A new soft-error-immune DRAM cell using a stacked CMOS structure

A new VLSI memory cell is proposed that offers high immunity to alpha-particle-induced soft errors and a cell area comparable to a one-transistor memory cell. This memory cell consists of a pair of complementary MOSFET's and one capacitor. The PMOSFET is formed in an SOI film over the NMOSFET. Since both storage capacitor nodes are kept electrically floating in retention periods and one storage capacitor node is formed in a thin SOI film, an alpha-particle hit does not destroy the stored charge of this memory cell. It is sufficient for an SOI-PMOSFET to provide only three orders of magnitude ON/OFF current ratio. Experimental memory cells were fabricated using polysilicon film as an SOI film. Measuring them confirmed the main effectiveness of this memory cell.     

A new ferroelectric memory device, metal-ferroelectric-semiconductor transistor

The ferroelectric field effect has successfully been demonstrated on a bulk semiconductor (silicon) using a thin ferroelectric film of bismuth titanate (Bi4Ti3O12) deposited onto it by RF sputtering. A new memory device, the metal-ferroelectric-semiconductor transistor (MFST); has been fabricated. This device utilizes the remanent polarization of a ferroeletric thin film to control the surface conductivity of a bulk semiconductor substrate and perform a memory function. The capacitance-voltage characteristics of the metal-ferroelectric-semiconductor structure were employed to study the memory behavior. The details of the study together with a preliminary results on the MFST are presented.     

The effect of porous structure of PMMA tunneling dielectric layer on the performance of nonvolatile floating-gate organic field-effect transistor memory devices

In this paper, we used the low and high density porous structure of polymethylmethacrylate (PMMA) film as tunneling dielectric layer in the floating-gate organic field-effect transistor (OFET) memory devices. Compared to the thin/thick nonporous structure of PMMA tunneling layer, the porous structure of PMMA tunneling layer had positive impacts on the device performance of the floating-gate OFET memory devices. Moreover, it was found that the memory performance was also increased as pore density of PMMA film increased. The atomic force microscopy (AFM) results of both porous structure of PMMA film and pentacene film on porous structure of PMMA film revealed that high density porous structure of PMMA tunneling layer can produce larger tunneling area and more electron transfer paths between pentacene film and PMMA film, which resulted in high electron capture and release efficiency of the floating-gate OFET memory devices with porous structure of PMMA tunneling layer. In addition, our porous structure of PMMA tunneling layer as well as nonporous PMMA film has high electrical insulating property due to their semi-hollow structure film, which is favourable to maintain stable retention property. Eventually, the floating-gate OFET memory devices with high density porous structure of PMMA tunneling layer showed good nonvolatile memory properties with a large memory window of about 43 V, a high ON/OFF current ratio of about 10⁴, and stable endurance and retention properties. Our results provided a new strategy to achieve the high performance floating-gate OFET memory devices.     

Incorporation of non-conjugated polymer chain in conjugated polymer matrix: A new single step strategy for free standing non-volatile polymer memory

A new single step strategy for polymer memory materials has been explored using free-standing polypyrrole (PPy) film in which non-conjugated polymer chains are incorporated as trap states during synthesis. The PPy film was synthesized by the acidic oxidation of 2,2′:5′,2′′-terpyrrole at the air/water interface. The free-standing PPy films show large hysteresis along with current peaks in opposite directions during current voltage (I–V) characteristics. Hysteric behavior has been utilized to show rewritable memory effect. Furthermore, once electrical state (high or low conduction state) is set, the state is stable for months in ambient condition unless the state is reset by applying a voltage of opposite polarity. Thus the PPy film can be used as read once memory. The memory effect of the film is due to the conformational changes of non-conjugated polymer chains in the PPy matrix. The changes in conformation were confirmed from UV–Vis and FTIR spectra. This new strategy leads free-standing film based all organic polymer memory devices at ultra low cost.     

A poly-silicon TFT with a sub-5-nm thick channel for low-power gain cell memory in mobile applications

This work presents a gain-cell solution in which a novel ultrathin polysilicon film transistor provides the basis for dense and low-power embedded random-access memory (RAM). This is made possible by the new transistor's 2-nm-thick channel, which realizes a quantum-confinement effect that produces a low leakage current value of only 10/sup -19/ A at room temperature. The memory has the potential to solve the power and stability problems that static RAM (SRAM) is going to face in the very near future.     

