摘要:

The photo-induced metallo-organic decomposition (PIMOD) process has been successfully used to deposit a lithium niobate thin film acting as the gate oxide of the conventional MFSFET structure. The use of the low-temperature PIMOD process for thin film deposition has increased the device yields of the molybdenum liftoff for small area isolation. The electronic alteration of the properties of the ferroelectric gate transistor was previously shown to be caused by charges in the semiconductor being injected into the ferroelectric film. To prevent this problem, a thin SiO2buffer layer was thermally grown on the silicon substrate immediately before lithium niobate deposition. The silicon-lithium niobate interface was stabilized and the charge injection effect was eliminated due to the formation of the buffer layer. The channel current was shown to be greatly altered by the application of voltage pulses between the gate of the device and the substrate. Upon switching, the change in surface conductivity of the semiconductor was the same as that expected for ferroelectric switching.

ISSN:1058-4587    

DOI:10.1080/10584589408017021

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Ferroelectric Pb(Zr,Ti)O3films have been deposited by spin-coating techniques, applying a modified sol-gel process. The growth of the thin films as a function of processing has been investigated by structural analyses using XRD, XRF, SEM and TEM methods. The data are the basis for the discussion of the ferroelectric properties of the layers.

ISSN:1058-4587    

DOI:10.1080/10584589408017022

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Sol-gel processing was employed to deposit lithium niobate thin films on (100) silicon and platinum coated silicon. The films were annealed in oxygen at temperatures from 400 to 600°C. Characterization by X-ray diffraction and transmission electron microscopy showed crystallization to LiNbO3at 400°C. The films had a preferred (104) orientation with increasing (012) orientation as the annealing temperature increased. Electrical characterization of the films showed evidence for ferroelectricity via the hysteresis loop and C-V curves. These measurements along with small signal dielectric measurement and I-V characteristics indicated the presence of a linear capacitor at the film-silicon substrate interface which affected the overall electrical properties of the films.

ISSN:1058-4587    

DOI:10.1080/10584589408017023

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the past few years much attention has been directed to the use of ferroelectric materials as storage elements for nonvolatile memory products. All reliability data to date has used capacitors focusing on fundamental materials behavior and not on product performance. This paper will discuss the reliability of the FM1608S 64K and FM1208S 4K FRAM memories. In particular, fatigue performance out to 1012read/write cycles and retention performance out to 10 years will be presented. Short and long term retention behavior has been studied on product that has received over 1012read/write fatigue cycles. Short term retention is defined as the ability of the circuit to maintain a data state with no power applied for one second at 80°C. This test ensures the ferroelectric capacitor structure is storing the charge and not being influenced by the underlying CMOS refresh characteristics of the 2T/2C dynamic RAM cell design. Long term retention is defined as the ability of the circuit to maintain a data state with no power applied after having been stored at an elevated temperature (100°C to 150°C) for more than 1,000 hours. This will be shown to translate into use conditions well in excess of 10 years. The effect of voltage and temperature on fatigue read/write cycles has also been characterized and will be presented. Elevated temperature bakes were developed to remove defect populations from production 4K and 64K material. Subsequently, detailed activation energy experiments were done at temperatures ranging from 80°C to 200°C for more than 2,000 hours. An Arrhenius model was fit to the screened population. Calculated acceleration factors and associated failure mechanisms will be reviewed.

ISSN:1058-4587    

DOI:10.1080/10584589408017024

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We have observed a 40% increase in the piezoelectrical coupling of a PZT layer upon application of a 10 μs pulse of 17 × 104V/cm, which generated a polarization of 2.2 μc/cm2. A qualitative analysis of this data is given.

ISSN:1058-4587    

DOI:10.1080/10584589408017025

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A series of sol-gel derived La-doped PbTiO3-containing films was prepared on platinized Si wafers. The compositions investigated include PLT (0-28 mole % La) and PLZT (e.g., 9/65/35 and 12/80/20) films. These films were fired at temperatures ranging from 500 to 750°C. While most of the films were single-phase perovskite when fired at 700°C, lower firing temperatures (∼500°C) are sufficient to obtain crystalline PLT films, especially when the La content is more than 15 mole %. The paraelectric or ferroelectric character of the films as a function of La content is also addressed. In PLZT films, the Zr/Ti ratio affects the crystallization behavior and also the perovskite structure, i.e., either tetragonal or rhombohedral. Ferroelectric PLZT films exhibit high values of both dielectric constant (>700) and leakage current. The values of dielectric constant in the relaxor PLZT films are low, especially when compared to their bulk ceramic values (5000–10000). Paraelectric PLT films exhibit high values of dielectric constant (>500) and low leakage currents.

ISSN:1058-4587    

DOI:10.1080/10584589408017026

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Hillock formation during annealing of Pt/Ti electrodes has been an obstacle in the development of ferroelectric memories. In order to minimize hillock formation, a factorial experiment was carried out to investigate the effects of deposition temperature, and oxide, titanium, and platinum thicknesses. The appropriate metal thicknesses for minimizing hillock formation was found to depend on deposition temperature. The developed model predicted best results for a deposition temperature of 200–250°C, Pt thickness of 2000–2500 Å, and Ti thickness of ≤500Å. Without substrate heating, both thin Ti (≤500Å) and Pt (≤1000Å) were required for reduced hillock formation. Pt strain levels and crystallite size distributions were also determined for the films. Strain level correlated with the occurrence of hillocks. In addition, a broad crystallite size distribution appeared to give smoother films.

ISSN:1058-4587    

DOI:10.1080/10584589408017027

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

DRAM manufacturers face a tremendous challenge to keep the DRAM cell capacitance constant from generation to generation. The 256 Mb DRAM will certainly represent the last DRAM generation to use the standard storage dielectric materials consisting of silicon dioxide and silicon nitride. These materials cannot be shrunk further, and the capacitor area cannot be kept constant in a manufacturable cell. The most promising approach to keep cell capacitance constant in future DRAM generations, beyond 256 Mb, is to develop and integrate high dielectric constant materials.

ISSN:1058-4587    

DOI:10.1080/10584589408017028

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

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.

ISSN:1058-4587    

DOI:10.1080/10584589408017029

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Ferroelectrics and high-temperature superconductors have a variety of features in common which suggest similar mechanisms to be responsible for their occurrence. Ferroelectricity has been shown to be due to an onsite anharmonic electron-phonon interaction. In conventional superconductors, an attractive electron-phonon interaction compensates the Coulomb repulsion, thus leading to the paired electron state. For high-temperature superconductors it will be shown that again a mechanism based on electron-phonon interactions can lead to strong increases in the superconducting transition temperature Tc, depress the isotope effect and vary the gap to Tcratio. In spite of the close relationship between ferroelectrics and oxide superconductors, it is concluded that both phenomena are mutually exclusive.

ISSN:1058-4587    

DOI:10.1080/10584589408017030

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor