铁电随机存储器的研究进展

铁电薄膜与半导体集成技术相结合而发展起来的铁电存储器．以其高密度、高速度、非易失性及抗辐射性而大大优于目前任何一种半导体存储器。该文介绍了铁电存储器的存储原理、特点、基本存储单元、研究进展、应用及存在的问题，并指出1T结构的铁电随机存储器(FRAM)将会成为下一代随机存储器。     

新型非易失性存储器的抗辐射能力研究进展

通过研究铁电存储器、磁性随机存储器、相变存储器和阻变存储器4种新型非易失性存储器的抗辐射能力,总结了每种非易失性存储器的总剂量效应和单粒子效应。针对总剂量效应和单粒子效应进行了对比与分析,得到了目前的新型非易失性存储器的抗辐射能力仍然取决于存储单元以外的互补金属氧化物半导体(CMOS)外围电路的抗辐射能力。该结论为抗辐射非易失性存储器的研究提供了参考。     

铁电存储器在FPGA中应用的初步研究

提出了一种全新的基于铁电存储器FeRAM编程的非挥发FPGA思想(概念)，它主要是针对基于SRAM的FPGA的掉电挥发性问题提出的。文章在采用传统2T—2C结构的铁电存储单元的基础上完成数据的编程操作，并进一步对上述单元进行了电路和时序上的调整设计，提出了在FPGA工作环境下虽破坏性读出但无需回写的铁电存储单元。通过对文中提及的两种单元电路的仿真模拟，实现了编程数据的摔电保护、上电恢复的非挥发功能，初步验证了基于FeRAM编程的非挥发FPGA思想的正确性和可行性。     

钛酸铅铁电薄膜电容器及其存储单元的制备

用溶胶－凝胶方法制备出了ＰｂＴｉＯ３（ＰＴ）铁电薄膜电容器，设计了相应的非易失存储单元。介绍了ＰＴ溶胶的络合、水解成胶反应，铁电薄膜电容器的制备工艺，存储单元电路设计及工作原理。     

基于氧化钨的8 Mb高密度阻变存储器设计

设计了一款基于氧化钨的8Mb高密度阻变存储器,采用单晶体管开关、单电阻(1T1R)的存储器单元结构,设计了完整的存储单元、行列译码器、写驱动和灵敏放大器等关键模块。存储器芯片采用HHNEC 0.13μm 1P8M CMOS工艺流片。仿真结果表明,在8F2的高密度存储单元面积下,该存储器可实现准确的数据写入和读出功能。     

一种4k位串行铁电不挥发存储器的VLSI实现

文章提出了一个基于VLSI的4k位串行铁电不挥发存储器的实现方案。该电路采用2T－2C的存储单元设计,针对铁电电容的读出和写入的电流电压特性设计了相应的读写时序,给出了状态机的描述和相应的电路实现。该电路与通用的E^2PROM 24C04在接口、电学特性上完全兼容,可以在24C04的电路应用中直接代替之。     

铁电电容模型及其在铁电存储器中的应用

近年来,集成铁电学（integrated ferroelectrics)迅速发展。铁电体是一种特殊的电介质,在不存在外场的情况下,它仍然可以保持一个自发的极化强度。其极化方向在外电场的作用下可以发生反转,表现出特殊的非线性介电行为,即电滞回线。文章讨论了铁电电容模型的SPICE实现。首先介绍电容模型的实现,然后结合2T－2C铁电存储单元的工作原理,验证了该模型。最后,给出了一个完整的32位铁电存储器的电路仿真结果。该结果可以非常容易地推广到更大容量的铁电存储器中。     

铁电存储单元的设计和测试

基于被应用于实际设计之中的统一的铁电器件模型，详细讨论了２Ｔ ２Ｃ组态的铁电破坏性读出存储器单元的设计。在此基础上，设计和制造了分立元件的单元测试电路。通过与普通电容的对比实验，证实了铁电破坏性读出随机读取存储器与普通随机读取存储器不同的工作原理和模式。进而获得了被测ＦＲＡＭ单元的特性波形和铁电材料存储特性的有关数据。这些工作为进一步进行大规模铁电存储器的研究作了准备。     