Reliable Organic Nonvolatile Memory Device Using a Polyfluorene-Derivative Single-Layer Film

This letter describes the reversible switching performance of metal-organic-semiconductor (MOS) memory devices containing a polyfluorene-derivative single-layer film. The space-charge-limited current contributes to the switching behavior of WPF-oxy-F memory devices. The polyfluorene derivative reported here provides a significant advance to the field of organic semiconductors because it provides a type of organic memory material for nonvolatile memory devices. The following properties are responsible for its memory capabilities: its use of a single-layer film, a large on/off ratio (Ion/Ioff ~ 104), a long retention time (more than 10 000 s), acceptable thermal stability up to 120 degC, and an excellent device-to-device switching uniformity.     

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.     

Single-wafer polysilicon engineering for the improvement of over erase in a 0.18-/spl mu/m floating-gate flash memory

A new polysilicon grain engineering technology for the improvement of over erase in 0.18-/spl mu/m floating-gate flash memory has been developed with the use of single-wafer polysilicon processing, which makes it practical to use hydrogen as a process variable. The addition of hydrogen in polysilicon deposition significantly alters the reaction kinetics and produces polysilicon thin film of smooth surface, fine and uniformly distributed grains. Such a micrograin polysilicon possesses show excellent high-temperature stability. The benefits of the micrograin polysilicon are to be demonstrated through its improvement in over erase of a 0.18-/spl mu/m floating-gate flash memory.     

用于MFIS的ZrO_2薄膜的制备及特性研究

新型不挥发非破坏性读出铁电存储器金属 /铁电 /半导体器件结构中 ,存在着铁电薄膜与半导体衬底之间相互扩散、离子陷阱密度高、铁电薄膜难于直接淀积在硅衬底上、电荷注入等问题 ,因此在铁电薄膜与半导体之间增加一层合适的介质材料作为阻挡层是制备不挥发非破坏性读出铁电存储器的关键。文中研究了运用 SOL- GEL方法制备 Zr O2 介质层的方法 ,并且对制备的介质层的成份、结构、电特性进行了分析 ,为研制 MFIS作了准备。     

应用于FRAM的集成铁电电容的研究

集成铁电电容的制备是铁电存储器的关键工艺之一。该文采用射频(RF)磁控溅射法在Pt/Ti/SiO2/Si制备Pb(Zr,Ti)O3(PZT)薄膜,上下电极Pt采用剥离技术工艺制备,刻蚀PZT薄膜,形成Pt/PZT/Pt/Ti/SiO2/Si集成电容结构,最后高温快速退火。结果表明,这种工艺条件可制备性能良好的铁电电容,符合铁电存储器对铁电电容的要求。     

Room-temperature single-electron memory

This paper presents room-temperature operation, for the first time, of single-electron memory, in which one electron represents one bit of information. This is made possible by our new one-transistor memory configuration which has a very high charge sensitivity (conventionally, three circuit elements are needed). Another new technique, which facilitates single-electron memory, is the ultra-thin (3.4 nm) poly-Si film used for the active region, in which sub-10-nm-width current channels and storage dots are naturally formed. In the fabricated poly-Si TFT's a single electron is stored (or “written”) on a low-energy silicon island, and the number of stored electrons is counted (or “read”) by the quantized threshold-voltage shift. Single-electron memory provides the potential for new nonvolatile RAM's, suitable for mobile computers/communicators     

Dependence of electroluminescence efficiency and memory effect on Mn concentration in ZnS:Mn ACTEL devices

