摘要:

This invited paper presents the development work on integration of ferroelectric PZT capacitors with GaAs JFET devices for the fabrication of high density nonvolatile ferroelectric random access memories at McDonnell Douglas Electronic Systems Company. The paper will start with the preparation and characterization of various properties of the PZT films deposited by a sol-gel technique. It will be followed by the two approaches investigated for the formation of the p+ gates of GaAs JFETs: zinc diffusion and zinc implantation. The process compatibility and sequence of memory fabrication incorporating these two approaches will be described. The difficulties associated with the zinc diffusion approach will be discussed. Finally, the current effort in the integration of the PZT capacitors and the implanted GaAs JFETs will be presented.

ISSN:1058-4587    

DOI:10.1080/10584589208215736

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An apparent remanent signal seen by the application of voltage pulses to a Sawyer-Tower circuit is described. This 'remanent' is present for two pulses in the same direction when no remanent is expected. Variation of this signal with fatigue and ageing will be shown. Implications for memory circuits will also be discussed. Finally, several suggestions of possible mechanisms will be presented.

ISSN:1058-4587    

DOI:10.1080/10584589208215737

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

For nonvolatile memory applications, thin-film ferroelectric capacitors having high level of switching endurance (or ferroelectric fatigue limit) are required. This paper presents results that demonstrate improved endurance characteristics in our semiconductor-device quality, sol-gel derived lead zirconate-titanate (PZT) capacitors compared to other published results under comparable test conditions. These improved endurance characteristics have been obtained through continued developments in the PZT film deposition process, electrode metallization and capacitor fabrication techniques. Capacitors with top electrode of gold, platinum or palladium film and bottom electrode of platinum-titanium film were tested for endurance and related properties of transient current response, leakage current density, and small-signal capacitance-voltage and conductance-voltage characteristics. An alloying heat treatment of the gold or platinum top electrode to the PZT film significantly improved the endurance characteristics, apparently by decreasing the leakage current density. Capacitors with Pt top electrode that were alloyed at a lower than optimum temperature exhibited abnormal hysteresis loop changes after mid-109 cycles. Some evidence indicated that these changes were related to an increase in the leakage current density.

ISSN:1058-4587    

DOI:10.1080/10584589208215738

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Process for getting crack-free lead zirconate titanate (PZT) thin films micropatterned on Si substrate is demonstrated. The PZT film was deposited at temperatures below 300°C by magnetron sputtering using a ceramic target, and then etched before annealing. After annealed above 500°C to get perovskite phase, the PZT films shows no crack, while PZT films, not patterned, has cracks. This result can be explained as dissipation of stress energy by reduction of the lateral size of the film. The effects of processing parameters of reactive sputtering and annealing on the morphology of the PZT thin films are presented. Photo-assist etching of the PZT thin films using KrF laser is described, too.

ISSN:1058-4587    

DOI:10.1080/10584589208215739

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Lead zirconate titanate films are deposited using a planar multi-target sputtering system. This system consists of three metallic targets (Zr, Pb, Ti) and a rotating substrate holding pallet achieving a layer-by-layer growth of the material.Substrates used in this study were oxidised (100) Si wafers with thin sputtered Pt layer. At substrate temperatures of about 450°C “in situ” (i.e. without post-deposition annealing) deposition of single phase perovskite PZT was obtained. Deposition rate is 3.5 nm/min. At substrate temperatures of more than 500°C the layers are poor in lead. ZrTiO4 was identified by x-ray diffraction.The dielectric constant and losses of the PZT films varied from 400-500 and from 0.008-0.015 respectively. The films exhibited a hysteresis loop, remanent polarization measured was 7 μC/cm2 and coercive field strength 7.5*106 V/m.

ISSN:1058-4587    

DOI:10.1080/10584589208215740

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Sol-gel deposited ferroelectric capacitors composed of composite materials are electrically compared to homogeneous capacitors of the same nature the composites are derivatives of PT and PZT which are all built by a standardized process. The composites consist of doped and homogeneous interfaces in layered structures. The electrical results of hysteresis, dielectric constant, switching polarization measurements are used to analyze the samples.

ISSN:1058-4587    

DOI:10.1080/10584589208215741

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The application of ferroelectrics to EEPROM, nonvolatile SRAMs, and sub-0.5 micron channel length MOS field effect transistors for silicon VLSI can significantly simplify device fabrication process, increase circuit density, and enhance device performance.

ISSN:1058-4587    

DOI:10.1080/10584589208215742

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The developments in the integration of the SAW acousto-optic Bragg deflector of guided optical waves in the ZnO thin film on a Si substrate and Schottky diode photodetectors on the same Si substrate are reported. Thin film lens has been fabricated by making use of a gradual film thickness change, the refractive index dispersion of the fundamental mode on the film thickness, and the mode cut-off property of the higher order modes in the area of the concave shaped converging lens of the ZnO film. The guided optical waves SAW-Bragg deflected, mode selected and lens focused are detected by the Schottky diode photo-detector incorporated at the boundary between the ZnO film wave guide and the Si substrate. A couple of detectors are located one for deflected and the other for undeflected waves.

ISSN:1058-4587    

DOI:10.1080/10584589208215743

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Copious electron emission from a PLZT ceramic surface takes place either when the surface is illuminated with laser pulses, or when short high-voltage pulses are applied. In the latter case, charge densities of up to 5 μC/cm2 and current densities of some ten of amperes per square centimetre have been measured. Depending on the position of the material in its phase diagram, different behaviour of the emission has been observed. Consequently the pulsed electron beam varies with respect to its pulse length, its amplitude, and its risetime. Further investigation of these data related to the corresponding material state might be a good diagnostic method, interesting for the switching dynamics in the ns-region. Moreover, a direct application as a pulsed “Ferroelectric Electron Beam Source” is envisaged, as the emission does not rely on vacuum, but also works in low pressure gas or plasma. A maximum repetition frequency of 2 MHz has been established. An improvement of all data of the emitted electron beam seems feasible.

ISSN:1058-4587    

DOI:10.1080/10584589208215744

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Lead-zirconate-titanate thin films were successfully codeposited in a modest vacuum environment using a novel Gas Jet Deposition (GJD) process. The GJD process utilizes supersonic carrier gas jets to efficiently transfer the depositing species to substrates. High throughput, large coating area, and easy control of film stoichiometry make the GJD unique among various deposition techniques. GJD deposited PZT films exhibit excellent ferroelectric properties. Unlike other films reported in the literature, only one preferred orientation ([110]) was found in our films grown on Pt electrode. Fatigue tests show that the films are quite stable under ac voltage stress.

ISSN:1058-4587    

DOI:10.1080/10584589208215745

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor