelectric/pyroelectric response and second, an optoelectronic response. Optimizing the device geometry and selecting the illumination characteristics, one can easily control the dominating mechanism in a device. The optoelectronic effect emerges at a relatively lower incident beam power (≤2 mW/μm²) and can be as fast as the duration of the pulse (≤10ns), and therefore, is directly relevant as a non-destructive read-out signal from optically addressed ferroelectric memory. The optical NDRO signal offers itself as a unique tool that allows a non-destructive ‘probe’ for the capacitor, without causing any polarization switching in it, the characteristic artifact of the electrical destructive readout (DRO) measurement technique. Furthermore, the polarization dependent photoresponse could also be exploited as a non-destructive evaluation tool for mapping the domains in ferroelectric films, to generate fundamental understanding of the domain dynamics (generation, growth, movement, etc., under applied field, illumination, and/or temperature) in such thin films. In addition, with a high fidelity analog nature of the remanent polarization, the highly parallel, high speed photoresponse output from such optically addressed memories may be ideally suited for high performance computing applications especially involving image processing, high speed communication and parallel processing with architectures, such as large scale artificial neural networks.     

IPM智能功率模块电路设计及其在有源滤波器装置中应用

智能功率模块IPM(Intelligent Power Module)功能完善,可靠性高,具有集成度高、体积小的特点。在有源电力滤波器装置中使用IPM可以简化装置的主电路,提高系统整体可靠性。IPM电路设计主要包括驱动电路部分、缓冲吸收电路部分以及保护电路部分。IPM驱动方案由驱动电源和光耦接口电路组成,根据模块的设计要求,给出了一种典型的高可靠性的IPM外部驱动方案。由于关断浪涌电压和续流二极管恢复浪涌电压的存在,IPM上会产生过电压,必须设计相应的缓冲吸收电路,来减少开关损耗,充分利用功率器件的功率极限。通过分析3种常见的缓冲电路,给出了相应的适用范围。IPM保护电路由模块内部的保护电路和外围辅助保护电路组成,外围保护电路的设计基于对IPM故障信号的处理。通过使用IPM构建有源滤波器的逆变电路,分析了其在有源滤波器装置中的应用。     

A novel cell and array architecture for fet-type Ferroelectric nonvolatile memories

Abstract

A novel cell using a depletion type Metal-Ferroelectric-Semiconductor FET (MFSFET) as storage device is proposed. Its operations are based on a Metal/Ferroelectric/N-Si/P-Si (MFNP) structure. Read and write disturbance can be avoided in an array of such cells. The basic operations of device have been simulated.     

本安电路参数设计及元件要求简介

介绍了本质安全电路参数设计及主要文件要求。     

基于虚拟软件的电路设计与测试技术

电路设计与测试虚拟化是基于某些专门的仿真软件完成的 ,是电路测试概念与手段的变革 .EWB具有界面友好、操作简便 ,实用性强等优点 ,本文以其为例 ,简介电路设计与测试虚拟化软件的功能及其操作技巧     

室内照明线路设计施工中常见的问题与对策

人工照明是现代建筑满足照度和装饰的最基本的手段,电气照明是当前实现人工照明的主要手段。电气照明具有灯光稳定、易于控制、调节、使用安全、经济的优点。是实现安全生产,保障人身视力健康的重要条件。合理地进行照明设计和施工,是建筑物保障其完善功能的必要条件。照明线路是传递照明所需电能的载体。在室内照明线路的敷设中,影响照明质量的一些关键问题,需要设计和施工人员注意。     

LW4—220型断路器压气特性优化设计及分析

本文对剪刀式传动系统进行分析并推导出传动比计算式及液压环形间隙缓冲计算式;在压气特性优化设计中采用了正交设计法及目的规划法;最后对进行过的几次断流试验作了简单的分析小结。     

电路设计与电气防爆问题探讨

本文主要介绍了电气控制电路设计的一般设计规则、基本步骤以及电气设备防爆类型与措施,供广大同仁参考.     

