Thin Conductive Metal Research Articles

Quasi-static response of a sub-surface polarizable metal sheet

A simple analytical solution is given for a current point source in the vicinity of a thin metallic sheet conductor - which may have polarizable surfaces. The solution is obtained as the limit of a general layered model for a thin intermediate stratum having high conductivity while the thin coating strata have high (complex) resistivities. It is shown that the resulting composite thin sheet can also be treated at the outset employing effective boundary conditions which relate the jump or discontinuity in the tangential electric fields to the normal current flow on the two sides of the sheet. The appropriate discontinuity of the potential is also incorporated into the effective boundary conditions.

Electroplasticity and Electromigration

AbstractIt is known that an electric current can interact with dislocations in metals. Recent studies suggest that these interactions include current-induced dislocation motion and multiplication (electroplasticity) through both glide and climb mechanisms. Such interactions might be expected to effect both the mechanical properties and the electromigration behavior of the thin metal conductor lines used in integrated circuits. The mechanical properties would be directly modified through changes in dislocation density and mobility. Changes in microstructure and strength could affect electromigration lifetime and failure morphology. In order to investigate the effects of current-dislocation interactions, we conducted three sets of experiments in unpassivated aluminum conductor lines: First, a nanoindentation device was used to measure the mechanical properties of the lines during application of current densities up to 6 MA/cm2. Second, the mechanical properties of the lines were measured ex situ as a function of time in accelerated electromigration testing conditions. Third, the nanoindentation device was used to damage the lines at specific sites and damage morphology was examined during subsequent electromigration experiments by means of in situ scanning electron microscopy. To date we observe no direct effect of electric current on the mechanical properties of conductor lines and no clear correlation between mechanical damage and electromigration failure characteristics. Based on theoretical calculations and previous experiments on bulk samples, these results were not expected.

Multisensor array for pH, K +, Na + and Ca 2+ measurements based on coated-film electrodes

The construction of a multisensor array based on coated-film sensors is described. The pH, K +, Na + and Ca 2+ sensors studied so far show excellent electrode properties comparable to these of commercial ion-selective electrodes (ISE); the main attributes are the Nernst response over a wide concentration range, a good selectivity and short response times. They are similar, to coated-wire electrodes, but instead of a metal wire, a thin conductive metal layer manufactured in thin-film technology is used. It is shown that these transducers can be used for the development of a low-cost sensor for the determination of the ion activity in a simple way by potentiometric differential measurement. They can be applied to biomedical measurements, especially for blood analysis.

Coated film electrodes

The construction of coated-film electrodes is described. It is shown that they are miniaturizable, inexpensive, simple sensors for various cations and anions. They are similar to the coated-wire electrodes, but instead of a metal wire an extremely thin conductive metal layer manufactured in thin-film technology is used. Potassium and sodium electrodes studied so far show excellent electrode properties, i. e. near Nernst response over a wide concentration range, sometimes better than commercial ion-selective electrodes. Two film electrodes are used to develop a low cost sensor for the determination of the activity of ions in a simple way by potentiometric difference measurement; this solid-state sensor can be applied to biomedical measurements, especially for blood analysis.

Scanning tunneling microscopy and atomic force microscopy: application to biology and technology.

The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are scanning probe microscopes capable of resolving surface detail down to the atomic level. The potential of these microscopes for revealing subtle details of structure is illustrated by atomic resolution images including graphite, an organic conductor, an insulating layered compound, and individual adsorbed oxygen atoms on a semiconductor. Application of the STM for imaging biological materials directly has been hampered by the poor electron conductivity of most biological samples. The use of thin conductive metal coatings and replicas has made it possible to image some biological samples, as indicated by recently obtained images of a recA-DNA complex, a phospholipid bilayer, and an enzyme crystal. The potential of the AFM, which does not require a conductive sample, is shown with molecular resolution images of a nonconducting organic monolayer and an amino acid crystal that reveals individual methyl groups on the ends of the amino acids. Applications of these new microscopes to technology are demonstrated with images of an optical disk stamper, a diffraction grating, a thin-film magnetic recording head, and a diamond cutting tool. The STM has even been used to improve the quality of diffraction gratings and magnetic recording heads.

The Contributions of Metallurgy and Materials Science to the Evolution of Solid-State Electronics

The following three examples have been chosen to highlight some of the contributions of metallurgy and materials science in the development of solid-state electronics: (1) growth of high-purity, macroscopically dislocation-free silicon crystals; (2) elimination of electromigration in thin metallic conductors; and (3) minimization of growth- and processing-induced defects in silicon.

Solar cells fabricated by ionised-cluster beam technology

It is shown that ionised-cluster beam deposition and epitaxial techniques are useful for the fabrication of photocells. A thin layer of single-crystal silicon and a very thin conductive metal film made by these techniques are used to obtain wide-spectrum sensitivity of the cells. The p-n junction diode has been made by n-type silicon epitaxy onto a p-type silicon substrate. The Schottky-barrier diode has been made by depositing a gold film onto an n-type silicon substrate. These techniques have a high potential for making an ohmic-contact electrode with good adhesion. The alloy process can be eliminated from the fabrication of a photocell. Finally, the current status of solar-cell technology in Japan is reviewed.

Solar cells fabricated by ionised-cluster beam technology

It is shown that ionised-cluster beam deposition and epitaxial techniques are useful for the fabrication of photocells. A thin layer of single-crystal silicon and a very thin conductive metal film made by these techniques are used to obtain wide-spectrum sensitivity of the cells. The p-n junction diode has been made by n-type silicon epitaxy onto a p-type silicon substrate. The Schottky-barrier diode has been made by depositing a gold film onto an n-type silicon substrate. These techniques have a high potential for making an ohmic-contact electrode with good adhesion. The alloy process can be eliminated from the fabrication of a photocell. Finally, the current status of solar-cell technology in Japan is reviewed.

XXXIII. Noise in current-carrying ohmic conductors.

Abstract The mean-square noise current in a conductor which is in temperature equilibrium and carries a current I, is calculated on the assumption that the current is due to elementary carriers of charge e. The value obtained for the spectral density is {(2kT/R)+[2kT/R)2+(2eI)2]1/2}, where R, T, k are respectively resistance, absolute temperature and Boltzmann's constant. The interpretation of this result is that, over and above the ordinary thermal Nyquist noise, there is present an additional noise, of which the spectral density varies in square-law fashion according to (e 2R/kT)I2 for small I, and in linear fashion according to {(-2kT/R)+2eI} for large I. These predictions are compared with Bernamont's experimental results for thin metallic conductors, and the discrepancies are discussed.