We have studied experimentally the dependence of the electroluminescence efficiency and the memory effect on the Mn concentration in ZnS:Mn ac thin-film electroluminescence (ACTEL) devices. With other device parameters kept approximately constant, we find that both luminous efficiency and memory loop width (expressed as a percentage of threshold voltage) exhibit a maximum as a function of Mn concentration. In addition, the memory loop width was found to depend on the ZnS film thickness. Under 1-kHz sine-wave excitation, the peak luminous efficiency in these devices was ∼0.5 l/W and occurred at ∼0.2-wt % Mn, while the peak memory loop width was ∼11 percent of the threshold voltage and occurred at ∼1.1-wt % Mn. The luminous efficiency and memory loop width were found to depend on the frequency and waveform of the excitation. The optimum Mn concentration chosen far a ZnS :Mn memory device depends on a compromise between a high luminous efficiency and a wide memory loop width. A key new result is that the average threshold electric field for electroluminescence increases logarithmically with Mn concentration beyond ∼0.2-wt % Mn. The above results suggest that the Mn doping is modifying the carrier-conduction process in the ZnS:Mn thin film.     

Self‐Powered Trace Memorization by Conjunction of Contact‐Electrification and Ferroelectricity

Triboelectric nanogenerator (TENG) is a newly invented technology that can effectively harvest ambient mechanical energy from various motions with promising applications in portable electronics, self‐powered sensor networks, etc. Here, by coupling TENG and a thin film of ferroelectric polymer, a new application is designed for TENG as a self‐powered memory system for recording a mechanical displacement/trace. The output voltage produced by the TENG during motion can polarize the dipole moments in the ferroelectric thin film. Later, by applying a displacement current measurement to detect the polarization density in the ferroelectric film, the motion information of the TENG can be directly read. The sliding TENG and the single‐electrode TENG matrix are both utilized for realizing the memorization of the motion trace in one‐dimensional and two‐dimensional space, respectively. Currently, the ferroelectric thin film with a size of 3.1 mm² can record a minimum area changing of 30 mm² and such resolution can still be possibly improved. These results prove that the ferroelectric polymer is an effective memory material to work together with TENG and thereby the fabricated memory system can potentially be used as a self‐powered displacement monitor.     

A novel MOS PROM using a highly resistive poly-Si resistor

A novel MOS electrically programmable read-only memory (PROM) using a highly resistive polycrystalline silicon (poly-Si) resistor as a memory element is proposed. In a highly resistive poly-Si, a new memory effect of an irreversible resistivity transition, from an initial highly resistive value to a low resistive one, is observed. The dependencies of the transition voltage and current, which cause the transition, on the poly-Si deposition conditions, are studied, and the deposition conditions suitable for MOS PROM fabrication are obtained. The transition voltage Vtcan be reduced down to 10 V by decreasing the poly-Si film thickness to 0.4 µm. The transition current is less than 10 mA. A 36-bit MOS PROM, using the poly-Si resistor as a memory element, is fabricated. The programming voltage used in this work is 25 V and the programming time per bit is less than 10 µs. The read access time is less than 300 ns. The programming voltage, however, can be reduced down to 15 V by decreasing the poly-Si film thickness and the series resistance in the circuit. The novel PROM has another advantage in that the poly-Si resistor is compatible with a conventional silicon-gate process.     

基于VO2/TiO2/FTO微结构的电压诱导相变存储器特性

相变存储器作为下一代具有竞争力的新型存储器,其基础和核心是相变存储介质.为了制备基于VO2薄膜的非易失性相变存储器,首先采用等离子体增强化学气相沉积法在氟掺杂二氧化锡(FTO)导电玻璃衬底上沉积一层厚度为100 nm的TiO2薄膜,再通过直流磁控溅射法制备VO2薄膜,并在TiOJFTO复合薄膜上形成VO2/TiO2/FTO微结构,用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、四探针测试仪和半导体参数测试仪表征分析微结构的结晶和非易失性相变存储特性.结果表明,N2和O2的体积流量比为60∶40时,在TiO2/FTO上可生长出晶向为〈110〉的高质量VO2薄膜,在VO2/TiO2/FTO微结构两侧反复施加不同的脉冲电压,可观测到微结构具有非易失性相变存储特性,在67,68和69℃温度下的相变阈值电压分别为8.5,6.5和5.5V,相比多层膜结构的相变阈值电压降低了约37％.     