DBD电路模型参数的测量与仿真分析

为了能够对介质阻挡放电(Dielectric Barrier Discharge,DBD)的物理机制有更深入的理解,目前国内外许多学者采用电路模型仿真与实验相结合的方法来对介质阻挡放电进行研究,它们通过结合实际的试验条件,提出了许多不同的电路仿真模型。本文在华中科技大学张庭提出的电路模型基础之上,通过实验和理论计算分别得到了试验装置的介质电容和气隙电容,对该模型进行了仿真,并对仿真结果和试验结果进行了比较。在保持电感L和电源频率f及幅值不变的情况下,讨论了当记忆电阻Rmen和记忆电容Cmen变化时,放电电流从单峰模式向多峰模式的演变规律。并对电流脉冲的变化情况与记忆电阻和记忆电容的关系进行了探讨,以期能够对DBD的放电机理有更深入的理解。     

电子镇流器半桥逆变输入电路分析与设计

电子镇流器半桥逆变输入电路决定整机工作频率,是影响开关功率管逆变的重要因素。通过对脉冲变压器及理想激励电流波形的分析,如何提高转换速率,阻尼振荡予以讨论,指出目前存在的设计误区,做出减少共态导通与开关损耗的新设计。     

Circuit implementation and model of a new multi‐scroll chaotic system

In this paper, a multi‐scroll chaotic system from the improved Chua's system is proposed. Moreover, non‐linear dynamics are analyzed including phase‐space trajectories, bifurcation diagrams, Poincaré maps and so on. The most important thing is that we discovered phase‐space trajectories, bifurcation diagrams and Poincaré maps are unified and closely related, which can describe different aspects of the multi‐scroll chaotic system. Furthermore, the corresponding improved module‐based circuits are designed for realizing two to four‐scroll chaotic attractors, and the experimental results are also obtained, which are consistent with the numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

某220kV变电站跳位监视回路设计缺陷分析及改进

针对某220 kV变电站跳位监视回路的设计缺陷问题,通过对保护装置和断路器合闸控制回路的设计及接线原理进行分析,发现跳位监视回路存在监视盲区,导致控制回路断线时保护装置和后台未能正确提示并告警。对跳位监视回路的二次接线改进后,成功消除了跳位监视回路监视盲区的问题,提高了系统供电可靠性和安全稳定性。     

真空断路器弹簧操动机构优化设计与可靠性分析

在真空断路器弹簧凸轮操动机构中,其开断特性与合闸弹簧、分闸弹簧和触头弹簧是息息相关的,它们性能的优劣对真空断路器的安全开断起着极其重要的作用。因此对真空断路器弹簧操动机构进行优化设计,并对其合闸弹簧、分闸弹簧以及触头弹簧进行可靠性分析,通过对其强度-应力干涉模型的分析,确定其在一定工作时间内的可靠度,进而实现对其开断特性的可预知性。     

超级电容器应用设计

以超级电容器放电时端电压的变化为基础,推导出了其应用设计中容量、等效串联电阻、串并联个数的计算公式,介绍了国内外一些公司超级电容器产品的性能指标;并以数据存储电路系统、脉冲电路系统的应用设计为例,对超级电容器应用设计方法进行了研究,同时提出了应用中应注意的一些问题。     

CW1-2000智能型万能式断路器的可靠性试验研究与分析

通过对CW1－2000智能型万能式断路器的分析，提出了该产品可靠性特征量及指标。根据试验结果，对操作机构、欠压脱扣器和合闸电磁铁中的累积试验时间，累积故障数及平均无故障时间等数据进行了可靠性分析。结果表明：产生故障的主要原因是由振动和疲劳引起的，提出了改进措施。     

一次自动重合闸实验电路设计与实现

在实验室没有断路器的情况下,笔者构想一个模拟断路器,设计配套电路,并对设备技术参数进行选择、计算,将自动重合闸装置在实际线路上的运行情况及动作的物理过程再现出来,利于学生深刻理解一次自动重合闸的工作原理,认识其在减少停电时间,提高供电可靠性方面的作用,构建自动重合闸装置工作的物理过程。实验效果显著。     

DCA准眢能测量电路设计

文中实现了直流电流的准智能测量,即无档测量,且在0-20A测量范围内做到内阻恒为0.01Ω。