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1.
R. R. Das P. Bhattacharya W. Pérez A. Morales Cruz Ram S. Katiyar S. B. Desu 《Integrated ferroelectrics》2013,141(1):305-311
Ferroelectric thin films of SrBi 2 Ta 2 O 9 (SBT) and (Sr 0.8 Ca 0.2 )Bi 2 Ta 2 O 9 (SCBT) were grown on platinized silicon substrates by using pulsed laser deposition technique. The effect of annealing temperature on the structural and electrical properties of the films was studied. Films were grown at 200 mTorr oxygen pressure with a constant substrate temperature at 500°C and annealed at different temperatures ranging from 700-800 °C in an oxygen ambient. X-ray diffraction data showed that as-grown films were crystalline nature. Atomic force micrographs showed that the grain size and surface roughness increased with increase in annealing temperature. The SBT films annealed at 800 °C showed ferroelectric properties with remanent polarization of 9.1 w C/cm 2 and coercive field of nearly 72 kV/cm. Whereas the SCBT films showed maximum remanent polarization of 7.3 w C/cm 2 with higher coercive field of 86 kV/cm. The higher coercive field in case of SCBT is attributed to the higher electronegativity of partially substituted Ca at Sr site. The dielectric constant increased with increase in annealing temperature and was attributed to the higher grain size. 相似文献
2.
Ferroelectric and dielectric properties were investigated for Ba0.8Sr0.2Ti(1?5/4x)Nb x O3 ceramics with different Nb2O5 concentrations. The relations between the ceramic structures and those properties were discussed. The Ba0.8Sr0.2TiO3 doping with 0.01mol% Nb2O5 appears to have a strong ferroelectric effect and better dielectric properties. The max permittivity (? max) is up to 7,521.3 and Ba0.8Sr0.2Ti(1?5/4x)Nb x O3 ceramics has higher permittivity even at room temperature. The permittivity presents broadened curves at large temperature ranges, which suggests a non Curie–Weiss behavior near the transition temperature. The diffuse phase transition coefficient (δ) for Ba0.8Sr0.2Ti(1?5/4x)Nb x O3 doping with 0.01mol% Nb2O5 reaches 0.098, and its P–E loop expresses a diffusing curve. The remanent polarization (2P r) and coercive field are 31.3 μC/cm2 and 10 kV/cm, respectively. The P–E loop presents a diffusing curve, which is relative to the relaxor characteristic. 相似文献
3.
Mitsue Takahashi Kazushi Kodama Toshiyuki Nakaiso Minoru Noda Masanori Okuyama 《Integrated ferroelectrics》2013,141(1-5):125-134
Abstract Retention characteristics of MFIS (metal-ferroelectric-insulator-semiconductor) structures have been investigated theoretically and experimentally. The simulated retention characteristics have indicated that reducing current through the ferroelectric layer is very effective to make the retention time long. In order to reduce the current through the ferroelectric layer, an MFIS with an improved ferroelectric layer and an M-I-FIS (metal-insulator-ferroelectric-insulator-semiconductor) have been investigated theoretically. Both of them have given good retention characteristics. Experimentally, retention characteristics of MFIS have been much improved by annealing, which is considered to suppress the current density in the ferroelectric layer, although those of M-I-FIS have been improved a little. 相似文献
4.
Kenji Katori Nicolas Nagel Koji Watanabe Masahiro Tanaka Hisayoshi Yamoto Hajime Yagi 《Integrated ferroelectrics》2013,141(1-4):443-450
Abstract SBT is a candidate as the ferroelectric material for large scale FeRAMs with the great advantages of less fatigue and better squareness in its P-E hysteresis curves, while SBT has the disadvantages of higher crystallization temperature that results in difficulties realizing a stacked structure cell and greater damage to its ferroelectric properties from forming gas annealing. This paper presents new top and bottom electrodes to eliminate these disadvantages for SBT. The remanent polarization decreases only slightly after forming gas annealing with the top electrodes of partially oxidized Ru. Ru-O top electrodes show no bubbles or peeling after forming gas. In order to achieve the stacked structure cell for SBT capacitors, a new diffusion barrier was developed. This new diffusion barrier withstands the high temperature annealing that is required to crystallize SBT films. With the new diffusion barrier hysteresis curves could be obtained with electrical connections through Si substrates. 相似文献
5.