Electrically Driven Random Laser Memory

The first electrically driven random laser diode with nonvolatile resistive random access memory functionality is designed and demonstrated. To illustrate the working principle, a metal–insulator–semiconductor structure based on Pt/MgO/ZnO thin‐film layers is fabricated on indium tin oxide glass. The current–voltage curve of the dual‐function random laser memory (RLM) device exhibits an excellent electrical bistability with a high ON/OFF current ratio (≈10⁷). The random lasing behavior is simultaneously demonstrated by using electrical pumping with the appearance of sharp‐peak emissions and a drastic enhancement of peak intensity. A wide angle‐dependent electroluminescence not only reveals its emitting advantage but also further supports the origin of random lasers. The first proof‐of‐concept presentation of RLM possesses several advantages of dual memory and lasing functions, which enables to open up new avenues to practical applications, such as light emitting memories for electrical and optical communication. This new horizon for the realization of all optical memories should therefore be able to attract academic as well as industrial interests. It is stressed here that the electrical reading of conventional memory array is usually in serial sequence, which limits the maximum data throughput. This hurdle can be overcome by optically readable memory devices.     

铁电存储器和IC卡

铁电薄膜与半导体集成产生了新一代非易失存储器，与传统的半导体非易失存储器比较具有突出的优点，是新一代ＩＣ卡的理想存储芯片。     

Limitation of the TiN/Ti layer formed by the rapid thermal heattreatment of pure Ti films in an NH3 ambient in fabricationof submicrometer CMOS flash EPROM IC's

In this study, the technical feasibility and limitation of the TiN film formed by the rapid thermal heat treatment (RTHT) in an ammonia ambient for the fabrication of 0.85-μm CMOS flash electrically programmable read only memory (EPROM) integrated circuits having a contact aspect ratio of approximately 1.5, were investigated. When the as-deposited thickness of the Ti film was less than 130 Å, all memory contacts exhibited an “electrically open” contact signature (>4750 Ω/contact). Transmission electron microscopy (TEM) cross section examination of a failed contact chain structure indicated that the failure mechanism could be a physical separation at the W-plug/silicon interface. For the Ti films with thickness between 130 and 240 Å, the contact resistance dropped to a value between 59 and 68 Ω/contact. Furthermore, the contact failure rate (contacts exhibiting “electrically open” signature) decreased as the thickness of the Ti film increased. In this case, the failure mechanism appeared to be the direct contact between the TiN layer and the silicon at the contact interface. This condition was created during the multistep nitridation process where approximately 240 to 250 Å of the Ti film was converted to TiN. For the memory devices having Ti films thicker than 240 Å, all memory contacts were electrically and mechanically stable, and exhibited equivalent or higher circuit yields compared to devices having a sputter deposited TiN/Ti bilayer film (control group)     

一种有机薄膜器件的制备及电存储特性

研究了一种金属/有机物/金属夹层结构有机薄膜器件的可逆电双稳特性.器件的阳极和阴极分别为真空热蒸发沉积的Ag和Al薄膜,中间介质层为真空热蒸发沉积的2-(hexahydropyrimidin-2-ylidene)-malononitrile(HPYM)有机薄膜.器件起始状态为非导通态,在大气环境下,可用正、反向电场进行信号的写入和擦除,表现为极性记忆特性.通过自然氧化的方法在底电极Al表面形成一层Al2O3薄膜层后,可使器件在不同的正向电压脉冲作用下达到不同的导电态,具有一定的多重态存储特性.同时,研究了不同的电极组合对器件电性能的影响,并通过紫外-可见吸收光谱以及喇曼光谱对器件界面进行表征.     

一种具有极性记忆效应的热可擦有机电双稳薄膜

报道了一种新型有机材料AOSCN(3，9-双(10-(二氰基亚甲基)-9-亚甲蒽基)-2，4，8，10-四硫杂螺[5，5]十一烷)，能与Cu形成具有电双稳特性的络合物，在6V电压下，薄膜发生从高阻态到低阻态的转变，跃迁时间小于30ns，驰豫时间小于1μs。若薄膜已发生高阻态到低阻态转变，高温热处理能使其恢复初始状态，这有望制成可擦写存储器。此外，在一定的工艺条件下，AOSCN与Cu和Al形成的金属-有机-金属(MOM)结，具有极性记忆效应。