摘要:

Ferroelectric Pb0.9La0.1Zr0.2Ti0.8O3(PLZT) thin film capacitors with symmetrical La-Sr-Co-O top and bottom electrodes have been grown on [001] Si with a Yttria stabilized zirconia (YSZ) buffer layer and on SiO2Si substrates. A layered perovskite “template” layer (300–500 Å thick), grown between the YSZ buffer layer or the SiO2layer and the bottom La-Sr-Co-O electrode, is critical for obtaining the required orientation of the subsequent layers. The fatigue, retention and aging characteristics of these new structures are quite desirable for nonvolatile memory operation. Preliminary studies show that this ferroelectric performance obtained in large (50–100 μm diameter) capacitors can be replicated in smaller capacitors (down to 4 μm diameter) processed by ion milling.

ISSN:1058-4587    

DOI:10.1080/10584589408017007

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

PZT thin films have been prepared via a sol-gel route using standard butoxide and acetate precursors. The solution compositions were modified by the addition of acetylacetone in 2 methoxyethanol, which has the effect of changing the solution complex and therefore its deposition and drying characteristics. Varying amounts of excess lead were included in some cases. The films were prepared by spin coating onto Pt/Ti electroded silicon with an intermediate barrier layer of either boron phosphate silica glass (BPSG) or thermal silicon oxide and the resulting samples subjected to a range of thermal annealing conditions in an oxidising atmosphere. Several methods have been investigated including two regimes using rapid furnace annealing (RFA) up to 700°C and slow annealing at 450°C in air. The latter method yielded highly (111) oriented and crack-free perovskite films with no evidence of other orientations, whereas the former route showed the presence of (100) and (110) orientations. The correlation between the thermal anneal method and orientation will be discussed. Surface electrode dots have been evaporated onto the film to allow electrical measurements. The ferroelectric and fatigue properties of these films have been assessed with respect to non-volatile memory applications. The implications of film quality and thermal processing on the overall ferroelectric performance will be discussed.

ISSN:1058-4587    

DOI:10.1080/10584589408017008

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of deposition temperature on the properties of thin films of sputtered lead-zirconate-titanate (PZT) have been studied for ULSI DRAM storage capacitor dielectric applications. The films were deposited by reactive dc magnetron sputtering from a multi-component target. The grain size for the films deposited at 400°C was found to be less than 1000 Å, while it was ∼ 10–30 μm for films deposited at 200°C. Small grain-sized material is desirable since it leads to better cell-to-cell uniformity in terms of charge storage capacity and other electrical and reliability properties. The optimum lead compensation was found to increase as the deposition temperature (Tdep) increased. Leakage current density stays fairly constant asTdepis varied. As-deposited films, with a deposition temperature of 500°C, were rich in the perovskite phase and showed a high charge storage density of 11.2 μC/cm2and a low leakage current density of 5.1 × 10−7A/cm2(both at 1.5 V). This implies the possibility of eliminating the high temperature crystallization-annealing step.

ISSN:1058-4587    

DOI:10.1080/10584589408017009

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Electrical characteristics of metal-insulator-semiconductor (MIS) capacitors of a variety of ferroelectric materials like lead zirconate titanate (PZT), lead titanate (PT) and barium magnesium fluoride (BMF) on p-silicon have been studied. PZT was deposited by r.f. magnetron sputtering from a composite target and PT from co-evaporation. The films were annealed in oxygen atmosphere in the temperature range 550–700°C for various times. PZT and PT films which are directly deposited on silicon showed low effective dielectric constant.10For normal applied bias voltages (±5 V), the C-V curves did not show significant hysteresis. The effective dielectric constant was improved significantly by the incorporation of a buffer layer. BMF film was deposited in ultra high vacuum on a heated substrate and the film was encapsulated by a zirconium oxide layer. The C-V curves for these MIS capacitors shows hysteresis and the direction of hysteresis corresponds to ferroelectric polarization.