Abstract Ferroelectric SrBi2(Ta, Nb)2O9 (SBTN) thin films were prepared by rf magnetron sputtering utilizing a multi-chamber type production tool (ULVAC CERAUS ZX1000). Accurate and dynamic compositional control results in excellent ferroelectric performances such as large 2Pr up to 15μC/cm2, fatigue free at least 109 cycles as well as good uniformity and process repeatability. These results indicate that the SBTN sputtering process is promising for ferroelectric memory production. 相似文献
6.
Lead based complex compounds, 0.8PbFe0.5− Ta0.5O3-0.2PbTiO3 (0.8PFT-0.2PT) ceramics, were prepared by the solid state reaction method, and the corresponding dielectric, ferroelectric
and ferromagnetic properties were investigated. As the PT phase was added to the PFT phase, the Curie temperature of 0.8PFT-0.2PT
ceramics increased. The ferroelectric P-E and ferromagnetic M-H hysteresis loops were observed at the same time. The ferroelectric
properties depend on the formation of the perovskite 0.8PFT-0.2PT phase; however, the ferromagnetic properties depend on the
formation of the pyrochlore Pb3FeTaO7 phase. 相似文献
7.
Influence of Ti-content in the bottom electrodes on the ferroelectric properties of SrBi2Ta2O9 (SBT)
Abstract Stress behavior, results of AES analysis and electrical properties of SBT in dependence of electrode structure and annealing conditions are discussed. Evidence for degradation of the electrical properties of SBT due to diffusion of Ti is presented. 相似文献
8.
Abstract Ferroelectric SrBi2Ta2O9 (SBT) capacitors were fabricated by the Electron-Beam-Induced Patterning process and their electrical properties were evaluated in detail. In this process, the dose of an electron beam irradiated on precursor films had a great influence on the electrical properties of the SBT capacitors. The appropriate electron dose significantly improved the electrical properties of the SBT capacitors although the excess electron dose made severe deterioration in the properties. The SBT capacitors fabricated with the optimum electron dose, 1.5 mC/cm2 for Sr:Bi:Ta = 0.8:2.2:2.0 solutions, exhibited excellent ferroelectric properties: a remanent polarization of 11.5 μC/cm2, a coercive field of 40 kV/cm, a leakage current of 8×10?8 A/cm2@ 1V and fatigue-free up to 1010 cycles. It seems that such improvements were caused by the adjustment of Bi contents in the films and the modification or the decompositon of precursors before heat treatment by electron beam irradiation. 相似文献
9.
In this study, crystalline structure, dielectric and impedance properties of SrBi2Ta2O9 (SBT) - based ferroelectric ceramics have been investigated with the substitution of wolframium/tungsten (W) onto the tantalum
site. Wolframium doped SrBi2(W
x
Ta1 − x
)2O9 (0.0 ≤ x ≤ 0.20) ceramics were synthesized by solid state reaction method. The X-ray diffractogram analysis revealed that the substitution
formed a single phase layered perovskite structure for the doping content up to x ≤ 0.05. The dielectric measurements as a function of temperature show an increase in Curie temperature (T
c
) over the composition range of x = 0.05 to 0.20. The W6 + substitution in perovskite-like units results in a sharp dielectric anomaly at the ferroelectric phase transition. Furthermore,
the dielectric constant at their respective Curie temperature increases with wolframium doping. Both enhanced Curie temperatures
and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased
“rattling space” due to the incorporation of the smaller tungsten cations. The dielectric loss reduces significantly with
tungsten addition. AC impedance properties vis-à-vis wolframium content has also been studied. 相似文献
10.
Koukou Suu Takeshi Masuda Yutaka Nishioka Noriakitani 《Integrated ferroelectrics》2013,141(1-4):407-418
Abstract SrBi2Ta2O9 (SBT) thin films were deposited on 6-inch Pt/Ti/SiO2/Si substrates by rf magnetron sputtering using a 12-inch ceramic SBT single target. It is found that several sputtering parameters such as argon (Ar) pressure and rf power were very effective to control the Bi content of SBT thin films which is essential for obtaining good ferroelectric properties. 相似文献
11.
Abstract Bismuth-layer-structured ferroelectric thin films, SrBi2Ta2O9 and Bi4Ti3O12, have been prepared by laser ablation method on both Pt sheets and Si wafers at low temperatures of 400 ~ 500°C. These thin films have been characterized by XRD, XPS, AFM, C-V, D-E hysteresis and J-V measurement. SrBi2Ta2O9 thin films have a good (105) preferential orientation, and Bi4Ti3O12 thin films have (117) and c-axis orientation on these substrates. Ferroelectric film-SiO2-Si structures show good C-V hysteresis curve owing to Si surface potential controlled by the D-E hysteresis. D-E hysteresis is obtained in Bi4Ti3O12 thin film prepared on Pt sheet, and the remnant polarization and the coercive force are 7.5 μC/cm2 and 72 kV/cm, respectively. 相似文献
12.
Degradation mechanisms of SrBi2Ta2O9 ferroelectric thin film capacitors during forming gas annealing
Walter Hartner Peter Bosk Günther Schindler Herbert Schroeder Rainer Waser Christine Dehm 《Integrated ferroelectrics》2013,141(1-4):341-350
Abstract The effects of annealing in forming gas (5% hydrogen, 95% nitrogen; FGA) are studied on spin coated SrBi2Ta2O9 (SBT) thin films. SBT films on platinum bottom electrode are characterized with and without platinum top electrode by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), High Temperature X-Ray Diffraction (HT-XRD) and Secondary Ion Mass Spectrometry (SIMS). High Temperature X-Ray Diffraction (HT-XRD) of blanket Ti/Pt/SBT films in forming gas revealed that the bismuth layered perovskite structure of the SBT is stable up to approx. 500°C. SIMS analysis of Pt/SBT/Pt samples annealed in deuterated forming gas (5% D2, 95% N2) showed that the hydrogen accumulates in the SBT layer and at the platinum interfaces next to the SBT. After FGA of blanket SBT films, tall platinum-bismuth whiskers are seen on the SBT surface. Performing the FGA of the whole Pt/SBT/Pt/Ti stack, two different results are found. For the samples with a high temperature annealing (HTA) step in oxygen after top electrode patterning, top electrode peeling is observed after FGA. For the samples without a HTA step after top electrode patterning, no peeling is observed after FGA. 相似文献
13.
Walter Hartner Günther Schindler Peter Bosk Zonimir Gabric Markus Kastner Gerhard Beitel 《Integrated ferroelectrics》2013,141(1-4):273-284
Abstract In this study, integration of an hydrogen barrier into a FeRAM process flow is investigated. It is reported in the literature that ferroelectric properties can be maintained after hydrogen annealing by using IrOx as a top electrode [16][17][18]. Advantage of materials like IrOx is less catalytic activity compared to Pt. However, we found that IrOx is not a promising candidate for top electrode barrier. (Pt)/IrOx/SBT/Pt capacitors are prone to shorting or exhibit high leakage. IrOx films are very easily reduced by reducing ambient which will result in peeling off. Also, IrOx films tend to oxidize Ti or TiN layers immediately. Therefore, other barrier materials or layer sequences like Ir/IrOx have to be considered. For protection of the entire capacitor an Encapsulation Barrier Layer (EBL) is required. In this study, LPCVD SiN is used. LPCVD SiN is a standard material in CMOS technology. Production tools are available and it is well known as hydrogen barrier. By modifying the deposition process and using a novel process sequence, no visual damage of the capacitors after SiN-deposition and FGA is seen. Also, no degradation of electrical properties after capacitor formation as well as after SiN-deposition and FGA is observed. However, after metal 1 and metal 2 processing, 2Pr values at 1.8V are reduced from 12μC/cm2to 2μC/cm2. Polarization at 5.0V is not affected. 相似文献
14.
J-P. Han X Guo C. C. Broadbridge T. P. Ma A. Ils M. Cantoni 《Integrated ferroelectrics》2013,141(1-4):65-72
Abstract The ability to form a high-quality buffer layer between the ferroelectric layer and the underlying silicon substrate is of critical importance. A suitable buffer layer must provide an acceptable electronic interface with the silicon substrate, and also must be able to prevent intermixing between the ferroelectric material and the underlying silicon, as well as prevent oxidation of the latter during device processing. This paper reports the properties of jet-vapor deposited silicon nitride and thermally grown silicon oxide as the buffer. Results from TEM, EDS, XRD and AFM micrographs will be presented, along with some electrical data taken from corresponding memory capacitor structures. 相似文献
15.
Kazumi Kato 《Integrated ferroelectrics》2013,141(1-4):93-100
Abstract The crystallographic orientation, microstructure and electrical properties of Sr2(Ta, Nb)2O7 thin films strongly depended on the composition (Ta:Nb). Post-annealing at 850°C was effective for the improvement of some properties. The thin films with relatively Nb-rich compositions, such as Sr2(Ta0.6Nb0.4)2O7 and Sr2(Ta0.5Nb0.5)2O7, showed the (0k0) preferred orientation. The Sr2(Ta0.5Nb0.5)2O7 thin film had a lamination layer structure after the post-annealing at 850°C for 6 min in oxygen. The characteristic microstructure originated in the crystallographic orientation of (0k0), which is the cleavage plane, and influenced electrical properties. The dielectric constant little change with the composition, however, the P-E hysteresis properties improved with the Nb content. 相似文献
16.
Rodriguez J.A. Remack K. Boku K. Udayakumar K.R. Aggarwal S. Summerfelt S.R. Celii F.G. Martin S. Hall L. Taylor K. Moise T. McAdams H. McPherson J. Bailey R. Fox G. Depner M. 《Device and Materials Reliability, IEEE Transactions on》2004,4(3):436-449
We report on the reliability properties of ferroelectric capacitors and memory arrays embedded in a 130-nm CMOS logic process with 5LM Cu/FSG. Low voltage (<1.5 V) operation is enabled by the 70-nm thick MOCVD PZT ferroelectric films. Data loss resulting from high temperature bakes is primarily caused by the imprint effect, which shows /spl sim/1.5 eV time-to-fail activation energy. Excellent bit endurance properties are observed on fully packaged memory arrays, with no degradation up to 10/sup 13/ write/read polarization switching cycles. Retention measured after 10/sup 12/ switching cycles demonstrates no degradation relative to arrays with minimal cycling. 相似文献
17.
采用粘结方法制备了一系列La0.8Sr0.2MnO3/Sn复合样品,分析了粘结剂与Sn含量对材料的相结构、形貌、电输运及磁电阻性质的影响。研究表明,母体相结构在粘结过程中没有改变,粘结剂主要分散在母相的表面/晶界处。材料的电阻率随环氧树脂含量的增加而增大。金属锡含量从5%增大到10%,样品的电阻率有所减小。在整个实验温度范围内,锡含量5%的样品没有出现绝缘-金属(I-M)相变;而锡含量10%的样品观察到了绝缘-金属(I-M)相变。所有样品都展示了明显的低场磁电阻特征,没有观察到本征峰的出现,低场磁电阻归因于自旋极化隧穿。高温下磁电阻效应不明显。 相似文献
18.
Abstract Bi–layered ferroelectric SrBi2Ta2O9 (SBT) films were successfully prepared on Pt/Ti/SiO2/Si substrates at 650°C by a modified rf magnetron sputtering technique. The SBT films annealed for 1 h in O2 (760 torr) and again for 30 min in O2 (5 torr) at 650°C show a average grain size of about 49 nm. The SBT films annealed at 65 0°C have a remanent polarization (Pr) of 6.0 μC/cm2 and coercive field (Ec) of 36 kV/cm at an excitation voltage of 5 V. The films showed fatigue–free characteristics up to 4.0 × 1010 switching cycles under 5 V bipolar pulse. The retention characteristics of SBT films looked very promosing up to 1.0 × 105 s. 相似文献
19.
Abstract The effects of sputtering conditions on the SrBi2Ta2O9 films deposited via a single-target RF-sputtering process were investigated in this study. It was found that the composition of targets significantly affected the phases and the composition of the deposited films. When the target contained high bismuth content, SrBi2Ta2O9 and a secondary Bi2O3 phase were formed. When the bismuth content in the targets was insufficient, a pyrochlore phase was produced. SEM images revealed that the composition of the targets also affected the surface morphology of the obtained films. When the target-to-substrate distance was increased, bismuth oxide was formed, which resulted in an increase in the leakage current. By optimizing the deposition conditions, the ferroelectric properties of SrBi2Ta2O9 films were improved. 相似文献
20.
Xinhua Zhu Tao Zhu Aidong Li Tao Yu Zhguo Liu Naiben Ming 《Integrated ferroelectrics》2013,141(1-4):195-203
Abstract In this work, the microstructural defects in SrBi2Ta2O9 (SBT) ferroelectric thin films were investigated at the atomic-scale by high-resolution transmission electron microscopy (HRTEM). A stacking fault with an extra inserted Bi-O plane normal to the c-axis was observed in SBT film with 10mol% excess bismuth prepared by metalorganic deposition. Edge dislocations with an average space about 3nm were observed at the small misorientation angle (8.2°) tilt grain boundary of SBT film with (001)-orientation prepared by pulsed laser deposition. The Burgers vector b for the edge dislocation was determined to be 1/2[110]α0, where α0 is the parameter of SBT unit cell. Chemical compositions of grains and grain boundaries in SBT films annealed in forming gas at 450°C and 500°C for 60 minutes were analyzed by using energy dispersive spectra at the nano-scale. Effects of the microstructural defects and microchemistry of the grain boundaries on the leakage current of SBT films are briefly discussed. 相似文献