铁电存储器研究进展

近几年来,铁电存储器研究取得了很大进展.铁电存储器因其所具有的许多优越性和良好的应用前景而受到人们的广泛关注和重视.本文介绍了铁电存储器的工作原理及设计与制作方法.并对其研究现状及进一步发展趋势作了简要的评述.     

钛酸铅铁电薄膜电容器及其存储单元制备

用溶胶－凝胶方法制备出了ＰｂＴｉＯ３（ＰＴ）铁电薄电容器设计了相应的非易失存储单元。介绍了ＰＴ溶胶的络合、水解成胶反应存储单元电路设计及工作原理。     

新型不挥发非破坏性读出铁电存储器(MFS)

长期以来，人们认为铁电场效应管是单晶体管、不挥发、非破坏性读出存储器的基本结构。铁电场效应管的基本结构为金属／铁电／半导体（MFS）结构。MFS存储器与其它不挥发性存储器相比在数据传输速率、疲劳特性和工作电压等方面有更大的优点。本论文简单地论述了MFS存储器的结构、工作原理和制备方法。     

Facile and solvent-free fabrication of highly oriented ferroelectric copolymer thin films and its application in ferroelectric field effect transistors

An environmentally friendly and solvent-free method was reported for fabrication of ferroelectric copolymer P(VDF-TrFE) thin films directly from their molten mass. Friction-transferred poly(tetrafluoroethylene) (PTFE) templates were used for epitaxy during solidification process. The obtained films showed highly-oriented crystallite structure and improved degree of crystallinity. Electrical measurement indicated that these films presented good ferroelectric property with remnant polarization comparable to those solution deposited and epitaxially processed films. A ferroelectric field effect transistor (FeFET) was constructed with one oxide semiconductor as an active layer and P(VDF-TrFE) as a ferroelectric layer. The memory device showed an ON/OFF ratio as high as 10⁵ and good retention performance during the whole experimental duration. This work developed a new route for environmentally friendly fabrication of organic ferroelectric devices.     

集成铁电存储器——新型快速,抗辐照,非挥发性存储器件

本文介绍了铁电存储器的原理，对非挥发性铁电存储的研究和开发情况作了综述。并就制约着铁电集成器件真正商业化的若干铁电薄膜材料物理方面关键问题作了分析。首先提出了在铁电集成器件工艺中还存在着综合优化问题。最后，对铁电存储器的未来作了预测。     

用于铁电透镜相控阵天线的铁电移相器有限元分析

简要介绍一种低成本铁电透镜相扫天线的工作原理及其基本特点。利用有限元方法对铁电介质加载波导移相器进行了分析,给出了计算结果,并通过一个四级阻抗匹配的铁电移相器设计实例讨论了铁电移相器设计中几个值得注意的问题。     

新型集成微麦克风和扬声器的结构设计

在现有的硅基Ｐｂ（Ｚｒ,Ｔｉ）Ｏ３（ＰＺＴ）铁电薄膜的制备工艺基础上,提出了一种以ＰＺＴ悬臂式振膜为核心的集成微麦克风和扬声器结构,对其进行了优化设计。对微麦克风和扬声器的灵敏度和声输出进行了理论计算。并比较了基于ＰＺＴ和ＺｎＯ两种材料的微麦克风和扬声器的性能差异。     

Enhancing pyroelectric and ferroelectric properties of PVDF composite thin films by dispersing a non-ferroelectric inclusion La2O3 for application in sensors

Thin films consisting of non-ferroelectric inclusions of La₂O₃ dispersed in a polymer matrix of polyvinylidene difluoride (PVDF) were prepared by the spin-coating method. It was found that the pyroelectric coefficient and remanent polarization of the composites were significantly improved to reach 42 μC/m² K and 84 mC/m², respectively. The enhancement of the measured coefficients in the composites can be achieved by introducing a very small amount (3 wt%) of La₂O₃. The figure of merit for material sensitivity, F_D has also improved from 69 to 86 μC/m² K¹. A local field in the inclusion site was shown to facilitate the poling procedure. A simple Maxwell–Wagner model in which the dc conductivity of the inclusion site was taken into consideration showed a good agreement with the obtained pyroelectric and ferroelectric properties.     

Effect of the film thickness on the crystal structure and ferroelectric properties of (Hf0.5Zr0.5)O2 thin films deposited on various substrates

In this work, the effect of the film thickness on the crystal structure and ferroelectric properties of (Hf_0.5Zr_0.5)O₂ thin films was investigated. The thin films were deposited on (111) Pt-coated SiO₂, Si, and CaF₂ substrates with thermal expansion coefficients of 0.47, 4.5, and 22×10⁻⁶/°C, respectively. From the X-ray diffraction measurements, it was found that the (Hf_0.5Zr_0.5)O₂ thin films deposited on the SiO₂ and CaF₂ substrates experienced in-plane tensile and compressive strains, respectively, in comparison with the films deposited on the Si substrates. For films deposited on all three substrates, the volume fraction of the monoclinic phase increased with increasing film thickness, with the SiO₂ substrate having the lowest monoclinic phase volume fraction at all film thicknesses tested. The grain size of the films, which is an important factor for the formation of the ferroelectric phase, remained almost constant at about 10 nm in diameter regardless of the film thickness and type of substrate utilized. Ferroelectricity was observed for the 17 nm-thick films deposited on SiO₂ and Si substrates, and the maximum remanent polarization (P_r) value of 9.3 µC/cm² was obtained for films deposited on the SiO₂ substrate. In contrast, ferroelectricity with P_r=4.4 µC/cm² was observed only for film on SiO₂ substrate in case of 55 nm-thick films. These results suggest that the films under in-plane tensile strain results in the larger ferroelectricity for 17 nm-thick films and have a ferroelectricity up to 55 nm-thick films.     

Memory and ferroelectric photovoltaic effects arising from quasi-reversible oxidation and reduction in porphyrin entrapped aminopropyl-silicate films

We report non-zero-crossing bipolar current–voltage characteristics, and ferroelectric photovoltaic-like effects in flexible organosilicate polymer films. These film are composed of 5,10,15,20-terakis(4-hydroxyphenyl)-21H,23H-porphine and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine embedded in (3-aminopropyl)trimethoxysilane network. The films were prepared on gold coated bi-axially oriented polyethylene terephthalate (BoPET) substrate by sol–gel method. For electrical characterizations, gold (40 nm) was deposited on the film for using as top contact. The current–voltage characteristics of devices, BoPET/gold/film/gold, have shown hysteresis with two current peaks in opposite direction. The open circuit voltage (∼±0.8 V) and short circuit current (∼±6 μA) that arise from non zero-crossing current–voltage characteristics have been utilized to read the ON and OFF states for non-volatile memory application of the devices. Furthermore, the studies on redox induced polarization in the polymer matrix by charge–voltage, capacitance–voltage, and positive-up and negative-down measurements reveal the characteristics of ferroelectric materials. The photovoltaic behaviors such as short circuit photocurrent were studied under blue LED source after polarizing BoPET/gold/polymer film/gold device by electric field as done for classical ferroelectric materials. The observed memory, ferroelectric-like and photovoltaic effects of organosilicate film were explained from quasi-reversible oxidation and reduction of moisture that diffuse into the film and dissociate to ions under applied electric field. These findings are important for designing new solution processible polymer materials which could find applications in flexible memory, ferroelectric based memory and switchable photovoltaic effects.