ISSN:1058-4587    

DOI:10.1080/10584589408017010

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Pb(Zr0.53Ti0.47)O3(PZT) thin films were deposited on Pt and RuO2coated Si and MgO substrates using the sol-gel process. Fatigue and retention tests were performed on these samples. The films grown on RuO2electrodes are fatigue-free up to nearly 1011cycles. Their retention life-time extrapolates to more than 1010seconds. The fatigue behavior of films grown on Pt electrodes depends on the PZT film orientation. Highly oriented (001) PZT films maintain 50% of their initial P*r-P⁁r value after 1011cycles. The randomly oriented films maintain less than 3% of the initial P*r-P⁁r value after 1011cycles. However, the retention life-time of both highly oriented and randomly oriented PZT films grown on Pt electrodes extrapolates to higher than 1011seconds. It appears that fatigue of films grown on RuO2is mainly controlled by the film/electrode interface. On the other hand, fatigue of films grown on Pt appears to depend on both the film/electrode interface as well as on bulk effects.

ISSN:1058-4587    

DOI:10.1080/10584589408017011

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The dielectric and ferroelectric properties for Au/Pb(Zr,Ti)O3/YBa2Cu3O7−xheterostructures at low temperatures are reported. The fatigue behavior and the ferroelectric switching effect for the structures are also investigated. The PZT/YBCO thin film heterostructures were deposited on MgO(100) substrates by laser ablation. The ferroelectric and dielectric properties and optical response of the oriented PZT films with different thicknesses have been studied over the temperature range from 20 K to 300 K. The dielectric loss of the structure was found to decrease by an order of magnitude when the YBCO bottom electrode became superconducting. A very low fatigue rate of the structure has also been obtained belowTcof YBCO layer.

ISSN:1058-4587    

DOI:10.1080/10584589408017012

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The Ferroelectric Space Charge (FESC) Memory is a technique to achieve Non-Destructive Read-Out (NDRO) of a ferroelectric memory that employs standard metal-ferroelectric-metal memory capacitors. The NDRO technique allows the polarization state of the capacitor to be read without altering the polarization. This provides the advantage that the memory capacitor is not subjected to the destructive read/rewrite cycle commonly employed in ferroelectric memories, so the lifetime of the device is limited only by the number of times the memory is written. In addition, the NDRO avoids the period of data volatility in the time interval between the read pulse and the subsequent rewrite of the data. The FESC NDRO approach utilizes changes in the dielectric response of the ferroelectric due to interactions between the internal space charges, the spontaneous polarization, and internal and external electrical potentials. The NDRO is implemented entirely in circuitry and does not require specialized ferroelectric devices. It has been proven in working breadboard circuits and hybrid memory modules. The FESC memory concept is the subject of several patents awarded to Draper Lab.

ISSN:1058-4587    

DOI:10.1080/10584589408017013

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Fast rising electrical fields cause switching of a ferroelectric material and induce electron emission from its surface. Moreover, this process is strongly related to the degree of polarization change in the material. Simultaneous observation of the switching current and the electron beam pulse demonstrate that electrons are emitted due to successive partial switching and even due to switching from the remanent to the saturation polarization state. Generally it has to be distinguished between the setting free of electrons by the fast polarization inversion and the extraction of the beam. Calculations show that the field at the sample surface is strongly bent due to the grid structure of the electrode. Consequently, low energy electrons are turned off and captured by the electrode. This can be avoided by introducing an additional extraction potential. Thus significant current amplitudes were achieved also from thin ceramic emitters down to 85 μm thickness. The experimental technique is described.

ISSN:1058-4587    

DOI:10.1080/10584589408017014

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper the organometallic chemical vapor deposition (OMCVD) of RuO2using the precursor ruthenocene, Ru(C5H5)2, will be discussed. Stoichiometric RuO2thin films with a specific resistivity of about 50 μΩcm were obtained both on strontium titanate and platinized silicon wafers at temperatures between 300–700°C. PbZr0.8Ti0.2O3thin films were in situ deposited onto these RuO2electrodes. The ferroelectric behavior of the films obtained on the RuO2electrodes is compared with those obtained on platinum electrodes. Attempts to deposit in-situ a RuO2top electrode on the PbZr0.8Ti0.2O3were unsuccessful.

ISSN:1058-4587    

DOI:10.1080/10584589408017015

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We compare several models of electrical breakdown, fatigue, and attenuation in ferroelectric thin (ca 100 nm) films.

ISSN:1058-4587    

DOI:10.1080/10584589408017016

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor