Dielectric breakdown constitutes an important limitation in the use of insulating materials under high-voltage since it can lead to the local fusion and sublimation of the insulator. The role of electrical charge transport and trapping in alumina ceramics on their resistance to this catastrophic phenomenon is studied in this work. In polycrystalline materials, the interfaces between the various phases play a main role because they constitute potential sites for the trapping of electrical charges. The density and the nature of these interfaces can be controlled by the way of the microstructure parameters. So, the aim of the present paper is to highlight the influence of average grain size and intergranular phase crystallization rate on the ability of polycrystalline alumina materials to resist to dielectric breakdown. Thus, it is shown that the control of the process conditions (sintering aids content, powder grain size and thermal cycle) makes it possible to change not only the density (by the average grain size) but also the nature (by the crystallization or not of anorthite) of the grain boundaries. On one hand, at room temperature a high density of interfaces, due to low grain size and highly crystallized intergranular phase, leads to a high dielectric strength. On the other hand, at higher temperature (250 °C), the presence of vitreous intergranular phase makes it possible to delay breakdown. That behaviour is explained thanks to charge transport and trapping characterizations.

Alumina based ceramics for high-voltage insulation

Sintering of Ceramics - New Emerging Techniques

Low temperature (≤250 °C) deposition of aluminum oxide gate dielectric film using a new plasma enhanced metal‐organic chemical vapor deposition technique is described. With this technique, the substrate was not directly exposed to the plasma which minimizes radiation damage to both the substrate and the film. A dc potential was used to generate the plasma and the deposition of the film was achieved at extremely low plasma power (≤2 W) using trimethylaluminum and nitrous oxide reactant sources. The dielectric films were found to have a resistivity of ∼1014 Ω cm, dielectric constant of 7.9±0.2, and breakdown field ≥106 V/cm. A linear dependence of the film growth rate upon TMAl concentration was observed, indicating that the growth process is mass transport limited. Metal–oxide–semiconductor device structures were fabricated both on n‐Si and p‐InP substrates and the interface properties were evaluated by capacitance–voltage and Auger measurements. Both the devices show sharp interface with a minimum density...

Plasma enhanced metal‐organic chemical vapor deposition of aluminum oxide dielectric film for device applications

A novel high-density multilayer interconnect (HDMI) technology has been shown to provide very high functional densities and a fabrication platform for extremely compact and complex systems. The technology comprises an interconnect fabrication method for microelectronic circuits based on vacuum thin-film metallization and polymeric insulation between layers. The HDMI technology makes wafer-scale integration realistic by using a hybrid concept. Semiconductor devices can be built to the practical limit of reasonable yields, then regrouped on a substrate to achieve the desired level of integration. The technology is discussed in connection with photolithography, the effect of three-dimensional topography, alternatives for the definition of metal patterns, and the pattern of polymers. >

Fabrication of high density multichip modules

An Investigation of Guilt, Loss and the Separation-Individuation Process in Depression

An experimental procedure, which maintains an almost constant electric field at the insulator-silicon interface, is used to study the trapping of electrons injected into the Aluminum-oxide gate insulator of a MISFET structure. A simple model, consisting of a finite number of traps, located at or adjacent to the insulator-silicon interface is consistent with the experimental observations. Additional experiments in which the insulator current is measured directly allow the capture parameter of these traps to be calculated.

A study of charge trapping in the Al-Al2O3-Si, MIS system

Electron injection from a surface depletion region, over the surface barrier at an Al 2 O 3 -silicon interface is studied. The current passing over the barrier is measured by observing the rate of flat-band voltage shift as charge is trapped in the oxide. The data obtained is compared with the predictions of present models for charge injection. It is found that the so-called ‘lucky-electron’ model gives the most generally satisfactory agreement with the observations.

Charge injection from a surface depletion region—The Al2O3-silicon system

In the study of charge injection in the insulator-silicon system, variation of the electric field in the insulator, caused by charge trapping during a measurement, makes the interpretation and analysis of experimental data difficult. A measuring system and test device structure are described in which it is possible to monitor any change of the device threshold voltage and to adjust the applied gate voltage so as to maintain a constant electric field at the insulator-silicon interface. Experimental results will be presented which show the advantages stemming from this mode of operation.

J. Kolk

Papers

A study of charge trapping in the Al-Al2O3-Si, MIS system

Charge injection from a surface depletion region—The Al2O3-silicon system

An experimental technique for the study of non-avalanche charge injection or trapping in MIS structures